Website: www.nrri.umn.edu/ NRRI Duluth // Laboratories and Admin // 5013 5013 Miller Trunk Highway, Duluth, MN 55811 // (218) 788-2694 NRRI Coleraine // Laboratories // P.O. Box 188 // One Gayley Avenue, Coleraine, MN 55722 // (218) 667-4201 NRRI REPORT OF INVESTIGATION OPPORTUNITIES OFFERED BY EMERGING HYDROMETALLURGICAL TECHNOLOGIES Submitted by: Shashi Rao, Matthew Mlinar, George Hudak, Kevin Kangas, and Dean Peterson Date: August 2022 Report Number: NRRI/RI-2022/10 Funding: Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR) Recommended Citation: Rao, S., Mlinar, M., Hudak, G., Kangas, K., and Peterson, D. 2022. Opportunities offered by emerging hydrometallurgical technologies: Report to the Legislative-Citizen Commission on Minnesota Resources. Natural Resources Research Institute, University of Minnesota Duluth, Report of Investigations NRRI/RI-2022/10. 170 p. Keywords: hydrometallurgy, critical metals, battery metals, carbon mineralization, mercury capture, waste resources, recycling, climate technology Natural Resources Research Institute University of Minnesota, Duluth 5013 Miller Trunk Highway Duluth, MN 55811-1442 Telephone: 218.788.2694 e-mail: nrri-reports@umn.edu Visit our website for access to NRRI publications. ©2022 by the Regents of the University of Minnesota All rights reserved. The University of Minnesota is committed to the policy that all persons shall have equal access to its programs, facilities, and employment without regard to race, color, creed, religion, national origin, sex, age, marital status, disability, public assistance status, veteran status, or sexual orientation. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies i Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Abstract Minnesota has abundant mineral resources, including deposits of iron, iron manganese, copper-nickel- cobalt-platinum group elements, titanium-vanadium, copper-zinc, gold with and without silver, sand, and aggregate. Commercial and industrial byproducts such as mine tailings, industrial residues, and waste electrical and electronic equipment also contain valuable mineral resources. To address significant environmental impact concerns associated with mining, collection and processing of these materials, new processing technology approaches with reduced water and energy consumption and minimal environmental footprints are needed to support production of value-added products. Emerging hydrometallurgical processing technologies offer promising opportunities. Hydrometallurgy techniques have a range of applications from extraction of high-value products from mineral and recycled materials to water remediation to generating secondary products for carbon sequestration. To evaluate the technical, economic, and environmental resiliency of emerging hydrometallurgical innovations, the Minnesota Legislative-Citizen’s Commission on Minnesota Resources (LCCMR) provided funding to the Natural Resources Research Institute (NRRI) to evaluate how to best support the development of emerging hydrometallurgical technologies in the state. To support this effort, NRRI evaluated: 1) A summary of perceived current and future hydrometallurgical needs of stakeholders based on a “voice of customer” (VOC) survey. 2) A discussion of how to apply hydrometallurgical capabilities to Minnesota-specific mineral and waste resources to maximize long-term economic, environmental, and social benefits and resilience. 3) A vision developed to advance Minnesota’s research capabilities in mineral characterization, mineral processing, extraction, and refining via hydrometallurgy that will lead to more efficient and effective utilization of Minnesota minerals and waste resources in the future. This research digs deeper into emerging applications of hydrometallurgical techniques in the production of value-added materials from a range of primary and secondary resources. The report also explores how application of these techniques to regional resources could potentially foster a more diversified minerals economy in Minnesota, develop treatment technologies to protect water resources, utilize regional resources for carbon mineralization, and supply materials required to build clean energy technologies. Acknowledgements The work highlighted in this project was made possible by a grant from the Legislative-Citizen Commission on Minnesota Resources (LCCMR) under M.L. 2019, First Special Session, Chapter. 4, Article. 2, Section. 2, Subdivision. 3 (r)). The authors thank Dr. Rolf Weberg for his thoughtful guidance as well as his unwavering support and encouragement throughout the life of the project. The authors also extend special thanks to Dr. Pat Schoff, Mr. Glenn Barr, Dr. Joyashish Thakurta, Ms. Anda Bellamy, Ms. June Breneman, and participants of the Voice of Customer Survey who gave their valuable time to carefully read the manuscript and provide us with feedback. The authors wish to thank the NRRI finance and administrative team for their financial, technical, and administrative assistance in managing the project. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies ii Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Executive Summary What will Minnesota’s minerals economy look like in 2050? What is the role of emerging hydrometallurgical technologies that will enable sustainable use of mineral and waste resources in Minnesota? The Legislative-Citizen Commission on Minnesota Resources (LCCMR) commissioned this study to identify and evaluate emerging hydrometallurgical technologies with applications for processing Minnesota mineral and waste resources while reducing water and energy use in an effort to minimize the industry’s environmental footprint. This NRRI study, “Opportunities Offered by Emerging Hydrometallurgical Technologies,” offers one possible vision for the development of the minerals economy. It also highlights major issues and trends that will shape global, national, regional, and state agendas up to 2050 and provides a framework to support the actions required. Hydrometallurgy is a branch of extractive metallurgy that relies on manipulating solution chemistry for the dissolution, concentration, and purification of metals or metal compounds from ores, concentrates, tailings, wastewater and various recycled and residual wastes. Techniques that complement hydrometallurgy include mineral characterization, mineral processing, wastewater treatment, pyrometallurgy, vapor metallurgy, and electrometallurgy. The primary applications for hydrometallurgical techniques include: ● Production of critical metals from primary mineral resources; ● Production of materials used in the construction of renewable energy technologies like rechargeable batteries, energy storage, solar panels, and wind turbines; and ● Extraction of metals from secondary resources like mine tailings, urban waste, metallurgical waste, manufacturing scrap, and various industrial residues that contain critical metals. Other emerging applications of hydrometallurgical techniques include: ● Removal of metallic and non-metallic contaminants from wastewater to protect land and water resources; and ● Production of secondary materials for climate change mitigation via carbon mineralization. This report includes: o An assessment of Minnesota’s mineral and waste resources that have the highest potential for hydrometallurgical processing. Key resources include: ○ Copper-nickel-platinum group element (Cu-Ni-PGE) resources of Duluth Complex. ○ Nickel-copper-platinum group element (Ni-Cu-PGE) resources present in the Tamarack Intrusive Complex. ○ Titanium-iron vanadium deposits that occur in oxide ultramafic intrusions (OUIs) along the western margin of Minnesota’s Duluth Complex. ○ Copper-zinc deposits and gold-silver deposits associated with greenstone belts. ○ Iron-manganese (Fe-Mn) deposits that occur in the Cuyuna District of east-central Minnesota. ○ Aggregate and byproduct resources that occur across the state that may contain recoverable quantities of critical metals. ○ Incinerator ash from Minnesota’s coal-burning power plants and waste-to-energy facilities, which can contain a variety of critical metals. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies iii Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance ○ Electronic waste (e.g., e-waste or waste electrical and electronic equipment), which can contain a variety of critical metals. o A review of challenges encountered by stakeholders during the commercial development of mineral and waste resources using hydrometallurgical technologies. Key challenges include: ○ Lack of research supporting the development of advanced processing techniques requiring less water and energy and reducing environmental footprints. ○ Lack of R&D support to advance the production of value-added products via hydrometallurgy from regional resources. ○ Absence of a regional laboratory to support the timely completion of economic and environmental impact assessments of emerging hydrometallurgical technologies. ○ Lack of diversification of research facilities supporting diversification of minerals economy in the state of Minnesota. ○ Lack of research to minimize mercury discharge from future industries to mercury- impaired waters. o A summary of emerging hydrometallurgical innovations that may resolve various challenges identified in the stakeholder engagement survey. These include: ○ Establishing a regional laboratory that advances the development of hydrometallurgical techniques with lower water and energy requirements and reduced environmental footprints. ○ Innovations that advance the production of value-added materials from regional resources; ○ Research and development that supports the production of secondary materials to support Minnesota’s climate mitigation strategies. ○ Innovations that promote regional production of critical metals from Minnesota resources. ○ A regional laboratory that provides data to support timely completion of environmental impact assessments of emerging innovations. ○ Research supporting the development of water remediation strategies to reduce mercury discharge from hydrometallurgical processing facilities. o A list of research priorities that support deployment of emerging hydrometallurgical technologies specifically for battery material production, critical minerals extraction, waste rock assessment, treatment technologies for heavy metal removal, and carbon sequestration. Key priorities include: ○ Define viable hydrometallurgical technologies to produce high-value materials from Minnesota’s mineral and waste resources; ○ Explore the potential applications for hydrometallurgical techniques to understand the environmental impact of waste rocks and tailings via accelerated aging; and ○ Understand the potential applications of hydrometallurgical techniques to create secondary products that could potentially allow CO2 sequestration. ○ Explore hydrometallurgical technologies to reduce mercury concentration from potential process waste to below 0.77 ng/L (the Fond du Lac Band standard). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies iv Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance o Identifying bench-scale and semi-pilot laboratory tools that will allow the State of Minnesota to conduct successful research for advancing the technological readiness level of emerging hydrometallurgical technologies. At a minimum, the following bench-scale and semi-pilot equipment and tools are necessary: ○ Advanced mineral processing tools like fine grinding, gravity separators, and flotation cells that allow beneficiation of mineral and waste resources. ○ Metal dissolution and CO2 sequestration tools like continuous stirred tank reactors and pressurized autoclave reactors. ○ Solution purification and contaminant removal tools that allow separation and purification of leach liquors using solvent extraction, ion exchange, and adsorption techniques. ○ Metal recovery tools to produce high-purity metal compounds using precipitation and electrowinning. ○ Waste rock characterization tools to help investigate leachate quality and dissolved metal flux from potential oxidation of waste rock, mine tailings, and/or electronic waste. ○ Column chromatography and column reactors for research on mercury and other heavy metal removal from potential mine discharges using novel sorbents. ○ The capital estimates for bench-top and semi-pilot laboratory prototypes range from $600,000 to $1.2 million. The personal, installation, and collaboration costs range from $300,000 to $400,000. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies v Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance TABLE OF CONTENTS Abstract .......................................................................................................................................................... i Executive Summary ....................................................................................................................................... ii List of Tables ............................................................................................................................................... vii List of Figures .............................................................................................................................................. vii Summary of Grant ......................................................................................................................................... 1 Summary of Intent .................................................................................................................................... 1 Report Layout ............................................................................................................................................ 1 Part 1: Brief Introduction to Hydrometallurgy.............................................................................................. 4 General Hydrometallurgical Processes ..................................................................................................... 8 Leaching ................................................................................................................................................ 8 Solvent Extraction ................................................................................................................................. 8 Ion Exchange ......................................................................................................................................... 8 Adsorption ............................................................................................................................................ 9 Precipitation .......................................................................................................................................... 9 Electrowinning ...................................................................................................................................... 9 Emergence of Hydrometallurgical Innovations in the United States ..................................................... 12 Early Drivers for the Adoption of Hydrometallurgical Techniques ......................................................... 12 Enactment of Clean Air Act ................................................................................................................. 12 Declining Ore Grade and Increased Ore Complexity .......................................................................... 13 Ability to produce high purity-value added products ......................................................................... 14 Energy, Water and Carbon Footprint ...................................................................................................... 14 Waste Solids Management and Mine Drainage ..................................................................................... 14 Iron control in Hydrometallurgy ............................................................................................................. 15 Sulfur Management in Hydrometallurgy ................................................................................................ 16 Waste Effluent Management .................................................................................................................. 16 Part II: List of Regional Resources Amenable to Hydrometallurgical Technologies ................................... 17 Part III: Opportunities and Challenges for Hydrometallurgical Technology Development ........................ 19 Summary of Intent .................................................................................................................................. 19 Stakeholder Engagement via Voice of Customer Survey ........................................................................ 19 Additional Needs of Stakeholders ...................................................................................................... 21 Part IV: Emerging Hydrometallurgical Technologies .................................................................................. 24 Emerging technologies with limited demonstration to Minnesota resources ....................................... 27 Part VI: Research Priorities for NRRI ........................................................................................................... 37 Part VII: Conceptual Design of a Hydrometallurgical Research Laboratory ............................................... 39 Summary of Intent .................................................................................................................................. 39 Hydrometallurgical Process Development .............................................................................................. 39 Bench-Scale Testing ............................................................................................................................ 39 Pilot-Scale Testing ............................................................................................................................... 39 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies vi Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Demonstration Plants ......................................................................................................................... 40 Laboratory Prototypes and Simulators ................................................................................................... 40 Battery Metal Production, Critical Metal Extraction, and Carbon Mineralization ............................. 40 Waste Rock Characterization .............................................................................................................. 40 Mine Water Remediation ................................................................................................................... 40 Hydrometallurgical Research Equipment ........................................................................................... 40 Part IX: Skill Sets Required to Sustain Hydrometallurgical Research .......................................................... 50 Aqueous Research Chemist/Metallurgist ............................................................................................... 50 Research Technician ................................................................................................................................ 50 Analytical Chemist ................................................................................................................................... 51 Part X: Collaborators and Potential Funding Opportunities ....................................................................... 52 Part XI: Summary and Recommendations .................................................................................................. 53 1. Minnesota Resources Amenable to Hydrometallurgical Processing .............................................. 53 2. Challenges and Opportunities Anticipated During Resource Development ................................... 54 3. Emerging Opportunities .................................................................................................................. 55 4. Key Research Priorities ................................................................................................................... 55 Conceptual Design of a Hydrometallurgical Research Facility ................................................................ 55 References .................................................................................................................................................. 56 Appendices .................................................................................................................................................. 60 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies vii Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance List of Tables Table 1. Comparison between hydrometallurgical and pyrometallurgical technologies ............................. 7 Table 2. General unit operations and unit processes in hydrometallurgy ................................................. 10 Table 3. Summary of emerging technologies and their potential applications to Minnesota resources ........................................................................................................................................ 29 Table 4. Alignment of stakeholder needs to NRRI's core competencies. ................................................... 35 Table 5. Laboratory equipment required to support a hydrometallurgical research facility. .................... 41 Table 6. Summary of budgetary estimate required to support hydrometallurgical research. .................. 45 Table 7. A comprehensive list of institutes and laboratories with hydrometallurgical research capabilities in North America. ........................................................................................................ 46 Table 8. Comparison of research capabilities of leading North American research institutes. ................. 47 List of Figures Figure 1. Potential applications for hydrometallurgical technologies to Minnesota resources. .................. 5 Figure 2. Role of hydrometallurgy in sustainable development. .................................................................. 6 Figure 3. Typical process flowsheet for a hydrometallurgical process ....................................................... 11 Figure 4. NRRI's vision for application of hydrometallurgical technologies to Minnesota resources. ....................................................................................................................................... 25 Figure 5. Hydrometallurgical technology categories and their relevance to Minnesota resources........... 26 Figure 6. Relevance of stakeholder issues to NRRI's core competencies. .................................................. 34 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 1 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Summary of Grant The University of Minnesota-Duluth Natural Resources Research Institute (UMD NRRI) was awarded a grant (M.L. 2019, First Special Session, Chapter. 4, Article. 2, Section. 2, Subdivision. 3 (r)) by the Legislative-Citizen Commission on Minnesota Resources (LCCMR) to identify and evaluate emerging hydrometallurgical technologies with applications for processing Minnesota mineral and waste resources. Summary of Intent The summarized intent for the grant is noted below. ● Identify and prioritize hydrometallurgical techniques that offer unique capabilities to: ○ extract high-value metal products from Minnesota mineral resources and mineral-based waste materials at high purity and reduced energy consumption with closed-loop water cycling systems; ○ allow collection of metallic byproducts for an enhanced economic and environmental benefit to Minnesota; and ○ enable a circular economy approach for metallic resources and waste streams. ● Engage industry and engineering collaborators across the state of Minnesota to identify and evaluate the relevance of current and emerging hydrometallurgical technologies. ● Establish a benchmark of current North American hydrometallurgical processing research capabilities and applicability to Minnesota resources. ● Provide a foundation for the concept and design development for a unique hydrometallurgical research facility at the NRRI Coleraine Laboratory. Report Layout Brief descriptions of sections of this report are listed below. • Part I: Brief introduction to hydrometallurgy o The report starts with a brief introduction to hydrometallurgy and the relevant unit processes. The section also provides a brief comparison of the hydrometallurgical process and the conventional (and complementary) pyrometallurgical smelting process. A visualization of potential applications of hydrometallurgical processes to Minnesota resources is also presented. • Part II: List of regional resources amenable to hydrometallurgical technologies o This section lists regional mineral and waste resources that have the potential to be upgraded to high value-added products using hydrometallurgical processes. • Part III: Opportunities and challenges for hydrometallurgical technology development o This part summarizes the key opportunities for hydrometallurgical process development in the state of Minnesota. It also summarizes the critical needs, wants, and expectations of stakeholders as gathered via the “Voice of Customer” survey. The section also highlights key challenges faced by stakeholders during the commercial development of resources using hydrometallurgical processes. • Part IV: Emerging hydrometallurgical technologies o A brief overview of emerging technologies in the areas of battery material production, critical metal extraction, carbon mineralization, and heavy metal capture are highlighted. The section also reviews emerging hydrometallurgical techniques that enable the production of value-added materials using less energy and water, and with a reduced environmental footprint. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 2 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance • Part V: Strategic fit of emerging technologies to the NRRI mission o This section describes how emerging technologies identified in Part IV align with the NRRI mission and how these emerging technologies are relevant to creating the minerals economy of the future in Minnesota. • Part VI: Research priorities for NRRI o This section lists the top research priorities that relate to the development, demonstration, and commercialization of emerging hydrometallurgical technologies in the state of Minnesota. Emphasis is given to creating solutions that use Minnesota’s mineral and waste resources in a manner consistent with the United Nations’ definition of “sustainability.” • Part VII: Conceptual design of a hydrometallurgical research laboratory o This section provides a list of bench scale equipment necessary to support the research priorities identified in section VI. • Part VIII: Benchmarking North American hydrometallurgical research facilities o This section lists the research capabilities of leading hydrometallurgical research laboratories in North America. • Part IX: Skill sets required to sustain hydrometallurgical research laboratories o This part of the report lists the skill sets and qualifications required to manage and sustain a hydrometallurgical research laboratory in Minnesota. • Part X: Collaborators and potential funding opportunities o Potential research collaborators and funding agencies are highlighted. • Part XI: Summary and recommendations o This section summarizes the key research priorities to advance the technology readiness level of emerging hydrometallurgical technologies. The section also lists the key research equipment and skill sets that are necessary to onboard and sustain hydrometallurgical research programs at NRRI. • Appendix A: Hydrometallurgical research equipment o A list of key laboratory equipment required to develop and demonstrate emerging hydrometallurgical technologies are highlighted in this section. • Appendix B: Emerging hydrometallurgical technologies o A detailed description of emerging hydrometallurgical technologies and their commercial advancements are listed in this section. The report identifies potential opportunities to apply these techniques to regional resources. • Appendix C: Commercial hydrometallurgical operations in North America o This section lists commercial North American operations that practice hydrometallurgical techniques to process copper, nickel, PGE, titanium, and manganese ores and concentrates. The section also lists facilities that use pyrometallurgical and electrometallurgical techniques in conjunction with hydrometallurgy. • Appendix D: Mineral resources of Minnesota o This section summarizes the regional mineral resources that are most suitable for hydrometallurgical processing. • Appendix E: Waste resources of Minnesota o A detailed description of regional waste resources that are most suitable for hydrometallurgical processing are summarized in this section. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 3 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance • Appendix F: Case study on hydrometallurgical process development at Long Harbor o This section reports on R&D work conducted by Vale to support the development, demonstration, and commercialization of hydrometallurgical processing of nickel- copper-cobalt concentrates at Long Harbor, Newfoundland. • Appendix G: Application of biohydrometallurgical technologies o This section reviews biological leaching processes practiced in base metal and precious metal extraction, and highlights opportunities to use biomass in metal recovery applications. • Appendix H: Application of hydrometallurgy to mine wastewater treatment o This section reviews hydrometallurgical processes used to remove metal and other inorganic contaminants from mine wastewater. • Appendix I: Historical hydrometallurgical investigations conducted by NRRI o Hydrometallurgical research work conducted by NRRI on various mineral resources is highlighted in this section. (Note: Where available, hyperlinks are provided.) NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 4 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part 1: Brief Introduction to Hydrometallurgy Metallurgy is the science and art of extracting metals from their ores, refining them, and preparing them for use (Schuhmann, 1952). Hydrometallurgy is a subdivision of extractive metallurgy that is reliant upon aqueous chemistry for the dissolution, concentration, and purification of metals or metal compounds from ores, concentrates, and various recycled or residual materials (Habashi, 1993). Some unique advantages offered by hydrometallurgical techniques are described below. • With the gradual depletion of ore grades of base metals, precious metals, and critical metals, it is becoming increasingly challenging to process lean and complex ores via conventional mineral processing and pyrometallurgical techniques. Hydrometallurgical techniques, on the other hand, were developed to extract metals from lean, complex, and low-grade ores. • Conventional pyrometallurgical processes such as roasting and smelting produce undesirable gaseous emissions, making them increasingly difficult to permit. Unlike pyrometallurgical processes, hydrometallurgical methods eliminate the emissions of sulfur dioxide while treating sulfide concentrates. However, acid mist from electrowinning tank houses and undesirable emissions from the solvent extraction circuit and CO2 emissions from limestone acid neutralization pose environmental, health, and safety concerns. • Hydrometallurgical techniques can produce high-purity metal or metal compounds in a variety of forms such as powders, nodules, and coherent surface deposits. • The waste liquors from hydrometallurgical processes can be regenerated and reused in metal extraction and purification stages. Figure 1 presents a hypothetical overview of potential applications of hydrometallurgical techniques to Minnesota’s mineral and waste resources. Figure 2 illustrates the roles that hydrometallurgical techniques could potentially play in delivering the United Nations sustainable development goals (UN SDG). Hydrometallurgical processes have grown in importance over the past few decades and assume a leading role in metals processing, but there are some significant challenges that are presented such as (Habashi, 1993): • Hydrometallurgical processes produce large volumes of waste effluents. Disposal and reuse of such wastes poses environmental challenges. • Reaction rates of hydrometallurgical processes are relatively slower compared to pyrometallurgical processes. Hence, throughput rates of hydrometallurgical plants are lower as compared to smelters. • Hydrometallurgical plants require special materials of construction due to the corrosive nature of some reagents. • In some instances, the higher cost of reagents and capital costs could potentially render the hydrometallurgical processes economically and environmentally unviable unless offset by factors like byproducts sale and recycling of reagents. A detailed comparison between hydrometallurgical and the traditional pyrometallurgical processes is shown in Table 1. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 5 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 1. Potential applications for hydrometallurgical technologies to Minnesota resources. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 6 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 2. Role of hydrometallurgy in sustainable development. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 7 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 1. Comparison between hydrometallurgical and pyrometallurgical technologies (adopted from Anderson, 2014). Metric Category Pyrometallurgy Hydrometallurgy Treatment of low-grade ores Process Less economical to process low-grade ores due to consumption of large amounts of energy to melt and separate gangue minerals Suitable for treating a wide variety of low-grade ores Reaction Kinetics Process Reaction rates are higher, as higher temperatures promote faster kinetics Significantly slower compared to pyrometallurgical processes Materials handling Process Equipment Requires vessels capable of handling molten metals, slags, and waste gas Requires vessels capable of handling corrosive reagents Economies of Scale Economics Suitable for large economies of scale, which requires large capital investment Hydrometallurgical techniques are suitable for smaller scale operation. Requires lower capital investment compared to new pyrometallurgical smelters Treatment of Secondary resources (Urban Waste) Waste Reduction Not suitable to treat urban wastes on a standalone basis. Requires a final hydrometallurgical or electrometallurgical process to upgrade the smelter products Suitable to produce high-value-added products from secondary metal resources Environmental consideration Social License Requires special emission control systems to capture waste gas and dust generated from processes Requires safe handling and treatment of waste effluents Treatment of sulfide ores Process Generates large volumes of SO2 that must be captured and converted to sulfuric acid Eliminates generation of sulfur dioxide. Technology aids in recovery of sulfur in elemental form Solid residues Waste Reduction Process residues such as dusts, slags, and others may contain valuable metals that require further processing Solid residues from hydrometallurgical processes requires washing, neutralization, and related treatment before discarding it to tailings storage facility Toxic gasses Environmental Impact Generates toxic gasses that require specialty emission treatment and control systems to protect the ambient air quality Toxic fumes are generated in relatively small quantities in the reactors NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 8 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance General Hydrometallurgical Processes Metallic elements found in mineral concentrates, waste tailings, and industrial wastes can be transformed into high-purity materials by a series of hydrometallurgical processes like metal extraction, solution purification, and metal recovery. The following section provides a brief description of major hydrometallurgical unit operations like leaching, solvent extraction, ion exchange, carbon adsorption, precipitation, and electrowinning processes. The processing flowsheet and operating conditions for each of these processes are unique to the target metal under investigation (Habashi, 1993). The commonly practiced hydrometallurgical unit processes and unit operations for metal extraction are shown in Table 2, and a typical sequence of operation for a hydrometallurgical operation is shown in Figure 3. Leaching Leaching is carried out to dissolve the whole, or some part, of the feed material containing various metallic minerals. The selectivity of dissolution of an element depends on the nature of the reagent, while the kinetics of the reaction depends on factors such as temperature, pressure, concentration of the reagent, pulp density, residence time, and degree of aeration of the leaching reagent. Other than water, leaching agents commonly used are categorized into following areas: acids, bases, aqueous salt solutions (Habashi, 1993). The selection of appropriate leaching agents depends on following criteria: • Solubility: the mineral or metal of interest should have large and rapid solubility in the leaching reagent. • Selectivity: An ideal reagent will extract only desired constituents present in the material. • Regeneration: Ability to regenerate reagents for reuse in the leaching step minimizes reagent consumption. • Materials of construction: Highly corrosive leaching agents require specialty alloys such as stainless steel, titanium, or Hastalloy for safe handling. • Cost: Reagents should be economical and readily available. Pregnant leach solutions contain dissolved metal or metallic compounds that require further processing. In most cases, this involves chemical separation in which dissolved metals are concentrated, purified, or removed. A range of methods are employed and comprise processes such as solvent extraction, ion exchange, adsorption, membrane filtration, and precipitation. Solvent Extraction Solvent extraction (or commonly known as liquid-liquid extraction) is a process in which dissolved metal or metal ion species are extracted from the aqueous phase by contacting it with an organic solvent. The process is based on the immiscible nature of the solvent in which metal or metal ion complex would dissolve completely to form organometallic complex, while the other unwanted ions remain in the aqueous phase. During the process, the organic solvent and the aqueous phases are intimately mixed and subsequently allowed to disengage via settling. Subsequent to separation of two liquids, the metal species are transferred back to the aqueous phase in a concentrated and purified form by adjusting the solution conditions to reduce the metal solubility in the organic phase via a process called stripping (Free, 2013; Habashi, 1993). Ion Exchange In the ion exchange process, the resin is made to absorb a suitable ion of the desired metal ion or complex through an ion-exchange reaction. The absorbed ion is then stripped into solution by employing a process called elution. The stripping solution is called eluant, and the solution into which the ions have been stripped is known as eluate (Free, 2013). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 9 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Ion exchange gained significance during the World War II Manhattan Project when it was industrially adopted to recover uranium from leach liquors. The major commercial applications of ion exchange include base metals (copper, cobalt, and nickel), gold, and uranium extraction. Other areas where ion exchange has found a niche include rare earth metal extraction, PGM recovery, and lithium extraction from brines (Habashi, 1993). Adsorption Adsorption on activated carbon is predominantly used for concentrating gold and silver from cyanide leach solutions. Activated carbon is typically made using coconut shells, but other materials like peach pits, nut shells, sugar, wood, and coal are also used. Adsorption is typically carried out in countercurrent columns or tanks filled with activated carbon. When adsorption is complete, the pulp is screened to separate the activated carbon, and then the metal ion complex is stripped from carbon using a caustic cyanide solution at higher temperature. The stripped solution is subjected to metal recovery process to recover the metal. Subsequently, the activated carbon is subjected to regeneration by thermal activation to remove organic contaminants and subjected to acid wash to remove inorganic constituents like carbonates (Free, 2013). Precipitation Precipitation is used to purify or concentrate pregnant leach solutions by removing specific impurities by adjusting the pH of the solution. The differences in solubilities of metals as a function pH facilitates separation of species (Free, 2013). Electrowinning In electrowinning, the dissolved metal is recovered from the solution using electrolysis. The metal is recovered by applying a potential to drive electrochemical reactions. An external electricity source supplies the potential and current. The dissolved metal is reduced, and deposits at the cathode and other ions or molecules are oxidized at the anode, which is made from inert insoluble conductor. The electrodes are typically placed in an electrolyte- or ion-conducting medium with sufficiently high conductivity. Metals that are primarily produced via electrowinning include copper, nickel, cobalt, zinc, aluminum, lithium, titanium, indium, tantalum, niobium, hafnium, zirconium, molybdenum, vanadium, beryllium, chromium, cadmium. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 10 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 2. General unit operations and unit processes in hydrometallurgy (adapted from Habashi, 1993). Unit Process Unit Operations Purpose Extraction • In situ leaching • Heap/Dump leaching • Agitation leaching • Pressure leaching • Bioleaching Selective dissolution of metals from feed material using a solvent Purification/Concentration • Precipitation • Ion Exchange • Solvent Extraction • Adsorption • Membrane filtration Concentration or purification of leach solutions before metal recovery Recovery • Electrowinning • Cementation • Electrorefining Recovery of pure metals or metal compounds from concentrated solutions NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 11 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 3. Typical process flowsheet for a hydrometallurgical process (adapted from Free, 2013). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 12 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Emergence of Hydrometallurgical Innovations in the United States While early roots of hydrometallurgy are shrouded in history, the modern day growth in the importance of hydrometallurgical innovations originates from the discovery of transuranium elements for the Manhattan Project at the University of Chicago Metallurgical Laboratory (Met Lab). Early notable hydrometallurgical inventions stem from the works of Nobel Laureate Dr. Glenn T. Seaborg at the Met Lab, where he led a team that was responsible for devising a hydrometallurgical process for the separation, concentration, and isolation of plutonium from spent fuel using a bismuth-phosphate precipitation process. (U.S. Department of Energy- Office of History and Heritage Resources, 2005). This process was later scaled up by a billion fold by DuPont Corporation at the U.S. Atomic Energy Commission’s production plant in Hanford, WA (Seaborg, 1965). Other significant hydrometallurgical inventions from the Manhattan Project related to rare earth element and uranium extraction, which is contemplated as the starting point of the present great interest in the use of ion exchange and solvent extraction methods for inorganic and radiochemical separations (Anderson, 2014). Another significant breakthrough that resulted in the far-flung adoption of hydrometallurgical processes beyond the nuclear industry was attributed to the invention of selective solvent extractants by Minnesota-based General Mills Chemical Company. Pioneering work of National Academy of Engineering inductee Joe E. House (then head of General Mills Chemicals’ Minerals Industry Division) in the 1960s sparked a fundamental shift in the way the worldwide copper industry operates today. House and a team of chemists at the General Mills developed an extractant – trademarked LIX – capable of extracting copper from a solution while leaving behind other metals dissolved in the same solution (National Academy of Engineering, 1998). As a direct result of this work, copper mineralization that was previously classified as waste is now mined and economically processed. In 2017, solvent extraction and electrowinning accounted for more than 50% of U.S. copper production and more than 20% of copper production worldwide (USGS, 2017). Since these early discoveries, hydrometallurgical techniques have been applied extensively not only for the separation and extraction of non-ferrous metals, but also in water purification, wastewater treatment, and environmental remediation (Free, 2013). Today, hydrometallurgical processes are widely used in the synthesis of battery materials, photovoltaic materials, automotive catalysts, fertilizers, electro optic materials, medical device substrates, etc. (Free, 2013). Early Drivers for the Adoption of Hydrometallurgical Techniques Enactment of Clean Air Act Prior to widespread industrial adoption of hydrometallurgical technologies in the U.S., high-temperature smelting and refining technologies were the prominent method of producing non-ferrous metals like copper, molybdenum, lead, and zinc. Prior to the enactment of the Clean Air Act, these smelters were the major sources of sulfur dioxide, metal fumes, nitrogen oxide, and carbon monoxide in North America (Free, 2013). Uncontrolled smelting practices also emitted hazardous air pollutants like lead, arsenic, mercury, zinc, cadmium, beryllium, antimony, and selenium into the ambient air (Free, 2013). Because smelting and refining processes require high temperatures to reduce the mineral concentrates into pure metal and to refine metals and alloys (for example, iron melts at 1536 °C, copper melts at 1083 °C, and aluminum melts at 660 °C), many other metals and metal compounds volatilize into the waste gas streams (for example, boiling points of mercury, cadmium, zinc, arsenic, and selenium are 357 °C, 765 °C, 906 °C, 613 °C, and 685 °C respectively). As atmosphere around smelters became more noxious, SO2 emissions came under severe scrutiny as a significant contributor to air pollution and acid rain. The Clean Air Act amendments of 1977 established national ambient air quality standards (NAAQS) for emissions of air pollutants including SO2 that endangered public health and welfare (Free, 2013). The enactment of the Clean Air Act mandated smelters to install pollution control equipment to reduce NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 13 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance sulfur dioxide emissions. To meet these standards, most smelter operations in North America installed gas cleaning and acid plants to demonstrate compliance with emission limits set by the Clean Air Act (Parameswaran, et al., 2018). However, gas cleaning and acid plants required a relatively high (at least 4 percent) SO2 concentration in the off-gas for economical operation and compliance with pollution limitations. Waste gases with weaker SO2 concentrations, such as those from the older reverberatory furnaces, were not suitable for conversion of SO2 into sulfuric acid. The transition from reverberatory furnace to the modern flash and electric arc furnaces led to the production of strong sulfur dioxide concentrations in off-gas that were amenable for conversion to sulfuric acid, thus paving a way for smelters to eliminate a larger percentage of the sulfur dioxide emissions (Parameswaran, et al., 2018). An example of this modern advancement is the smelter constructed by Rio Tinto on the shores of the Great Salt Lake in Utah, which is designed to capture in excess of 99.9% of the sulfur that enters in the feed (Metso Outotec , 2017). Although the transition from reverberatory to modern furnaces and emission control technologies brought social, environmental, and improved operational benefits, it also cost the domestic copper industry enormous capital expenses, which led to closure of significant domestic smelting capacity. For instance, U.S. primary and secondary copper smelter production drastically reduced from a 1981 level of nearly 1.4 million tonnes to about 0.5 million tonnes in 2015 (U.S. Congress, Office of Technology Assessment, 1990; USGS, 2017). Besides shutting down inefficient smelters with old-fashioned reverb furnaces, the copper industry was forced to consider radically different technologies to comply with stringent regulations. The responses of the copper industry to the Clean Air Act were twofold. The first was to turn to oxide minerals, which contained no sulfur, and that route led to the development of solvent extraction and electrowinning processes. The second was to subject sulfide minerals to processes like bio-hydrometallurgy and pressure hydrometallurgy that turned the sulfur present in the ore into elemental sulfur or gypsum instead of gaseous SO2. By 2017, 52% of the refined copper production in the U.S was produced via solvent-extraction and electrowinning technologies (USGS, 2017). Declining Ore Grade and Increased Ore Complexity The ore grades of base metal ores like copper and nickel have been gradually declining around the world. For example, in the early 1900s the average copper ore grade processed in the United States was 2%, but by the end of the 20th century ore grade had declined to 0.5% and has diminished to less than 0.5% today (Izatt, et al., 2014). The industry’s response to this decline was three-pronged. First, declining ore grades led to greater use of hydrometallurgical processes, which have greater tolerance for impurities compared to smelting technology. For instance, copper in the low-grade dumps was unrecoverable by the conventional smelting process and hence discarded as waste (Brierley, 2014), but copper could be extracted from low-grade oxide ores and some sulfidic ores through leaching, solvent extraction, and electrowinning technologies (SX-EW). Second, the copper ores that contained low levels of iron were better suited for hydrometallurgical processing, but copper ores that contained higher levels of iron were commonly processed using the pyrometallurgical route because the iron enabled them to be concentrated quite easily while utilizing the heat generated from the exothermic reaction resulting from oxidation of iron and sulfide minerals. Lastly, companies that aimed at producing a concentrate for sale to a smelter (in order to minimize capital costs, operating costs, and permitting requirements) could not produce a concentrate of sufficient grade to carry the transport costs at an acceptable recovery. In this case, potential hydromet routes were deemed less capital intensive than smelting. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 14 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Ability to produce high purity-value added products Hydrometallurgical processes gained prominence because of their ability to produce high-purity finished products for the nuclear industry. During the Manhattan project, high-purity rare, refractory, and nuclear metals like uranium, plutonium, zirconium, hafnium, thorium, and beryllium were extensively generated using hydrometallurgical processes (Anderson, 2014). Today, hydrometallurgy is applied to extract a wide variety of pure metals (e.g., Al, Mg, Mn, Co, Pt, Pd, Ag, Au, Ni, Cu, REE, Li, In, Zn), powders, or compounds from a variety of feedstock including run-of-mine ores, concentrates, waste dumps, mine wastewater, matte, metallurgical waste, and urban waste products (Anderson, 2014). Energy, Water and Carbon Footprint As orebodies of metallic minerals become increasingly dilute and complex, extraction of metals from these leaner ore bodies and resulting process streams require increased energy consumption and associated greenhouse gas emissions. The increased energy consumed derives primarily from the need in the mining and mineral processing stages to move and treat additional material to produce the same amount of final product (Izatt, et al., 2014). A further consequence of the increased energy requirement is increased greenhouse gas emissions arising from the consumption of fossil-derived energy. Paralleling this increased energy and greenhouse gas emissions is an increased requirement for water to treat the additional gangue materials. The mining and processing of metals utilize about 7% of total world energy and 0.03% of total world water (Izatt, et al., 2014). Therefore, it is of paramount importance that any new technologies proposed to treat such low grade resources have improved metal extraction efficiencies coupled with lower energy, water, and environmental footprint. To validate the benefits of such emerging technologies, they must be compared to current lifecycle performance benchmarks for energy, water, and greenhouse gas emissions intensity, which will indicate the likely scope for reducing the environmental footprint. In light of increasing challenges, sustainable hydrometallurgical technologies will likely be those that can recover metals with higher energy and water efficiency and superior yield and purity while simultaneously recovering multiple metals from the same stream (Izatt, et al., 2014). Waste Solids Management and Mine Drainage Mining lean deposits with declining ore grades produces higher amounts of mine waste (tailings plus waste rock) and increased consumption of energy, water, and chemicals. It is estimated that 6.4 x 109 metric tons of ore is extracted annually from the Earth (2004), of which > 90% is discarded as mine and mill wastes (Izatt, et al., 2014). When hydrometallurgical processes are employed to process lean ores, the process residues and waste solutions may require appropriate treatment before discharging to the surrounding environment. While waste generated by pyrometallurgical processes is relatively stable for ambient storage, solid residues and bleed aqueous solutions from hydrometallurgical processes are generally not stable because of the presence of soluble metal species. Hence, disposal in tailings may be hazardous because of the danger of contaminating surface waters in the event of tailings dam failure (Government of British Columbia, 2014). The occurrence of sulfide minerals such as pyrrhotite, pyrite, and chalcopyrite in tailings also presents environmental challenges. Under appropriate conditions these minerals may react with oxygen and water to produce sulfuric acid, which can solubilize other minerals and release metal ions like arsenic, antimony, bismuth, lead, zinc, mercury, etc. into the solution (AMIRA International, 2002). Moreover, processing low grade ore bodies tends to be water intensive, but improved liquid-solid NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 15 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance separation methods that facilitate reuse of water may reduce consumption of freshwater in mining operations. Iron control in Hydrometallurgy Iron is the fourth most abundant material present in Earth’s crust. Iron occurs in the crystal structure of over 600 minerals. Iron is present in non-ferrous ores as ore minerals, gangue minerals, and solid solution minerals. In ore minerals of major nonferrous metals (Cu, Ni, Co, PGM, Mn, and Ti), iron is present as an essential constituent of a mineral used as a source of another metal. Examples include ilmenite and titanomagnetite for titanium; chalcopyrite and bornite for copper; pentlandite and nickeliferous limonite for nickel; and rhodonite and rhodochrosite for manganese. In gangue minerals, iron is an essential constituent of a mineral that is undesirable in the ore. Examples include pyrrhotite and pyrites, which are common gangue minerals present in base metal ores. Moreover, iron oxides, iron silicates, and iron carbonates are abundantly present as gangue minerals in many oxidized non-ferrous ores. Finally, in solid solution minerals, iron substitutes an essential element either in ore or gangue minerals. Examples include sphalerite and cobaltite (Monhemius, 2016). During hydrometallurgical processing of major non-ferrous ore minerals, iron presents the following challenges and opportunities: • The Pourbaix diagram for the Fe-H2O system indicates that iron in the ferrous oxidation state is soluble in highly acidic to mildly alkaline pH conditions, whereas ferric iron is soluble only in acidic solutions (pH < 3) and oxidizing conditions (Eh > 0.77 V). Therefore, while subjecting non- ferrous ore minerals to leaching, iron present in the ore mineral is readily soluble in the leach solution along with other metals of interest. As a result, iron removal from the solution becomes an essential prerequisite before solution purification and metal recovery steps (Monhemius, 2016). • The narrow solubility range of ferric iron in the Pourbaix diagram indicates that iron can be separated from the solution by oxidizing it to the ferric state followed by increasing the pH of the solution to greater than three. This causes the iron to precipitate as ferric hydroxide, which is relatively insoluble under specific pH and electrochemical potentials (Monhemius, 2016). Unlike fayalite, disposing of ferric hydroxide precipitates from hydrometallurgical processes in ways that satisfy regulatory standards is of paramount importance to both existing and developing hydrometallurgical technologies. • In smelting processes used for the production of non-ferrous metals, iron present in the smelter feed ends up in the slags as fayalite, ferrous silicate (Fe2SiO4), together with many other deleterious impurity elements. Fayalite is chemically and environmentally inert material posing minimal risk to the local surroundings (Monhemius, 2016). • Monhemius (2016) illustrates the huge scale of iron waste generated by hydrometallurgical processing of copper and zinc sulfide concentrates, estimating that a typical copper concentrate consists of 30% Fe and 25% Cu, compared with a typical zinc concentrate with around 10% Fe and more than 50% Zn. Thus, a ton of electrowon copper produced via hydrometallurgical means would necessitate the disposal of around six times as much iron as that arising from the production of a ton of electrolytic zinc. • Monhemius (2016) comments that it is not cost effective to use hydroxide precipitation to remove more than about 1 to 2 g/l of ferric iron from process solutions. This is primarily because NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 16 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance iron hydroxide precipitates have a tendency to form gelatinous compounds with large surface area that are difficult to filter and often trap valuable elements in their crystal structure. Sulfur Management in Hydrometallurgy Historically, high-temperature processing of sulfide concentrates of Cu, Zn, and Pb release sulfur dioxide into the ambient atmosphere. Following the introduction of the Clean Air Act, sulfur dioxide emissions were sequestered and converted into sulfuric acid. The development of hydrometallurgical processes in the 1960s facilitated the production of elemental sulfur instead of sulfur dioxide or sulfuric acid. In hydrometallurgical processes, sulfide minerals under oxidizing conditions in acid media dissociate into elemental sulfur, while the metallic element solubilizes into the solution (Habashi, 1996). Elemental sulfur in hydrometallurgical residues represents both a disposal challenge and a byproduct recovery opportunity. Sulfur and related sulfur compounds in waste tailings could potentially generate acid and cause pH changes in surface water bodies if sufficient neutralizing minerals are absent. Therefore, recovery of sulfur from the residue not only mitigates the volume and reactivity of the residues but also presents opportunities in byproduct sale (Conard, 1992). With stakeholders increasingly aware and pro- active about the residue and tailings generated from hydrometallurgical facilities, emerging technologies should invariably evolve to meet the challenges of waste management. For leach residues with significant amounts of elemental sulfur, known processes such as flotation and hot filtration are preferred technologies for byproduct recovery. Waste Effluent Management As mining operations evolve from processing high-grade ores to low-grade sulfidic mineral resources, the volume of surface material mined, water consumption, and the wide range of contaminants that appear in wastewater increases exponentially. To meet the strict regulatory limits of contaminants in mine discharge, the industry is challenged to investigate and develop cost-effective technologies to reclaim, reuse, and recycle mine wastewater prior to discharge. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 17 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part II: List of Regional Resources Amenable to Hydrometallurgical Technologies In this section, mineral and waste resources potentially amenable to hydrometallurgical processing have been identified. Hydrometallurgical techniques can potentially facilitate: 1) production of value-added materials used in renewable energy technologies like rechargeable batteries, solar panels, fuel cells, and wind turbines; 2) production of critical metals from mineral and waste resources; 3) remediation of inactive or closed processing facilities to protect land and water resources; and 4) production of secondary products for CO2 sequestration via carbon mineralization. Brief descriptions of these resource categories are presented here, and detailed descriptions are shown in Appendix B. ● NI 43-101 compliant mineral resource estimates for many of the Duluth Complex contact-type Cu-Ni-PGE magmatic sulfide deposits total 9.57 billion metric tons with average grades of 0.406% Cu, 0.126% Ni, and 0.326 g/t Pt-Pd-Au. Major deposits include Birch Lake, Maturi, Mesaba, NorthMet, Serpentine, and Spruce Road (Polymet Mining, 2019; Duluth Metals Corp, 2014; Teck Resource, 2019). ● The mineral resource estimate for the Tamarack Intrusive Complex conduit-type Ni-Cu-PGE sulfide deposit in east-central Minnesota is 11.09 million metric tons with average grades of 0.8% Cu, 0.1393% Ni, and 0.223 g/t Pt-Pd-Au (Talon Metals, 2021). ● Minnesota’s OUI-associated Ti-Fe-V deposits include: 1) Longnose, with a NI 43-101 indicated resource of 58.1 million tons averaging 16.6% TiO2 (inferred 65.3 million tons averaging 16.4% TiO2) based on 27 drill holes and using a cutoff grade of 8% TiO2; 2) Titac, with a NI 43-101 inferred resource of 45.1 million tons averaging 14% TiO2 based on 32 drill holes and using a cutoff grade of 8% TiO2 ; and 3) Water Hen, with a crudely estimated 62 million tons averaging 14% TiO2, based on 37 drill holes (Minnesota Minerals Coordinating Committee, 2016). ● The iron formations and associated ore deposits of the Cuyuna iron range in east-central Minnesota contain appreciable quantities of manganese (Schulz, et al., 2017). Lewis (1951) estimated that 455 million metric tons of manganiferrous iron formation containing 2 to 10 percent manganese were available to open-pit mining to a depth of 45 meters. Beltrame et al., (1981) estimated a minimum of 170 million metric tons of manganiferrous rock with an average grade of 10.46 weight percent manganese. The manganese estimates are not as reliable because data used to make these estimates were prepared for different reasons at different times, using different databases and methodologies. ● Minnesota produces a wide variety of aggregates and byproducts (Minnesota DNR, 2022). The lithogeochemistry of these materials is currently being compiled so that analysis for potential resources amenable to hydrometallurgical processing can be evaluated. ● In Minnesota, eight waste-to-energy (WTE) facilities generate electricity by combusting mixed municipal solid waste (MMSW) and refuse-derived fuel (RDF). Incinerator ash from these facilities typically contains metals like arsenic, cadmium, chromium, lead, mercury, selenium, nickel, copper, tin, silver, barium, boron, and zinc (Michaels & Krishnan, 2018). ● Coal combustion residuals (CCR) generated from coal-fueled heat and power plants typically contain metals such as antimony, arsenic, barium, beryllium, cadmium, chromium, lead, mercury nickel, selenium, silver, and thallium (Environmental Protection Agency, 2015). ● Electronic waste, referred to as e-waste or waste electrical and electronic equipment (WEEE), contains critical metals like cobalt, lithium, rare earth elements, gallium, germanium, tantalum, NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 18 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance tungsten, platinum, and palladium. In Minnesota, approximately 199.4 million pounds of household electronic waste was collected for recycling between 2013 and 2018 (Minnesota Pollution Control Agency, 2021). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 19 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part III: Opportunities and Challenges for Hydrometallurgical Technology Development Summary of Intent NRRI conducted a “Voice of Customer” (VOC) survey involving 20 external participants. The purpose of this stakeholder engagement was to: ● better understand the current and future needs of Minnesota’s minerals industries; ● understand current hydrometallurgical technologies and plant practices; ● inform research strategies and prioritize technology development; and ● assess NRRI’s value proposition hypotheses: o Hydrometallurgical processes will play an important role in the treatment of the state’s base, precious, and critical mineral resources and waste resources. o NRRI’s hydrometallurgical R&D capabilities will enhance the competitiveness of the minerals industry, diversify the state’s minerals industry, and address environmental issues related to mineral extraction. The VOC survey was accomplished through interviews with a broad range of stakeholders around the country. These included current or prospective mineral/metal producers, metal recyclers, hydrometallurgical R&D labs, engineering and technology providers, consultants, academia and educators, regulators, and federal agencies. Stakeholder Engagement via Voice of Customer Survey The following section summarizes the critical needs, wants, and expectations of stakeholders as gathered via the VOC survey. ● Value-added products: Many prospective miners envision shipping mineral concentrates to international markets for further refining. However, due to rising transportation and toll smelting and refining costs, some miners believe that international shipping is not sustainable. Additionally, prospective miners noted difficulties in producing smelter-grade concentrates via flotation technologies from some of the resources in the Duluth Complex. To overcome these challenges, some prospective miners plan to employ hydrometallurgical techniques to produce value-added products from nickel and PGE concentrates. Others are evaluating the feasibility of producing battery-grade materials from high-grade Ni-Cu-PGE mineralization (e.g., Tamarack deposit, Aitkin County). ● Protecting water resources and mitigating mine drainage impacts: Regulatory agencies noted that any research to produce byproducts and/or reduce potential pollutants from mine wastewater could help with both real and perceived impacts of mining. Prospective miners mentioned that some of their current efforts to understand and mitigate mine drainage challenges include evaluation of desulfurization techniques, dry stacking of waste tailings, and removal of selenium from mine wastewater. ● Critical minerals research: Several participants noted the current United States dependency on imports for domestic consumption of critical metals as indicated in the USGS Mineral Commodity Summaries1. The USGS noted the need for a coordinated, long-term program to maximize the nation’s understanding of subsurface critical mineral resources and potential recovery of critical metals from historical metal mining waste, and in 2019, initiated the Earth Mapping Resources Initiative Program (Earth MRI). The USGS stated that such efforts would 1 See USGS Mineral Commodity Summaries NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 20 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance enhance the understanding of domestic resources of critical minerals, energy resources, groundwater resources, and geologic hazards. The USGS also stressed the need for partnerships with academia to determine the feasibility of extracting byproduct mineral commodities, such as critical minerals, from mine tailings and subsurface critical mineral resources2. ● Diversification of minerals economy: Some respondents indicated that diversification of the minerals sector economy in Minnesota would lessen the negative impact of iron mining downturns. While discussing innovative solutions to diversify the minerals sector economy, participants indicated that hydrometallurgical techniques would facilitate the production of value-added products from Minnesota’s mineral resources and enhance the royalty value of minerals owned by the State (e.g., School Trust Fund, University Trust Fund). A few participants believe that public concerns related to social acceptance of hydrometallurgical techniques could potentially be alleviated by making current and future research data readily accessible to the public. ● Need for advanced processing and environmental characterization laboratory: o Due to the lack of advanced research and development (R&D) facilities in Minnesota, stakeholders, including prospective miners, school trusts, and mineral rights holders, rely on international laboratories to support their geometallurgical, advanced processing, and environmental testing programs. The COVID-19 pandemic and closure of international borders resulted in lengthy delays to complete scientific studies. o Participants noted that hydrometallurgical processes are widely used in the extraction of base metals, precious metals, and critical metals. However, barriers to adoption of hydrometallurgical processes in Minnesota do not arise from its technological risks, but rather from the inherent risks of water pollution occurring from mining activities. Participants acknowledged that predicting and managing the occurrence of mine drainage to minimize risks to human and environmental health is one of the key challenges facing the mining industry. For this reason, each mineral deposit is assessed on its own merits to ensure that waste is managed appropriately as part of a mine material characterization program. Participants noted that the tools needed to estimate the magnitude of the risk are not readily available in Minnesota. o Prospective miners noted that bench- and pilot-scale testing is required throughout the development of a mineral deposit to minimize risk that emerging technologies can bring. Moreover, embedding these tests into the design phase ensures that risks are identified early, allowing stakeholders to make well-informed decisions, and if needed, to adopt technologies to meet statutory requirements. ● Alternatives to hydrometallurgical techniques: Participants noted there has been a steady decline in smelter production in the United States since the 1980s. The reasons cited for smelter production decline include: 1) the need to install expensive emission control technologies to meet the stringent emission standards in the United States; and 2) the steady decline in ore- grade in the United States. To meet stringent emission standards, smelters demand a higher- grade concentrate (e.g., Cu, Ni grade) and have a low tolerance for impurities such as arsenic, selenium, mercury, cadmium, bismuth, antimony, lead, zinc, fluorine, etc. As a result, smelters are not widely used to process low-grade ores. In contrast, participants noted that low- 2 See USGS critical mineral recovery NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 21 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance temperature processes like hydrometallurgical techniques have a high tolerance for impurities present in low-grade ores. ● Reuse and recycling of critical metals: The U.S. Department of Energy’s Advanced Manufacturing Office (AMO) states that its research focuses on four areas: 1) diversifying supplies: 2) developing substitutes; 3) driving reuse and recycling; and 4) crosscutting research. AMO officials noted that there is a growing need to eliminate and reduce reliance on rare-earth metals and other materials critical to the success of clean energy technologies. Additionally, AMO asserts that a domestic supply chain would reduce the U.S dependence on foreign sources for critical metals. To support these efforts, AMO funds the Critical Materials Institute (CMI), whose research focuses on recycling rare earth materials, battery materials (lithium, cobalt, manganese, and graphite), indium, and gallium. ● Timeline associated with environmental review and permitting process: Minnesota’s lengthy timeline to complete environmental review and permitting processes compared to other states or nations was a common concern cited by stakeholders. Many participants noted that, while Minnesota’s review process is intended to identify and address environmental issues, the process can be stalled or delayed over issues that lack regulatory clarity, and this often results in extensive review or even litigation, either of which can significantly increase the time required to complete permitting in Minnesota. Additional Needs of Stakeholders In addition to identifying stakeholder needs via structured interviews, NRRI identified broader societal needs via an ethnographic study. The insights from this study are summarized below. ● Mercury impaired waters: The Final Environmental Impact Statement (FEIS) for the NorthMet Project states that the project would deposit 164 pounds of mercury in the hydrometallurgical residue facility (HRF) each year. The report states that over the course of the proposed 20-year mine life, the operation would deposit up to 3,280 pounds of mercury in the HRF along with other metals like arsenic, manganese, copper, cobalt, and lead (Minnesota Department of Natural Resources, United States Army Corps of Engineers, United States Forest Service, 2015). The Fond du Lac Band of Lake Superior Chippewa is concerned about the impacts of HRF waste release on wetland, drinking water supplies, wild rice, fisheries, and public health downstream in any direction of the proposed mining project in the event of a tailings dam failure at the proposed NorthMet’s HRF waste facility (Fond du Lac Band of Lake Superior Chippewa v. Thiede, Calkins, Polymet Mining Inc, 2020). Moreover, the FEIS points out that the wastewater treatment facility at the proposed NorthMet project would be designed to meet water quality based effluent limits that are protective of the Great Lakes Initiative (GLI) chronic wildlife standard of 1.3 ng/L mercury, but this limit exceed the Fond du Lac Band’s human health chronic standard of 0.77 ng/L (Minnesota Department of Natural Resources, United States Army Corps of Engineers, United States Forest Service, 2015). Furthermore, the existing water quality data collected by the MPCA near the NorthMet project indicate that mercury values consistently exceed Class 2B water quality standards in many of the lakes and rivers in the NorthMet Project Proposed Action area. Because of this, the Fond du Lac Band is concerned that any new or expanded discharges to the St. Louis River upstream may adversely affect mercury bioaccumulation in fish in the St. Louis River. Mercury bioaccumulation is a particular concern to tribal authorities, as many tribes rely on fish for subsistence and cultural practices. Under the Clean Water Act (section 401) or Clean Air Act (section 301 (d)), Anishinaabe Tribes can enact water or air quality standards for the reservation when discharges upstream or upwind of a reservation have the potential to exceed those standards (U.S. Environmental Protection NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 22 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Agency, 2021). Since the enactment of section 301(d) of the Clean Water Act, in-stream mercury concentrations in the St. Louis River have been exceeding the Fond du Lac Band’s human health chronic standard (Fong, 2022). ● Climate change: There is a growing emphasis on limiting global warming to 1.5 °C by 2050 as called for in the Paris Agreement. Many governments and international climate panels have proposed agendas to achieve net-zero carbon dioxide emissions by 2050 as well. However, numerous industries, including the chemicals, cement, and metal industries, cannot readily avoid carbon emissions. To minimize carbon emissions from such carbon-intensive industries, it is essential to deploy some form of carbon capture and storage (CCS) (United States Department of State and the United States Executive Office of the President, 2021). Mafic and ultramafic rocks like basalts, gabbros, peridotites, and their metamorphosed equivalents (greenstones) have mineral assemblages with the potential to sequester carbon dioxide (CO2). Recent studies presented by Mineralogic (Diedrich, 2022) at the 2022 Minnesota Minerals & the Green Economy Forum reveal that the geology of the Duluth Complex and Tamarack complex is particularly amenable to carbon mineralization. However, studies by Santos et al. (2015) note that during carbon mineralization, olivine minerals – present in mafic and ultramafic rocks – convert the silicates (mainly forsterite (Mg2SiO4) and fayalite (Fe2SiO4)) into carbonates and silica. This reaction is exothermic and is, thus, thermodynamically favored. The reaction mechanism contains three main steps: the dissolution of CO2 in the aqueous solution to form carbonic acid; the dissolution of magnesium in the aqueous solution, and the precipitation of magnesium carbonate. However, Santos et al. note that dissolution of alkaline earth elements is the rate-limiting step, and as a result, the primary challenges in scaling mineral carbonization techniques are related to improving the dissolution kinetics of alkaline earth elements from silicates using a wide range of additives and varying operating conditions such as temperature, pressure, CO2 concentration, solid to liquid ratio, and particle size. Minnesota has significant amounts of these rock types, and further research to characterize their potential and applicability for carbon sequestration is necessary. The hydrometallurgical research tools identified in this research will help gather data related to: o impact of temperature, humidity, particle size, and surface area of the olivine mineral on mineral dissolution; o impact of pH, temperature and availability of cations, such as magnesium (Mg) and calcium (Ca) on the rate of carbonate mineral precipitation; and o develop maps of mafic and ultramafic rocks that include their mineral content and estimates of their potential rates of CO2 uptake through carbon mineralization. ● Electrification powered by renewables: To reduce carbon footprints, stakeholders across a range of industries have been making strides to substitute electricity for fossil fuels. Accelerated adoption of renewable energy sources, battery storage systems, electric vehicles, and electrification of heating are predicted to increase the demand for nonferrous metals like copper, nickel, manganese, cobalt, vanadium, platinum group elements, rare earth elements, lithium, and aluminum (Deloitte, 2021). However, the mining industry faces several challenges to meet this increasing demand, including but not limited to: 1) supply chain disruption brought on by the COVID-19 pandemic and geopolitical crises; 2) social expectation on ethical sourcing of metals from conflict-affected areas; 3) the steady decline in discovery rates for new ore bodies via mineral exploration; and 4) declining ore grades that are simultaneously associated with increases in waste generation, energy and water consumptions, and carbon emissions brought on by more extensive processing. To overcome these challenges, there is a strong demand for NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 23 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance technologies that can improve both water and energy efficiencies, minimize waste generation and pollution, and improve recycling rates of critical metals, as well as produce value-added materials to support a carbon-neutral economy. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 24 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part IV: Emerging Hydrometallurgical Technologies One of the primary objectives of this research was to identify current and emerging hydrometallurgical technologies with applications for processing Minnesota mineral and waste resources. Based on inputs from stakeholders, NRRI focused on gathering more information on emerging technologies that could potentially: 1. Diversify the state’s minerals economy; 2. Enable conversion of waste to value opportunities; 3. Assess carbon mineralization potential of local geological formations and waste resources; and 4. Advance technology readiness levels of emerging hydrometallurgical technologies that help protect our water resources, create new jobs, and enhance the competitiveness of the state's minerals economy. The following sections focus on emerging technologies that have been demonstrated at lab and pilot scale elsewhere and have or have not been demonstrated using Minnesota’s mineral and waste resources. (Note: the list is not exhaustive.) Hydrometallurgical technologies that are commercially practiced in the United States and rest of the world are listed in Appendix C. Note that the report does not delve into conventional hydrometallurgical technologies with limited evidence of previous application to Minnesota mineral resources. Figures 4 and 5 summarize NRRI’s research focus in hydrometallurgy and technologies with applications for processing Minnesota’s mineral and waste resources. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 25 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 4. NRRI's vision for application of hydrometallurgical technologies to Minnesota resources. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 26 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 5. Hydrometallurgical technology categories and their relevance to Minnesota resources. CESL process (Teck Resources) Platsol process (Polymet Mining) Albion process (Glencore/Talon) Chloride leach process (PRO) Battery metal extraction Critical metal extraction Waste characterization Carbon mineralization Existing commercial hydromet technologes for Cu, Ni, Ti, PGM, Mn extraction Insitu leaching Heap leaching Ammleach process Intec process Hydrocopper process Sherrit process Galvonox process Conventional Demonstrated for MN resources Limited demonstration for MN resources Emerging Emerging technologies with limited demonstration for MN Resources Emerging technologies that have been demonstrated for MN Resources Conventional technologies with limited previous application for MN resources Conventional technologies that have been practiced commercially for non-ferrous resources NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 27 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Emerging technologies with limited demonstration to Minnesota resources The technologies in this category have been demonstrated at lab- and pilot-scale elsewhere but have not been applied to Minnesota’s mineral and waste resources. As such, the relevance of these technologies to Minnesota’s mineral and waste resources includes significant research and development opportunities. The technologies in this category have been sub-categorized into four groups based on their end-use application: 1) battery metals for energy storage technologies; 2) critical metal extraction technologies; 3) carbon mineralization technologies; and 4) heavy metal capturing technologies. In some cases, hydrometallurgical technologies support the production of feedstocks or secondary materials for these emerging technologies. In other instances, the hydrometallurgical technologies enable the production of value-added material from mineral- and waste resources. An attempt has been made to identify potential applications of these technologies to Minnesota specific resources. Table 3 summarizes the feedstock requirements for these technologies and detailed descriptions of each can be found in Appendix B. A few notable examples of emerging technologies are: ● Hydro-to-Cathode™ technology converts mixed streams of waste lithium-ion batteries into various nickel manganese cobalt (NMC)-based cathode active materials, resulting in 50% reduction in cost and 93% reduction in emissions compared to the production of virgin cathodes from newly mined material (Ascend Elements, 2021). ● 100% of industrialized iron-based cathode manufacturing is currently located in China, threatening the long-term scalability of electrification in the United States. Mitra Chem, a Silicon Valley startup, aims to boost the production of iron-based cathodes for electric vehicles and stationary storage in the United States (Mitra Chem Technologies, 2021). ● The One Pot Process enables the production of cathode materials directly from nickel, manganese, and cobalt metal powders, thus eliminating the need for metal sulfate salts as a starting feedstock material. As a result, the process eliminates sulfate waste, generation of wastewater, and added shipping costs (Nano One Materials Corp., 2021a, 2021b, 2021c). ● Iron Salt Technology is designed for storage of renewable energy from wind and sun. The iron- based electrolyte is non-flammable and is mostly pure water. The low cost and abundant availability of iron-based storage media offers a potential to shape the future of energy storage beyond lithium (VoltStorage GmbH, 2021). ● Our Next Energy (ONE), a Michigan-based startup, has designed a battery pack that can extend the driving range of an electric vehicle to 750 miles on a single charge. The higher energy density of manganese-based cathodes translates into longer range, while the lithium iron phosphate cathode chemistry reduces costs and eliminates fire risks by eliminating the use of more expensive nickel and cobalt chemistry (Our Next Energy, 2021). ● Phoenix Tailings, a University of Connecticut-affiliated startup, is working to build a solution to extract critical metals from legacy tailings ponds (Small Business Innovation Research (SBIR), 2020; Severance, 2020). ● Redwood Materials, a Nevada-based startup, is creating a circular supply chain for batteries and helping partners across the electric vehicle and clean energy industries by providing pathways, processes, and technologies to recycle and remanufacture lithium-ion batteries (Redwood Materials, 2021). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 28 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance ● Nth Cycle, a Boston-based startup that has developed an electro-extraction technology to extract critical metals from batteries, e-waste, low-grade ore, and mine tailings (Nth Cycle, 2021). ● Heirloom Carbon is a San Francisco-based startup that aims to enhance carbon mineralization to help minerals absorb CO2 from the ambient air in days, rather than years. Heirloom Carbon Technologies asserts it can obtain carbon removal for $50 a ton and aims to remove one billion tons by 2035 (Temple, 2021). ● Tusaar Corp has developed a biocarbon sorbent for removal of lead, mercury, uranium, and other toxic metals from water and the environment (Tusaar Corp, 2022). ● Claros Technologies, a University of Minnesota startup, has developed a ''Clarosorb Hg" sorbent that captures toxins like mercury and PFAS. The sorbent finds application in a variety of industries, including industrial water treatment, watershed management, and air pollution control (Claros Technologies, 2022). ● Blue Planet Systems, a Silicon Valley-based start-up, has developed a geomimetic mineralization technology, which uses CO2 from any source and at any concentration as a feedstock to create carbon-negative aggregate. Blue Planet’s process uses carbon dioxide exactly as it comes out of the power plant without having to purify it (an energy and capital-intensive process) and turns it into calcium carbonate, essentially artificial limestone (Pultarova, 2019). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 29 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 3. Summary of emerging technologies and their potential applications to Minnesota resources (United Nations, 2022). Technology Group Emerging Technology Technology Function Feedstock Requirements Emerging Applications of Hydrometallurgy to Minnesota-Centric Resources Battery Materials for Energy Storage Technologies One Pot Process Production of higher performance cathode materials Pure metallic powders (e.g., Co, Mn, Ni); lithium carbonate Hydromet may allow production of high- purity nickel, cobalt, manganese metal powders from Cu-Ni-Co-PGM, Mn-Fe, Ti-V or waste batteries. Battery Grade Nickel Sulfate Production of raw materials for battery manufacturing Nickel sulfide concentrate Hydromet may allow production of battery-grade nickel sulfate powders from Cu-Ni-Co-PGM or waste battery resources. Battery Grade Manganese Sulfate Production of raw materials for battery manufacturing Manganese oxide or carbonate ores Hydromet may allow production of battery-grade manganese sulfate powders from Mn-Fe resources Direct Nickel Process Production of mixed hydroxide precipitate for the EV battery industry Nickel laterite ores Hydromet may allow production of hydroxide precipitate from potential olivine-rich Ni/Co resources. Hydro-to-Cathode Technology Transforms old batteries into advanced battery materials E-waste (Li-ion batteries) Transform old batteries into advanced battery materials using hydrometallurgical techniques Li-cycle Spoke & Hub Technology Process for recovery of critical materials from all types of lithium-ion batteries E-waste (Li-ion batteries) Li-Cycle’s hydromet technology may allow production of lithium carbonate, nickel sulfate, cobalt sulfate, and manganese carbonate from waste batteries Iron Salt Technology & Vanadium Redox Flow Technology Long duration battery for ensuring grid scale base load Vanadium-based liquid electrolyte Hydromet may allow production of vanadium- and iron-based compounds from Ti-Fe-V resources NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 30 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Technology Group Emerging Technology Technology Function Feedstock Requirements Emerging Applications of Hydrometallurgy to Minnesota-Centric Resources capability of wind and solar parks and iron-based electrolyte Iron-Based Cathode by Mitra Chem Technologies Production of iron- based cathodes for the electric vehicle and energy storage market Battery grade iron compounds (e.g., iron sulfate, iron oxide, etc.) Hydromet may allow production of iron compounds suitable for Lithium-iron- phosphate (LFP) applications Critical Metal Extraction Technologies Electro-Extraction Technology by Nth Cycle Recover critical minerals from separated e-waste, low-grade ore, and mine tailings Critical minerals from e-waste, low- grade ore, and mine tailings Nth Cycle’s electro-extraction process enables production of critical metals such as Ni, Co, Cr, Mn, Ti, Cu, and PGM Re-mining technology by Phoenix Tailings Recovery of critical raw materials used in: cell phones, automobiles, aerospace and more from old legacy tailings Mine tailings Phoenix Tailings hydromet-based technology may allow production of iron compounds, titanium, alumina, and rare earth elements Catalytic leaching technology by Jetti Resources Extract copper from low-grade primary sulfides such as chalcopyrite Copper concentrate Jetti’s process may allow recovery copper from Cu-Ni-Co-PGM resources at atmospheric temperature and pressure Mineral Carbonization Carbfix Provides a natural and permanent solution to store CO2 Geological formations containing mafic and ultramafic rocks Evaluate the in-situ CO2 sequestration potential of various rock formations in Minnesota NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 31 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Technology Group Emerging Technology Technology Function Feedstock Requirements Emerging Applications of Hydrometallurgy to Minnesota-Centric Resources Carbin Minerals Enables mines to become massive carbon sinks while producing the metals needed to drive the clean energy transition Mine tailings Evaluate the in-situ CO2 sequestration potential of various rock formations in Minnesota UBC’s CO2 mineralization and concurrent metal extraction CO2 sequestration and critical metal extraction Ca-Mg rich mafic & ultramafic rocks containing Ni-Co & PGMs UBC’s process may allow simultaneous CO2 sequestration (ex-situ) as well as Ni-Co- PGM extraction from Cu-Ni-Co-PGM resources Heavy Metal Capturing Technologies Sulfur Based Sorbents Adsorption of mercury from water Mine drain containing mercury Sulfur-based sorbents may allow mercury capture from potential discharges to mercury-impaired waters Tusaar Corp’ Biocarbon Sorbent Adsorption of mercury and other heavy metals from water Biocarbon-based sorbents may allow mercury capture from potential discharges to mercury-impaired waters Zero Valent Iron (ZVI) Technology Removal of selenium from water Waste tailings and rocks capable of releasing selenium and other heavy metals Apply zero-valent-iron to potentially capture selenium and other heavy metals from industrial discharges Advanced Biological Metals (ABMet) Technology Removal of selenium from water Biological remediation techniques may allow capture of selenium and other heavy metals from potential discharges NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 32 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Technology Group Emerging Technology Technology Function Feedstock Requirements Emerging Applications of Hydrometallurgy to Minnesota-Centric Resources Saturated Rock Fill (SRF) Technology Removal of selenium from water Apply SRF technology to prevent oxidative dissolution of pyrite that leads to release of Se and nitrate ions into water NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 33 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part V: Strategic Fit of Emerging Technologies to NRRI Core Competencies NRRI is an applied research organization whose mission is to deliver integrated research solutions that value our resources, environment, and economy for a sustainable and resilient future. NRRI’s research informs decisions on natural resource utilization and drives economic opportunities for the State of Minnesota and beyond. The economy of the future will be defined by the natural resource nexus of water, energy and materials within the sustainable development nexus of the environment, economy and society. Several challenges were noted from the VOC stakeholder engagement survey, including: ● Timeliness of environmental review and permitting process ● Need for advanced processing and environmental characterization laboratory ● Need for value-added products ● Complementary techniques to hydrometallurgical techniques ● Diversification of minerals economy ● Protecting water resources and mitigating mine drainage ● Reuse and recycling of critical metals ● Mercury impaired waters ● Climate change ● Minerals required to support clean energy technologies Table 4 describes the alignment of NRRI’s mission and core competencies with stakeholder needs and Figure 6 plots those needs against NRRI’s core competencies. Permitting timelines for new development projects is a concern for stakeholders, but because NRRI is not a regulatory agency, this topic is outside the scope of work for NRRI. However, NRRI could potentially supply experimental data to support the environmental impact assessments of emerging hydrometallurgical technologies. Similarly, the safety of tailings storage facilities is a concern for stakeholders; NRRI’s current research competencies do not focus on geotechnical stability of tailings dams. Based on surveys, five key stakeholder needs aligned with NRRI’s core competencies. These were: 1) feasibility of battery metal extraction for renewable energy storage systems from Minnesota’s mineral and waste resources; 2) defining beneficiation characteristics for regional critical mineral resources; 3) potential mine drainage assessment from potential waste resources via accelerated aging; 4) characterization of mineral formations and waste tailings for permanent sequestration of CO2; and 5) mercury removal treatment technologies. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 34 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 6. Relevance of stakeholder issues to NRRI's core competencies. Mine drainage assessmentTailings dam safety Permitting timeline Battery metal productionCO2 mitigation strategy R&D laboratoryCritical minerals extraction Diversification of minerals economyReuse and recycling Alignment to NRRI's Core Competencies Import ance to Stakeh olders NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 35 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 4. Alignment of stakeholder needs to NRRI's core competencies. Stakeholder Needs Emerging New Technologies NRRI Mission Alignment Research Relevance to Minnesota Battery metal extraction and long- duration energy storage technologies 1. One Pot Process (Nano One) 2. Iron Salt Technology & Vanadium Redox Flow Technology (Volt Storage) 3. Direct Nickel Process (Altilium Group, 2021) 4. Catalytic leaching technology (Jetti resources) 5. Hydro-to-Cathode Technology (Ascend Elements) 6. Iron-Based Cathode (Mitra Chem Technologies) 1. Implement new processes and introduce new products derived from Minnesota ores and waste resources 2. Energy and storage siting in Minnesota 3. Diversify Minnesota’s mineral portfolio 4. Maximize the value of mined materials while minimizing the risk 1. Implement new processes and introduce battery materials from Minnesota’s copper, nickel, iron, manganese, titanium and vanadium resources 2. Support the development and commercialization of mineral projects by collaborating with other public and private entities to create a climate where private investment is encouraged and new technology and process innovation is supported Critical metal extraction technologies 1. Phoenix Tailings-Re-mining technology 2. Lilac Solutions Ion-Exchange Technology 3. Nth Cycle Electro-Extraction Technology 4. Li-Cycle Spoke & Hub Hydrometallurgical Technology 1. Resource conservation and innovative utilization 2. Identify, quantify, and characterize mineral-based secondary products 3. Pursue value-added product development and technology opportunities 1. Implement new processes and introduce high-value-added materials from Minnesota’s e-waste, low-grade ores, and mine tailings 2. Encourage deployment of new technologies in rural Minnesota that add value to Minnesota’s minerals Heavy-metal-capturing technologies 1. Sulfur-based sorbents 2. Nano selenium sponges (Claros Technologies) 3. Biocarbon sorbent (Tusaar Corp) 4. Zero Valent Iron (ZVI) 5. Advanced Biological Metals (ABMet) 6. Saturated Rock Fill (SRF) 1. Promotes water quality and equity 2. Remediation strategies to improve degraded ecosystems 3. Allows management of water resources in a sustainable way that allows for efficient use of the resources by humans and wildlife 1. Supports First Nations and Indigenous heritage protection 2. Helps future industries to gain social license to operate with Indigenous communities 3. Facilitates delisting of 27% of the total inventory of mercury-impaired waters in Minnesota (Minnesota Pollution Control Agency, 2022) 4. Helps achieve Fond du Lac Band’s human health chronic standard of NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 36 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Stakeholder Needs Emerging New Technologies NRRI Mission Alignment Research Relevance to Minnesota 0.77 ng/L mercury from potential mine/municipal discharges (Fong, 2022) 5. Helps demonstrate new control technologies for containing and treating acid mine drainage that can be associated with mining Mineral carbonization technologies 1. Carbfix Technology 2. Carbin Minerals 3. Direct Air Capture via Enhanced Weathering (DACEW) 1. Promotes decarbonization strategies 2. Carbon capture and storage siting in Minnesota 3. Utilizes Minnesota’s inventory of carbon-reactive minerals to capture CO2 4. Support for demonstration projects of new technical developments that show good promise for enhancing the competitiveness of Minnesota mines 1. Understand the spatial distribution of Mesoproterozoic Duluth Complex rocks (OUIs) and how that relates to CO2 storage 2. Characterize the carbon storage capacity of waste mineral resources in Minnesota via ex-situ carbon mineralization 3. Understand challenges specific to scaling carbon mineralization technologies in Minnesota 4. Evaluate the chemistry and carbon reactivity of different rock types, the porosity and permeability of the potential reservoir, and its pressure and temperature state during CO2 injection and mineralization 5. Evaluation of the potential effect of geochemical contamination from in- situ carbon mineralization 6. Evaluate the impact of carbon mineralization on terrestrial, coastal, and Lacustrine environments NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 37 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part VI: Research Priorities for NRRI Based on the VOC survey, funding availability for each opportunity, and alignment with NRRI core competencies, five key research opportunities were identified. The proposed research emphasizes creating solutions to help utilize Minnesota’s mineral- and waste resources in a manner consistent with the United Nations’ definition of “sustainability” (United Nations, 2022). ● Defining Beneficiation Technologies for the Production of Battery-Grade Materials from Minnesota’s Mineral and Waste Resources In Minnesota, Cu-Ni±PGE and Ni-Cu±PGE mineralization is associated with the Duluth Complex and the Tamarack Intrusive Complex, respectively. Historical recovery studies have investigated three different processing routes for nickel extraction from these resources, including: 1) flotation concentration that produces smelter grade nickel concentrates; 2) hydrometallurgical processing that includes pressure oxidation leaching (PLATSOL™ and CESL) to process nickel concentrates into upgraded nickel-cobalt hydroxide products; and 3) hydrometallurgical processing that includes atmospheric oxidative leaching (ALBION Process™ and Mixed-Chloride Technology) to solubilize nickel from nickel concentrates. These leaching and related impurity removal techniques are not optimized for battery-grade nickel production, and instead result in intermediate nickel products. With accelerated adoption of electric vehicles (EVs), Deloitte forecasts a 10-to-20-fold increase in demand for battery-grade nickel by 2030, which could potentially intensify if nickel becomes a critical catalyst in the hydrogen economy (Deloitte, 2021). Further research is necessary to upgrade regional mineral and waste resources to battery-grade products like nickel sulfate (see Table 8 for product specification), high-purity manganese sulfate monohydrate, and lithium titanium oxide. NRRI may explore emerging hydrometallurgical technologies that allow production of battery grade metals required for the production of cathode active materials from regional virgin ores, intermediate mixed hydroxide precipitates (MHP), and waste scrap materials, while understanding the impacts on water consumption, waste generation, and production costs. Appendix A shows how analytical tools like ICP-MS and research process equipment like Armfield Reactors, Applikon Dependable Instruments Benchtop Reactor, and Büchi AG miniPilot Reactor can be used in these research efforts. ● Waste Rock Characterization Via Accelerated Aging Historically, humidity cell tests are used to: 1) simulate geochemical weathering (natural oxidation) processes; 2) determine the rate of acid generation and variation over time in leachate water quality; 3) provide a preliminary assessment of acid rock drainage (ARD) control options; and 4) evaluate potential solid materials generated by the weathering process (ASTM International, 2018). Humidity cell tests often last from weeks to years and typically require data collection on a seven-day cycle; as a result, they usually involve significant time and expense. Moreover, determination of acid drainage potential from a humidity cell test is often inconclusive due to failure to deplete neutralization potential to levels at which acid generation becomes measurable (U.S. Environmental Protection Agency (EPA), 1994). NRRI may consider conducting experiments utilizing a pressurized reactor to evaluate accelerated aging, which may allow collection of relevant humidity cell data over a shorter period. ● Mapping Domestic Critical Mineral Resources and Defining Beneficiation Technologies Minnesota contains a variety of critical minerals resources including cobalt, manganese, platinum group elements, titanium, and vanadium. Current NRRI research associated with the US Geological Survey Earth Mapping Resources Initiative program (Earth MRI) will improve our understanding of critical mineral resource potential within the state (United States Geological NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 38 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Survey, 2021). NRRI has identified advanced processing tools that may be suitable for critical mineral processing within Minnesota, including the Magotteaux Mill, Attritor Mill, Computerized Laboratory Flotation Cell, Ore Sorting, Reflux Classifier, which will help assess the beneficiation characteristics of critical mineral resources, and the Parr Bench-Top Autoclave Reactor, Armfield Reactors, Applikon Dependable Instruments Benchtop Reactor, and Büchi AG miniPilot Reactor, which will support investigations that assess amenability of ore samples to hydrometallurgical processing. ● Characterization of Mineral Formations and Waste Tailings for Permanent Sequestration of CO2 The Intergovernmental Panel on Climate Change (IPCC) suggests removing large volumes of CO2 from the atmosphere to achieve the climate goals in the Paris Agreement (United States Department of State and the United States Executive Office of the President, 2021). One approach for atmospheric CO2 removal is carbon mineralization, in which certain rock types containing calcium, magnesium or other elements bind with CO2 to form carbonate minerals. Examples of rock types that contain calcium or other elements that bind CO2 include ultramafic or mafic igneous rocks (Sandalow, et al., 2021), such as peridotite, gabbro, basalt, and their metamorphosed equivalents (greenstones), which are found throughout Minnesota and contain minerals such as olivine, pyroxene, plagioclase, zeolites, etc. However, a deeper understanding of the carbon mineralization process is required to practice at large scale (U.S. Department of State, 2021) and hydrometallurgy will play a key role in generating secondary products used in carbon mineralization process. In conjunction to CO2 sequestration, hydrometallurgical processes may enable the extraction of energy-relevant minerals like nickel, cobalt, manganese, and vanadium from mafic and ultramafic rock (Wicks, 2022). Appendix A shows how process research tools like Applikon Dependable Instruments Benchtop Reactor, Büchi AG miniPilot Reactor, and Parr bench-top autoclave reactors support carbon mineralization and critical mineral extraction research. ● Explore Treatment Technologies to Reduce Mercury Concentration to 0.77 ng/L (the Fond du Lac Band standard) In-stream mercury concentrations in the St. Louis River, measured by the Fond du Lac Band, have been below the Great Lakes Initiative (GLC) Chronic Wildlife Standard of 1.3 ng/L but exceed the Fond du Lac Band’s human health chronic standard of 0.77 ng/L. For this reason, the Fond du Lac Band is concerned about any new or expanded discharges to the St. Louis River upstream of the Fond du Lac Indian Reservation that could adversely affect mercury bioaccumulation in fish. Bioaccumulation of mercury in aquatic organisms is a concern to tribal authorities, as many tribes rely on fish for subsistence and cultural practices. NRRI will review the existing scientific literature for treatment technologies capable of achieving a mercury concentration of 0.77 ng/L from industrial waste discharges. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 39 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part VII: Conceptual Design of a Hydrometallurgical Research Laboratory Summary of Intent The purpose of the conceptual design is to provide a foundational understanding of key laboratory tools required to support the development of emerging hydrometallurgical technologies with applications to Minnesota mineral and waste resources. As discussed in the previous section, bench-scale testing is a prerequisite to a pilot-scale program; therefore, the current effort is to devise a strategy to identify bench-scale and semi-pilot simulators to support and sustain a hydrometallurgical research facility. Because each pilot plant operation has distinct objectives, feedstocks, unit operations, scale, lifespan, operational conditions, and materials of construction, there is no “one size fits all” pilot or demonstration solution. Therefore, NRRI will focus on conducting research on bench-scale and semi- pilot scale, which requires significantly less capital expense and fewer permitting requirements. In the event a need arises for a hydrometallurgical pilot or demonstration plant to support the development and commercialization of novel technologies, NRRI may collaborate with engineering companies or commercial laboratories (example labs are listed in Tables 7 and 8). Hydrometallurgical Process Development Metallurgical studies are necessary during all stages of mineral resource development beyond exploration and discovery. They provide the basis and justification for process and equipment design as well as for waste handling systems, resource estimation, environmental impacts, reclamation strategies, permitting requirements, marketability of products, and economic evaluation of proposed projects. Metallurgical studies can be carried out from bench- and pilot-scales through demonstration plants, and while progression from bench- to demonstration-scale increases complexity, timelines, and expense, it also reduces the risk associated with commercial development (McNulty, 2002). A brief overview of these testing scales and their objectives are given below. Bench-Scale Testing Bench-scale tests are carried out on representative samples of the anticipated feed in beakers, flasks, and small-scale simulators like batch flotation cells, leaching tanks, autoclaves, etc. These tests are carried out under well-defined chemical and physical conditions to provide reliable information about underlying principles. Ideally, bench-scale tests will determine the probable process flowsheet, physical and chemical operating conditions, anticipated product quality, and material balance for the design of the pilot plant (McNulty, 2002). Pilot-Scale Testing Pilot tests are performed on larger samples (few hundred kilograms to a ton) in small-scale prototypes operating intermittently or continuously, with the primary goal of confirming the results of bench-scale observations. Additional objectives could include: 1) a study of the impacts of recycled streams on final product quality; 2) production of large samples for further treatment like smelting or byproduct recovery; 3) determining the marketability of products to potential customers; 4) training plant operators; 5) generating information needed for regulators; and 6) proof of concept to help obtain financing. Pilot-scale confirmation of bench-scale results enables well-informed selection of processing unit operations, equipment size, materials of construction, and general arrangement for commercial plant layouts (McNulty, 2002). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 40 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Demonstration Plants Demonstration plants are fully integrated collections of semi-commercial unit operations that can be used to operate successive unit processes. Feed rates for demonstration-scale plants range from a few kilograms to several tons per hour, and their primary purpose is to reduce risk of project development for novel technologies through the identification of process risks that are typically not observed in pilot plants or in short-duration campaigns (McNulty, 2002). Laboratory Prototypes and Simulators The following section identifies laboratory equipment needed to address stakeholder needs identified in the VOC survey, including extracting critical metals and battery grade materials from mineral and waste resources, assessing the potential for carbon mineralization, and investigating impacts of waste rocks and other waste resources on water quality, including mine water remediation. Battery Metal Production, Critical Metal Extraction, and Carbon Mineralization ● Advanced mineral processing tools for beneficiation of ores from Cu-Ni-Co-PGE and Ti-V deposits, Fe and Mn-Fe deposits, and aggregate and byproduct resources like mine tailings, industrial residues, and electronic waste. ● Metal dissolution and CO2 sequestration tools to evaluate amenability of samples for conventional or novel leaching technologies and carbon mineralization potential of CO2 reactive minerals and rocks. ● Solution purification tools to allow separation and purification of leach liquors using solvent extraction, ion exchange, adsorption techniques. ● Metal recovery tools to produce high-purity metal compounds using precipitation and electrowinning techniques. Waste Rock Characterization ● Pressurized batch reactors for accelerated aging to investigate leachate quality and dissolved metal flux from potential oxidation of waste rock, electronic waste, and/or mine tailings. Mine Water Remediation ● Column chromatography and column leach reactors to capture mercury and other heavy metals using novel sorbents. Hydrometallurgical Research Equipment Table 5 lists strategic equipment identified in the VOC survey and categorized based on scale, process, function, and application. Table 6 provides a high-level budgetary capital estimates for some of the critical laboratory equipment. Note the cost does not include building, installation, and commissioning costs. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 41 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 5. Laboratory equipment required to support a hydrometallurgical research facility. Laboratory Equipment Scale Category Function Potential Application FRITSCH Mortar Grinder PULVERISETTE 2 Lab Milling Used for wet and dry grinding, mixing, and homogenization. The mill allows cryogenic grinding at lab-scale. Suitable for grinding hard, medium-hard, soft, brittle, fibrous and abrasive materials prior to leaching Magotteaux Mill™ Lab Milling Simulate the pulp chemical conditions of the plant grinding mill in the laboratory Investigate the impact of grinding chemistry on extraction processes such as flotation and leaching Union Process Attritor Mill (vertical ball mill) Lab Milling Lab scale wet or dry grinding Allows grinding under inert atmospheres, operates at controlled temperatures, overcomes product contamination, and allows estimation of precise grinding energy consumption Laboratory Hydrocyclone Rig Mini-pilot Classifier Particle classification Prepare ground slurries for downstream metallurgical processes like flotation and leaching Mozley Superpanner Bench Gravity Separator Separates mineral grains of close specific gravity at a laboratory scale Allows gravity separation of ilmenite, manganese iron ores, PGE minerals, and CO2 reactive rocks FLSmidth Reflux Classifier Mini-pilot Gravity Separator Separates fine particles based on a difference in density or particle size Investigate amenability of ilmenite ores, manganese iron ores, PGE minerals, CO2 reactive rocks to gravity separation Magotteaux Float Cell™ Bench Flotation Separator Bottom-driven float cell that allows continuous pulp chemistry monitoring Investigate amenability of ilmenite ores, manganese iron ores, PGE minerals, CO2 reactive rocks to flotation separation NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 42 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Laboratory Equipment Scale Category Function Potential Application LAARMANN Computerized Laboratory Flotation Cell (fully computerized) Bench Flotation Separator Digitally controlled flotation cell ideally suited in duplicating plant processes and operations Cells and impellers are designed to handle corrosive flotation conditions Glencore L150 Laboratory Jameson Cell Mini-pilot Flotation Separator Enables ultrafine particle flotation Suitable for sulfide, non-sulfide and industrial minerals flotation TOMRA Ore Sorting Mini-pilot Sorter Sensors separate valuable mineral ores from waste rocks based on their color, atomic density, transparency or conductivity Sensor-based ore sorting systems allows dry material separation of various ores and industrial waste materials Bottle Roller Bench Leach Reactor Simulate atmospheric leaching at lab scale Investigate amenability of ilmenite, manganese iron ores, Cu-Ni-PGE minerals, CO2 reactive rocks to atmospheric leaching Armfield Reactors (fully computerized) Bench Leach and Precipitation Reactor Simulates continuous stirred tank reactor, tubular reactor, batch reactor, laminar flow reactor, and plug flow reactor in lab-scale Investigate the effect of varying the temperature, mixing speed, feed rate, etc. on reaction rate; allows determination of the residence time using tracer techniques; allows evaluation of empirical rate expressions from experimental data NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 43 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Laboratory Equipment Scale Category Function Potential Application Applikon Dependable Instruments Benchtop Reactor Bench Leach and Precipitation Reactor Simulation of atmospheric leaching (mixed chloride, Albion, bacterial leaching process) and metal precipitation on a bench scale Suitable for producing leach liquors from ilmenite ores, manganese iron ores, Cu- Ni-PGE minerals, and CO2 reactive rocks for downstream metal extraction processes; suitable to study precipitation of metals from leach liquors Chem Glass Jacketed Lab Reactor Mini-pilot Leach and Precipitation Reactor Allows chemical process development, scale-up, process simulation and kilo- scale production Suitable to produce large batches of leach liquors; allows simulation of precipitation and crystallization processes Parr Bench-Top Autoclave Reactor Bench Pressure Reactor Simulation of pressure oxidative leaching processes such as Platsol and CESL in lab scale Investigate amenability of ilmenite ores, manganese iron ores, Cu-Ni-PGE minerals, CO2 reactive rocks to pressure oxidative leaching Column Leach Reactor Mini-pilot Plug Flow Leach Reactor Simulation of bacterial heap leaching; simulation of sorbent adsorption The reactor is suitable to study bacterial leaching of Cu-Ni-PGE minerals. Also, suitable to screen sorbents for contaminant extraction from wastewater Bench Scale Leach Pilot Plant Bench Leaching Reactor Simulation of atmospheric leaching on a continuous bench and mini-pilot mode Suitable for low-volume low-flow continuous integrated bench and min- pilot plant extraction of metals via leaching Parr Multiple Pressure Reactor System Bench Pressure Reactor Simulation of accelerated aging at high temperature, high pressure, and with various gas compositions Suitable to evaluate leachate quality from accelerated aging of waste rocks NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 44 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Laboratory Equipment Scale Category Function Potential Application Filter Press Bench Solid-Liquid Separator Separate insoluble solids from leach liquors Allows to separate leach liquors from solid residues for solvent extraction, ion exchange, and precipitation experiments Thermo Scientific Benchtop Orbital Shakers Eppendorf ThermoMixer Gerhardt Thermoshake Incubator Shaker Burrell Scientific Variable Speed Wrist Action® Shaker Bench Liquid-Liquid Separator Screen various organic extractants. determine reaction time, temperature, extractant concentration, salt concentration, pH, determine the number of stages and optimal aqueous- to-organic phase ratio of extraction, scrubbing and stripping based on McCabe-Thiele diagrams Allows development of a solvent extraction process to selectively separate targeted metals ions from leach liquors Rousselet Robatel Mixer Settler Bench Liquid-Liquid Separator Simulation of solvent extraction on a continuous counter current mode Examine the possibility of scaling up the solvent extraction process and/or producing larger volumes of purified metal solution Bench Scale Electrowinning Pilot Plant Bench Electrochemical Reactor Simulate electrowinning on a bench scale Allows electrowinning copper, cobalt, nickel, gold, chromium, zinc and other metals Column Chromatography Bench Ion Exchange/ Adsorption Simulate ion exchange and adsorption processes in a lab scale Allows the design of a metal-separation process using ion-exchange resins and various other adsorbents, which are mostly suitable for the selective extraction of various diluted streams and solutions NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 45 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 6. Summary of budgetary estimate required to support hydrometallurgical research. Component Budgetary Estimate (as of June 2022) Laboratory and Semi-Pilot and Analytical Equipment $600,000 to $1.2 million Installation and Facilities Support $100,000-$200,000 Personnel $200,000 to $300,000 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 46 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part VIII: Benchmarking North American Hydrometallurgical Research Facilities This section summarizes the capabilities of some of the leading research laboratories in North America. Table 7 shows a list of some of the North American laboratories with hydrometallurgical capabilities. Table 8 summarizes a list of key research and analytical equipment of these institutions. (Note: The list is not exhaustive and does not cover some of the commercial laboratories). Table 7. A comprehensive list of institutes and laboratories with hydrometallurgical research capabilities in North America. Laboratory Name Type Location ALS Global Commercial BC, Canada COREM Commercial Quebec City, Canada Hazen Research, Inc. Commercial Golden, Colorado Kemetco Research Inc. Commercial BC, Canada Kingston Process Metallurgy Inc. Commercial Ontario, Canada Metals U.S/Intellimet Commercial Montana, USA McClelland Laboratories Commercial Nevada, USA Met-Solve Laboratories Inc. (Sepro-Laboratories) Commercial BC, Canada Process Research ORTECH (PRO) Commercial Ontario, Canada SGS Lakefield Commercial Ontario, Canada Saskatchewan Research Council State-owned Saskatchewan, Canada XPS Expert Process Solutions Commercial Ontario, Canada Ames National Laboratory Federal Iowa, USA Argonne National Laboratory Federal Illinois, USA Idaho National Laboratory Federal Idaho, USA Oak Ridge National Laboratory Federal Tennessee, USA Colorado School of Mines University Colorado, USA McGill University University Montreal, Canada Missouri University of Science And Technology University Missouri, USA Montana Technological University University Montana, USA Penn State University University Pennsylvania, USA Queens' University University Ontario, Canada University of Alaska University Alaska, USA University of British Columbia University BC, Canada University of Kentucky University Kentucky, USA University of Nevada Reno University Nevada, USA University of Toronto University Toronto, Canada University of Utah University Utah, USA Virginia Tech University Virginia, USA Worchester Polytechnic Institute University New York, USA NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 47 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 8. Comparison of research capabilities of leading North American research institutes. Laboratory Facility Research Capabilities Analytical Capabilities Hazen Research, Inc., Colorado, USA Atmospheric and Pressure Leaching, Pressure Oxidation, Crystallization, Precipitation Solvent Extraction, Ion Exchange, Electrochemistry, Solid/Liquid Separation, Rheometry/Viscometry, Roasting, Calcining, Fluid-Bed Reactors, Rotary Kilns, Induction Furnaces, Multiple-Hearth Furnace X-ray diffraction (XRD), QEMSCAN, Electron microprobe analysis, High-resolution SEM and microanalysis, ICP–OES, ICP–MS, XRF, Flame, Cold Vapor, and Hydride AA, LECO, Wet Chemistry Methods, Ion Chromatography, Fuels Analysis Colorado School of Mines, Colorado, USA Leaching Systems, Precipitation Systems Sol Gel Processing, Molten Salt Electrorefining, Molten Salt Electrowinning, Molten Salt Heat Treatment Baths, High Temperature Melting Furnace, Vacuum Furnace (2200 °C) Extrel ELQ - 400 Triple Quadruple Mass Spectrometer, Extrel ELQ - 400 LC/MS Triple Quadruple Mass Spectrometer, Perkin Elmer Q-Mass 910 GC/MS Systems, JEOL M Station High Resolution Mass Spectrometer, Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy Fluorescence Spectroscopy, Leco Interstitial Analyzers, Scanning and transmission electron microscopy (SEM/TEM/STEM), energy dispersive spectroscopy of X-rays (EDS), electron backscatter diffraction (EBSD), focused ion beam (FIB), X-ray diffraction (XRD), atomic force microscopy (AFM), and laser/Raman confocal microscopy. Montana Technological University, Montana, USA Leach Reactors, Solvent Extraction/Ion Exchange, Electrometallurgy, Crystallization, Gaseous Precipitation, Cementation LEO Scanning Electron Microscope (SEM) w/ Energy Dispersive X-ray Spectroscopy (EDS), Automated Mineralogy using Mineral Liberation Analysis (MLA), TESCAN MIRA 3 - Field Emission Scanning Electron Microscope (FE-SEM), Cathodoluminescence (CL), Energy Dispersive X-ray Spectroscopy (EDS), Wavelength Dispersive X-ray Spectroscopy (WDS), Electron Backscatter Diffraction (EBSD), Automated mineralogy with TIMA-X Rigaku Ultima IV X-ray Diffractometer w/ thermal stage up to 1500 °C, Bruker S2 X-ray Fluorescence Spectrometer, Thermo Electron Duo View iCAP 6500 ICP-OES, NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 48 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Laboratory Facility Research Capabilities Analytical Capabilities University of Alaska, Mineral Industry Research Laboratory (MIRL), Alaska, USA Laboratory leaching, precipitation and solvent extraction equipment ICP/DCP, AA, XRD XRF, Electron Microprobe Analyzer (EPMA), and electron microscopes University of Toronto, Ontario, Canada Parr Instrument Autoclaves (2-L size); Glass Leaching Reactors (6 reactors); Auto lab Potentiostat/Galvanostat PGSTAT101 with NOVA software, Faraday Cage and RDE accessories; Bottle roll test set up for cyanidation; pH, ORP, DO and ion analyzers and controllers Agilent Technologies Microwave Plasma Atomic Emission Spectrometry (MP-AES 4200) multi-element analyzer; Two Atomic Absorption Spectroscopy Machines; 916 Ti-Touch Titrator with silver electrode for Free Cyanide titration; STA 449 F3 Jupiter – Simultaneous Thermal Analyzer TGA DSC from Netzsch; Thermo Scientific Genesys 10S UV-Vis; ELTRA CS2000 Carbon and Sulfur Determinator; OXFORD Instruments X- Supreme X-ray fluorescence (XRF) machine, Laser Particle Size Analyzer McGill University, Montreal, Canada Study of the associated solution chemistry (complexation, solubilities and activities both via experimentation and chemical modeling), determination of precipitation/crystallization kinetics in batch and/or continuous reactor set- ups, or electrochemical deposition SEM, TEM, XRD, FTIR, Raman, BET, TGA XPS; Perkin Elmer Atomic Absorption Spectrometer 311. Highly sensitive instrument (ppm level); Varian AA 240 FS Atomic Absorption Spectrometer; Horiba Laser Scattering Particle Size Analyzer; Philips PW 1710 Powder X-Ray Diffractometer; Bruker D8 Discovery X-Ray Diffractometer; X-Ray Photoelectron Spectroscopy (XPS): Thermo Scientific K-Alpha. Kingston Process Metallurgy Inc., Ontario, Canada Molybdenum disilicide tube furnaces (1700 °C), SiC tube furnaces (1400 °C), Resistance element furnaces (1200 °C), Induction furnace (10 kW), Mini-kiln and rotary furnaces, Fluid bed reactors (batch or continuous, as well as two stage), Controlled atmosphere molten salt electrolysis, Potentiostat for electrochemical studies, Denver flotation cell, Bench scale autoclaves, In-line HCl and Cl2, Gas scrubber facility ICP-OES. Atomic absorption spectroscopy (AA), Custom large scale (<10 g) thermogravimetric analyzer (TGA), Variety of magnetic separators, Infrared spectroscopy/gas chromatography, Portable 300 AMU mass spectrometer, Surface profilometers, Optical microscopy/image analysis, Scanning electron microscopy, Custom differential thermal analysis (TDA), Karl-Fisher water analysis NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 49 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Laboratory Facility Research Capabilities Analytical Capabilities Kemetco Research, British Columbia, Canada Leaching studies, Heap leach studies, Pressure oxidation, Roasting/reductive roasting, Bioleaching Solid-liquid separation, Precipitation and dissolution studies, Solvent extraction, Ion exchange, NF, RO, UF studies, Electrowinning Total metals (ICP), Gold and silver, Mercury analysis, Iron speciation, Nitrogen speciation, Phosphorus speciation, Liquid chlorine analysis, Chloride, chlorate Bromine, bromide, Fluoride Iodine, Sulfur and thiosalts speciation, Cyanide speciation, TRS gas analysis, Xanthate analysis, Alkalinity, acidity, Oxidizer classification, Resin and fatty acids, Comprehensive water/wastewater characterization Process Research ORTECH, Ontario, Canada Pilot continuous atmospheric leaching system; Bench scale titanium and pilot scale stainless steel autoclaves for high pressure leaching with capacity of up to 50 gallons; Solvent extraction system consisting of mixer settlers; pulse column and fixed bed and continuous ion exchange systems; Lab and pilot scale liquid/solid separation equipped with thickeners and filters; Electrowinning cells for product recovery ThermoScientific ICAP 6000 Series ICP Spectrometer; Perkin Elmer Instruments AAnalyst 100 Atomic Absorbance Spectrometer; ThermoScientific Niton FXL FM-XRF Analyzer; ELTRA CS 2000 Carbon Sulfur Determinator Saskatchewan Research Council (SRC), Saskatchewan, Canada Acid-roasting, Caustic cracking, Leaching, Solvent extraction, Fractional precipitation, Effluent treatment Electron microprobe, X-ray fluorescence (XRF), ICP-OES and ICP-MS Analysis NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 50 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part IX: Skill Sets Required to Sustain Hydrometallurgical Research The following skill sets are essential to develop and execute a hydrometallurgical research program at NRRI. Aqueous Research Chemist/Metallurgist This position generally requires: ● Background experience in hydrometallurgy, mineral processing, and wastewater treatment processes including flowsheet, development, bench-scale test work and pilot plant programs ● Advanced understanding of metallurgical engineering fundamentals, including heat transfer, mass transfer, fluid mechanics, chemical kinetics, thermodynamic analysis, mass and energy balance, unit operation design ● Experience in designing and developing novel chemistries and extractive metallurgical approaches in aqueous or solvent-based systems ● Experience designing and performing experiments to evaluate the feasibility and performance of new chemistries and separation technologies, including but not limited to, leaching, solid-liquid separation, water treatment and reclamation, filtration, ion exchange resins ● Experience developing and running thermodynamic and kinetic calculations and models ● The abilities to analyze experimental data and communicate results to the R&D team ● The ability to develop and implement chemical processes at the lab scale and support knowledge transfer to process engineers for system scale-up Research Technician This position generally requires: ● A basic understanding of laboratory instrumentation ● The ability to perform hydrometallurgical and advanced mineral processing sampling duties and test work procedures such as flotation, comminution, sizing, leaching, precipitation, solvent extraction, column chromatography and filtration ● Skills to prepare working stock, calibration, and reagent solutions as directed ● The ability to ensure research equipment functionality and provide assurance of calibration of the instruments ● The skills to operate general hydrometallurgical laboratory equipment ● Experience and abilities to perform routine maintenance on existing research instruments ● Skills to coordinate and execute test work as instructed by research metallurgists ● The ability to maintain accurate records of experiments, reagents, amounts of charges, and observations during experiments ● Skills for obtaining, preparing, and submitting samples for assay ● Knowledge and use of chemical handling and safe laboratory practices with the ability to adhere to SHE policies NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 51 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Analytical Chemist This position generally requires: ● A proficient knowledge of laboratory and quality systems ● An understanding of and the ability to apply basic analytical chemistry principles ● Skills necessary to develop and validate analytical methods, Standard Operating Procedures (SOPs) and other operating, safety, and quality documents for method development, transfer, and validation studies ● The ability to analyze data, run statistical analysis, and present findings to both technical and non-technical audiences ● The ability to perform routine operation, maintenance, calibration of analytical instruments ● Skills necessary to prepare standards and reagents as required and documents work appropriately ● Skills necessary to prepare samples for analysis ● The ability to perform sample analysis and interpret analysis data obtained from a variety of samples via ICP MS, ICP OES, AAS, IC, and XRF methods ● Skills necessary to perform analytical work related to quality assurance and sample analysis during test campaigns NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 52 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part X: Collaborators and Potential Funding Opportunities NRRI’s hydrometallurgical research seeks to develop relationship and collaboration with all parties involved in the minerals economy: • Regional Partners: Iron Range Resources & Rehabilitation (IRRRB), Minnesota Geological Survey (MGS), Minnesota Pollution Control Agency (MPCA), Minnesota Department of Natural Resources (MNDNR), Minnesota Department of Transportation (MNDOT) • NRRI seeks to develop relationship with Minnesota Native American/First Nations communities: Bois Forte Band of Chippewa, Fond Du Lac Reservation, Grand Portage Band of Lake Superior Chippewa, Leech Lake Band of Ojibwe, Lower Sioux Indian Community, Mille Lacs Band of Ojibwe, Prairie Island Indian Community, Red Lake Band of Chippewa Indians, Shakopee Mdewakanton Sioux (Dakota) Community, Upper Sioux Community, and White Earth Reservation. • Federal Partners: U.S. Department of Interior’s Bureau of Indian Affairs (BIA), Minnesota Chippewa Tribal Agencies, United States Forest Service (USFS), Bureau of Land Management (BLM), National Science Foundation (NSF), United States Geological Survey (USGS), U.S. Environmental Protection Agency (U.S. EPA), U.S. Department of Energy (U.S. DOE), U.S Army Corps of Engineers (USACE), US Department of Defense (U.S. DOD), Small Business Innovation Research (SBIR), Small Research Technology Transfer (STTR) • Private Entities: Mineral Resource Companies, Battery Manufacturers, Climate Tech Companies, Energy Companies, Engineering/Environmental Consulting Firms • Venture Capitalist Firms: SOSV, Lower Carbon Capital, Andreessen Horowitz, Prelude Ventures, Khosla Ventures, Total Energies, Energy Impact Partners, High-Tech Gründerfonds, Battery, Mercia, New Venture Associates, Wellington, General Catalyst, Kleiner Perkins, Alumni Ventures, Union Square Ventures, Clean Energy Ventures, Grey Croft, GV, Mayfield, Accel, Founders Fund, Imagine H2O • Private Foundations: The Wells Fargo Foundation, The McKnight Foundation, The Saint Paul Foundation, The Minneapolis Foundation, Otto Bremer Trust, United Health Foundation, Medtronic Communities Foundation, The Bush Foundation, U.S. Bancorp Foundation, General Mills Foundation, Fred C. and Katherine B. Andersen Foundation, Minnesota Community Foundation, 3M Foundation, Northwest Area Foundation, The Hormel Foundation, The Blandin Foundation, Carl and Eloise Pohlad Family Foundation, Target Foundation, Central Minnesota Community Foundation, Best Buy Foundation, Curtis L. Carlson Family Foundation, Land O'Lakes Foundation, F. R. Bigelow Foundation, The Cargill Foundation, The Xcel Energy Foundation, Andreas Foundation, The St. Paul Travelers Foundation, Ecolab Foundation, Northland Foundation, Patrick and Aimee Butler Family Foundation, CHS Foundation, RBC Foundation, George Family Foundation, I.A. O'Shaughnessy Foundation, Blue Cross and Blue Shield of Minnesota Foundation, Initiative Foundation, J.A. Wedum Foundation, Grantham Foundation. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 53 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Part XI: Summary and Recommendations The commercial development of new mineral and waste resources requires mineral exploration, mineral characterization, mineral processing development, feasibility analysis, environmental impact assessments and regulatory permits to proceed. Some regional mineral deposits and waste resources listed in this report are complex and relatively low grade, and conventional smelting and refining technologies (high-temperature processes) are most likely not feasible to convert these resources into high-value products required for the clean energy technologies. To address significant environmental impact concerns associated with mining, collection and processing of these materials, new processing technology approaches with reduced water and energy consumption and minimal environmental footprints are needed to support production of value-added products. Emerging hydrometallurgical processing technologies offer promising opportunities. This report provides a summary of the following: 1. Minnesota’s mineral and waste resources that have the highest potential for hydrometallurgical processing. 2. Challenges anticipated by stakeholders during the commercial development of mineral and waste resources using hydrometallurgical technologies. 3. Emerging hydrometallurgical innovations that may resolve various challenges identified by means of the stakeholder engagement survey. 4. Research priorities that support development of emerging hydrometallurgical technologies for Minnesota’s mineral and waste resources. 5. Bench-scale and semi-pilot laboratory tools that will allow NRRI to initiate research for advancing technological readiness level of emerging hydrometallurgical technologies. 1. Minnesota Resources Amenable to Hydrometallurgical Processing Minnesota possesses a variety of mineral and waste resources that could be efficiently and safely extracted and processed using hydrometallurgical technologies. These include: ● Copper-nickel-platinum group element (Cu-Ni-PGE) resources of northeastern Minnesota’s ~1.1- billion-year-old Duluth Complex, ● Nickel-copper-platinum group element (Ni-Cu-PGE) resources in satellite Mid-Continent Rift- related intrusive rocks such as those in the Tamarack Intrusive Complex, ● The ~1.1-billion-year-old titanium-iron vanadium deposits in oxide ultramafic intrusions (OUIs) along the western margin of Minnesota’s Duluth Complex, ● Copper-zinc deposits and gold-silver deposits associated with Minnesota’s ~2.7-billion-year-old greenstone belts, ● Iron-manganese (Fe-Mn) deposits in the Cuyuna District of east-central Minnesota, ● Aggregate and byproduct resources that occur across the state and which may contain recoverable quantities of critical metals, ● Incinerator ash from Minnesota’s coal-burning power plants and waste-to-energy facilities which can contain a variety of critical metals, and ● Electronic waste (e.g., e-waste or waste electrical and electronic equipment), which can contain a variety of critical metals. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 54 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance 2. Challenges and Opportunities Anticipated During Resource Development The study summarizes the challenges and constraints anticipated by various stakeholders during the commercial development of these resources as gathered through a VOC survey and ethnographic study. ● Domestic supply of critical metals: The United States is increasingly reliant on foreign imports for its domestic consumption of critical metals (Department of Interior, 2018). Advanced hydrometallurgical technologies are necessary to determine the feasibility of extracting critical minerals from domestic mine tailings, in-ground critical mineral resources, and recycled materials such as e-waste. ● Diversification of minerals economy: Fluctuating demand and price for iron and steel products causes frequent shutdowns to Minnesota iron ore mines, resulting in job losses and more frequent negotiation of taconite royalties with the State. Advanced hydrometallurgical processing facilities are necessary to support a diversified minerals economy and lessen the negative impact of downturns in the iron and steel industry. ● Impact of water quality: Predicting and managing water quality degradation from mining to minimize risks to human and environmental health is a key challenge facing the minerals industry. Advanced waste characterization tools may enhance the knowledge on potential environmental impacts of some of the less explored mineral and waste resources. ● Mercury impairment: Bioaccumulation of mercury in aquatic organisms is a concern to tribal authorities, as many tribes rely on fish for subsistence and cultural practices. Tribal authorities are concerned that existing impairments will make the cumulative effects of mercury from new or expanded mine discharges greater. Technologies that help to meet the Fond du Lac Band’s human health chronic mercury standard of 0.77 ng/L will assist the future industries to maintain social license to operate. ● Absence of local research laboratories: Current and prospective private and public mineral rights-holders and academic researchers rely on international laboratories to support their geometallurgical, advanced processing, and environmental testing and research programs, resulting in lengthy delays to complete the environmental impact assessments and process development programs. ● Reliance on foreign smelters for processing: Rising transportation, toll smelting, and refining costs negatively impact economic viability of local companies that may rely on international smelters for further processing of mineral concentrates. Research to evaluate the feasibility of producing value-added products regionally may help create domestic supply chain for critical metals, high value return to the state, and increase in jobs. ● Technology constraints: To meet stringent quality standards, conventional metallurgical smelters and refineries demand a high-quality concentrate with low impurity levels. However, historical studies have demonstrated technical difficulties to produce smelter grade concentrates from Minnesota’s ore copper, nickel, PGE, ilmenite, and manganese resources. For instance, the challenge with regional Cu-Ni-PGM concentrates has been to separate the Cu and the Ni into concentrates that have acceptable payabilities with acceptable recoveries. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 55 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance 3. Emerging Opportunities This research describes emerging areas that might benefit from application of hydrometallurgical technologies including: 1) Battery metal extraction from in-situ mineral and waste resources, 2) Critical metal extraction from waste tailings, low-grade ores, and urban wastes, 3) Mercury and heavy metal capture from metallurgical waste streams, and 4) Production of secondary products used in CO2 storage via carbon mineralization. 4. Key Research Priorities To support the development and commercialization of emerging technologies listed above, the following research and development priorities have been identified via the VOC survey: ● Define viable hydrometallurgical technologies to produce high-value materials from Minnesota’s mineral and waste resources; ● Explore the potential applications for hydrometallurgical techniques to understand the environmental impact of waste rocks and tailings via accelerated aging; and ● Understand the potential applications of hydrometallurgical techniques to create secondary products that could potentially allow CO2 sequestration. ● Explore hydrometallurgical technologies to reduce mercury concentration from potential process waste to below 0.77 ng/L (the Fond du Lac Band standard). Conceptual Design of a Hydrometallurgical Research Facility This research has identified capital required to support a laboratory and semi-pilot facility focused on developing emerging hydrometallurgical techniques for Minnesota’s mineral and waste resources. The key components supporting this research include: • Research tools required to support proof of concept studies, product development, flowsheet development, process optimization, and equipment scale-up strategies; • Research tools that allow bench-scale metal extraction studies from a wide variety of resources including but not limited to minerals, waste tailings, metallurgical waste, metallurgical residues, urban waste, incinerator ash, electronic waste, etc.; • Research equipment to characterize solid mine waste and liquid effluent from hydrometallurgical processes; • Simulation and modeling tools that estimates emissions, water, material, and energy requirements for emerging hydrometallurgical processes; • Skillsets and technical competencies that are required to conduct and manage hydrometallurgical research programs; and • Funding opportunities, research collaborators, and potential private and public partnerships to support the research program at NRRI. • The capital estimates for bench-top and semi-pilot laboratory prototypes range from $600,000 to $1.2 million. 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NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 57 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Glencore Technology, 2020. Albion Process™ – 2020 Compendium of Technical Papers, s.l.: s.n. Government of British Columbia, 2014. Mount Polley Mine Tailing Dam Breach. [Online] Habashi, F., 1993. A Textbook of Hydrometallurgy. Saint Foy(Quebec): Mettalurgie Extractive Quebec, Enr.. Habashi, F., 1996. The Sulfur Problem in the Metallurgical Industry. s.l., The Minerals, Metals, and Materials Society, pp. 825-841. Izatt, R., Izatt, S., Bruening, R. & Izatta, N., 2014. Challenges to achievement of metal sustainability in our high-tech society. Chemistry Society Review, pp. 2451-2475. 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Nano One Launches Groundbreaking M2CAM Technology to Reduce Cost, Waste and Carbon Footprint in Lithium-ion Battery Supply Chain. [Online] NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 58 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Nano One Materials Corp, 2021c. Groundbreaking M2CAM Technology to Reduce Cost, Waste and Carbon Footprint in Lithium-ion Battery Supply Chain. [Online] [Accessed 09 May 2022] National Academy of Engineering, 1998. Memorial Tribute. [Online] [Accessed August 2020] Nth Cycle, 2021. Clean, electro-extraction technology. [Online] Our Next Energy, 2021. Our Next Energy (ONE) Closes Series A Led by Breakthrough Energy Ventures. [Online] Parameswaran, K., Wilhelm, J. & Camorlinga, R., 2018. Sustainable Development Considerations in Primary Copper Smelting. In: Extraction 2018. s.l.:Springer, Cham, pp. 241-252. 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Teck, 2019, Satellite Assets - Mineral Reserves and Mineral Resource Disclosure: https://https://www.teck.com/media/Project%20-Satellite-Summary.pdf. Temple, J., 2021. A startup using minerals to draw down CO2 has scored funding—and its first buyer. [Online] NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 59 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Tusaar Corp, 2022. Tusaar Corp. [Online] U.S. Congress, Office of Technology Assessment, 1990. Nonferrous Metals: Industry Structure, Washington: U.S. Government Printing Office. U.S. Department of Energy - Office of History and Heritage Resources, 2005. The Manhattan Project: An Interactive History. [Online] [Accessed August 2020] U.S. Department of State, 2021. The Long-Term Strategy of the United States: Pathways to Net-Zero Greenhouse Gas Emissions by 2050., Washington DC: United States Department of State and the United States Executive Office of the President. U.S. Environmental Protection Agency, 2021. Overview of CWA Section 401 Certification. [Online] [Accessed 06 January 2022] U.S. Environmental Protection Agency (EPA), 1994. Acid Mine Drainage Prediction, Washington: s.n. U.S. Geological Survey, 2021. Earth Mapping Resources Initiative (Earth MRI). [Online] U.S. Geological Survey (USGS), 2017. 2017 Minerals Yearbook: Copper, s.l.: s.n. United Nations, 2022. 17 Sustainable Development Goals (SDGs). [Online] [Accessed 13 May 2022] VoltStorage GmbH, 2021. Iron-Salt Technology: World's Most Cost Efficient Battery Technology. [Online] Wicks, D., 2022. Avenues to Realize Carbon Negative Mineral Extraction. Minneapolis, Minnesota Minerals & the Green Economy Forum. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 60 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance APPENDICES NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 61 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendices Table of Contents List of Figures .............................................................................................................................................. 64 List of Tables ............................................................................................................................................... 65 Appendix A: Hydrometallurgical Research Equipment ............................................................................... 66 A.1. Hydrometallurgy Laboratory Equipment ......................................................................................... 67 A.1.1. Atmospheric Leaching, Precipitation, and Crystallization Reactors ......................................... 67 A.1.2. High-Pressure Leaching and Mineral Carbonization Reactors ................................................. 68 A.1.3. Mine Rock Characterization via Accelerated Aging .................................................................. 68 A.1.4. Advanced Solution Purification Equipment .............................................................................. 68 A.1.5. Bench Scale Electrowinning Pilot Plant .................................................................................... 69 A.1.6. Solid-Liquid Separation Equipment .......................................................................................... 69 A.1.7. Column chromatography .......................................................................................................... 69 A.1.8. Analytical Tools ......................................................................................................................... 69 A.1.9. Process Modeling, Simulation and Statistical Analysis Tool ..................................................... 70 A.2. Advanced Mineral Processing .......................................................................................................... 71 A.2.1. Sample Preparation Equipment ............................................................................................... 71 A.2.2. Advanced Laboratory Grinding Equipment .............................................................................. 71 A.2.3. Advanced Beneficiation Equipment ......................................................................................... 72 Appendix B: Emerging Hydrometallurgical Technologies ........................................................................... 73 B.1. Battery Metal Extraction Processes ................................................................................................. 74 B.1.1. One-Pot Process ........................................................................................................................ 74 Potential Applications to Minnesota Resources ..................................................................................... 74 B.1.2. Battery Grade Nickel Sulfate Production .................................................................................. 77 Potential Applications to Minnesota Resources ..................................................................................... 81 B.1.3. Battery Grade Manganese Sulfate Production ......................................................................... 81 Potential Applications to Minnesota Resources ..................................................................................... 82 B.1.4. Direct Nickel Process (DNi-Process) .......................................................................................... 83 Potential Applications to Minnesota Resources ..................................................................................... 84 B.1.5. Hydro-to-Cathode Technology ................................................................................................. 84 Potential Applications to Minnesota Resources ..................................................................................... 84 B.1.6. Li-Cycle ...................................................................................................................................... 86 Potential Applications to Minnesota Resources ..................................................................................... 86 B.1.7. Iron Salt Technology and Vanadium Redox Flow Technology .................................................. 86 B.1.8. Mitra Chem Technologies -Lithium Iron Phosphate Batteries ................................................. 86 Potential Applications to Minnesota Resources ..................................................................................... 86 B.2. Critical Metal Extraction from Low-Grade Ores and Waste Tailings ............................................... 88 B.2.1. Lilac Solutions ........................................................................................................................... 88 Potential Applications to Minnesota Resources ..................................................................................... 88 B.2.2. Jetti Resources .......................................................................................................................... 88 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 62 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Potential Applications to Minnesota Resources ..................................................................................... 89 B.2.3 Phoenix Tailings ......................................................................................................................... 89 Potential Applications to Minnesota Resources ..................................................................................... 89 B.2.4. Nth Cycle ................................................................................................................................... 89 Potential Applications to Minnesota Resources ..................................................................................... 89 B.3. Carbon Mineralization Technologies ............................................................................................... 89 B.3.1. Carbfix ....................................................................................................................................... 89 Potential Applications to Minnesota Resources ..................................................................................... 90 B.4. Mercury and Selenium Removal Technologies ................................................................................ 90 B.4.1. Sulfur based sorbents ............................................................................................................... 90 B.4.2. Tusaar Corp ............................................................................................................................... 90 B.4.3 Zero Valent Iron (ZVI) technology .............................................................................................. 90 B.4.4. Advanced Biological Metals (ABMet) technology .................................................................... 90 B.4.5. Saturated Rock Fill (SRF) Technology ........................................................................................ 90 B.4.6. Membrion Technologies ........................................................................................................... 90 Potential Applications to Minnesota Resources ..................................................................................... 91 B.5. Demonstrated Hydrometallurgical Technologies for Regional Mineral Resources ......................... 91 B.5.1. Cominco Engineering Services Limited (CESL) .......................................................................... 91 B.5.2. PLATSOL™ ................................................................................................................................. 94 B.5.3. Albion Process™ ........................................................................................................................ 96 Appendix C: Existing Hydrometallurgical Technologies .............................................................................. 98 C.1. Commercial Plant Operations in North America ............................................................................. 99 Appendix D: Mineral Resources of Minnesota ......................................................................................... 116 D.1. Mineral Resources of Minnesota ................................................................................................... 117 D.1.1. Non-ferrous Resources ........................................................................................................... 117 D.1.2. Ti-V Resources of the Duluth Complex ................................................................................... 123 D.1.3. Ferrous Resources .................................................................................................................. 124 D.2. Aggregate and Byproduct Resources............................................................................................. 131 D.2.1.Byproducts............................................................................................................................... 131 Appendix E: Waste Resources of Minnesota ............................................................................................ 135 E.1. Waste Resources in Minnesota ...................................................................................................... 136 E.1.1. Waste-to-Energy Facilities in Minnesota ................................................................................ 136 E.1.2. Coal Combustion Residuals ..................................................................................................... 136 E.1.3. Waste Electrical and Electronic Equipment (WEEE) ................................................................... 137 Appendix F: Short Case Study on Vale’s Long Harbour Hydrometallurgical Processing Plant ................. 139 F.1. Introduction.................................................................................................................................... 140 F.2. Nickel Sulfide Ores ......................................................................................................................... 140 F.2.1. Typical Processing of a Nickel Sulfide Ore............................................................................... 140 F.2.2. Smelting vs. Hydrometallurgical Processing of Nickel Concentrate ....................................... 141 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 63 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance F.3. Voisey’s Bay Mill ............................................................................................................................. 142 F.3.1. Deposit .................................................................................................................................... 142 F.3.2. Process .................................................................................................................................... 142 F.3.3. Decision for Hydrometallurgical Processing ........................................................................... 143 F.4. Long Harbour Processing Plant ...................................................................................................... 143 F.4.1. Process .................................................................................................................................... 143 F.4.2. Plant Construction and Commissioning .................................................................................. 144 Appendix G: Biohydrometallurgical Technologies .................................................................................... 145 G.1. Review of Biohydrometallurgy ...................................................................................................... 146 G.2. Commercial Applications of Biohydrometallurgy in Mining Sulfidic Ores .................................... 146 G.2.1. Bioleaching-Heap Reactors .................................................................................................... 146 G.2.2. Bioleaching-Stirred Tank Reactors ......................................................................................... 147 G.3. Application of Bioleaching to Non-sulfide Ores (Manganese ores) .............................................. 148 G.4. Applications in Bioremediation in the Minerals Industry .............................................................. 148 G.4.1. Sulfate Removal ...................................................................................................................... 148 G.4.2. Biosorption of Metals from Wastewater ............................................................................... 148 G.5. Application of Biohydrometallurgy to Minnesota’s Mineral Resources ....................................... 149 G.5.1 Development of Engineered Biosorbent from Minnesota Biomass ....................................... 149 Appendix H: Application of Hydrometallurgy to Mine Wastewater Treatment ....................................... 151 Application of Hydrometallurgy to Mine Wastewater Treatment ....................................................... 152 H.1. Importance .................................................................................................................................... 152 H.2. Existing Mine Wastewater Treatment Technologies ..................................................................... 152 H.3. Case Study 1: Water Treatment Plant at Eagle Mine LLC, Michigan ............................................. 154 H.4. Case Study 2: Proposed Wastewater Treatment Plant at the NorthMet Project ......................... 154 Appendix I: List of High Value Products .................................................................................................... 158 Appendix J: List of Historical Hydrometallurgical Studies at NRRI ............................................................ 161 References ................................................................................................................................................ 163 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 64 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance List of Figures Figure 7. Comparison of traditional cathode process vs. Nano One® One-Pot Process for cathode manufacturing ................................................................................................................................ 75 Figure 8. Hydrometallurgical flowsheet for the production of battery grade nickel products .................. 78 Figure 9. Hydrometallurgical flowsheet proposed for Tamarack deposit .................................................. 79 Figure 10. Traditional hybrid pyrometallurgical and hydrometallurgical flowsheet used in production of nickel sulfate ........................................................................................................... 80 Figure 11. Hydrometallurgical flowsheet used in the production of high-purity electrolytic manganese metal ........................................................................................................................... 82 Figure 12. Process flowsheet for Direct Nickel Process .............................................................................. 83 Figure 13. Flowsheets comparing Hydro-to-Cathode™ with traditional hydrometallurgical and pyrometallurgical treatment of end-of-life batteries .................................................................... 85 Figure 14. Hydrometallurgical process used by Li-Cycle for the treatment of end-of-life batteries .......... 87 Figure 15. Process flowsheet for Jetti Process ............................................................................................ 88 Figure 16. CESL hydrometallurgical flowsheet developed for the Mesaba deposit ................................... 93 Figure 17. PLATSOL™ hydrometallurgical flowsheet developed for the NorthMet Project ....................... 95 Figure 18. General schematic for the Albion Process™ .............................................................................. 96 Figure 19. A map of commercial non-ferrous metallurgical operations in North America ...................... 100 Figure 20. Medium-temperature pressure oxidation process practiced at Freeport McMoran's Morenci facility, AZ, USA .............................................................................................................. 108 Figure 21. Pressure oxidation leaching process practiced at Voisey's Bay Long Harbor facility .............. 109 Figure 22. Biological leaching process practices at Terrafame in Sotkamo, Finland ................................ 110 Figure 23. Chloride-based autoclave pressure leaching practiced at Glencore’s Nikkelverk, Kristiansand in Norway ................................................................................................................ 111 Figure 24. Hydrometallurgical flowsheet used in the extraction of platinum group elements at Rustenburg, South Africa ............................................................................................................. 112 Figure 25. Hydrometallurgical process used in the production of high-purity titanium dioxide slag in Quebec, Canada ....................................................................................................................... 113 Figure 26. Hydrometallurgical process flowsheet used in the production of electrolytic manganese metal in China ........................................................................................................... 114 Figure 27. Hydrometallurgical flowsheet practiced at Sibanye Stillwater Complex in Montana, USA ............................................................................................................................................... 115 Figure 28. Location map of identified non-ferrous mineral resources in Minnesota ............................... 118 Figure 29. Bedrock geology and mineral resource location map of the contact-type deposits of the Duluth Complex and adjacent areas ...................................................................................... 119 Figure 30. Bedrock geologic map of the Tamarack Ni-Cu-Co-PGE conduit-type sulfide deposit ............. 122 Figure 31. Bedrock geologic and location map of Ti-Fe-V resources associated with cross-cutting oxide-ultramafic intrusions of the western Duluth Complex ...................................................... 123 Figure 32. Location map of identified ferrous mineral resources in Minnesota ...................................... 124 Figure 33. Bedrock geology and iron mining features of the Mesabi Iron Range .................................... 126 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 65 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 34. Bedrock geology and open pit Fe-Mn mine map of the North Range of the Cuyuna Iron Range .................................................................................................................................... 127 Figure 35. Bedrock geology and location map of properties outlined in reports by Strong (1959) and Beltrame, et al. (1981) that includes manganese grade-tonnage estimates ....................... 130 Figure 36. Distribution of aggregate and byproduct resources within Minnesota .................................. 132 Figure 37. Comparison of tailings compositions (Zanko, et al., 2003) relative to a bulk earth composition (Hickey, et al., 1986) ............................................................................................... 133 Figure 38. Comparison of tailings compositions (Zanko, et al., 2003) relative to the North American Shale Standard (Gromet, et al., 1984) ......................................................................... 133 Figure 39. Map of waste-to-energy, e-waste recycling, and coal-fired power plants in Minnesota. ....... 138 Figure 40. Main process steps for extracting nickel and cobalt from sulfide ores ................................... 141 Figure 41. Voisey's Bay mill flow sheet design circa 2005 ........................................................................ 142 List of Tables Table 9. Product specification for battery grade nickel sulfate .................................................................. 77 Table 10. Product specification for battery grade manganese sulfate (adapted from Future Battery Industries Cooperative Research Centre, 2020). .............................................................. 81 Table 11. Mixed hydroxide precipitate generated from the Mesaba pilot campaign ................................ 92 Table 12. Comparison of CESL, PLATSOL™, and Albion Process™ .............................................................. 97 Table 13. A list of non-ferrous metallurgical extraction facilities in North America ................................ 101 Table 14. Ni 43-101 compliant grade-tonnage estimates of mafic magmatic sulfide deposits associated with the Mid-Continent Rift ....................................................................................... 120 Table 15. Reported grade/tonnage of active taconite operations ........................................................... 125 Table 16. Manganese grade and tonnage estimates from reports by Strong (1959) and Beltrame, et al. (1981) .................................................................................................................................. 129 Table 17. Summary of aggregate and byproduct resources in Minnesota ............................................... 131 Table 18. Summary of coal combustion residual generating facilities in Minnesota. .............................. 136 Table 19. List of bio-heap leaching plants ................................................................................................. 147 Table 20. Biosorption capabilities of killed biomass ................................................................................. 149 Table 21. List of commercially practiced wastewater treatment technologies at mine sites. ................. 153 Table 22. Wastewater treatment facility preliminary water quality targets ............................................ 155 Table 23. Surface water quality evaluation criteria applicable to different classes of surface water ............................................................................................................................................ 157 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 66 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix A: Hydrometallurgical Research Equipment Appendix A presents a descriptive list of research equipment that is necessary or useful in developing processes and is arranged by different hydromet process subcategories. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 67 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance A.1. Hydrometallurgy Laboratory Equipment The hydrometallurgy laboratory will house metal extraction, mine wastewater treatment, waste characterization, and carbon mineralization equipment. The following equipment list is not exhaustive, but it highlights strategically important tools that are necessary to meet the research needs of stakeholders. A.1.1. Atmospheric Leaching, Precipitation, and Crystallization Reactors Bottle roller: Bottle roll tests are the industry standard for assessing the metal recovery possible by atmospheric leaching and provide information on expected recovery rates, reagent costs, and required addition rates. They also provide an indication of the results from the pilot plant and commercial scale leach circuit. These tests can deliver the following data: recovery of metals, leach kinetic data, and plots for all metals tracked and acid consumption with leach time data and curves. Armfield reactors: This benchtop unit can simulate five different reactor types: continuous stirred reactor, tubular reactor, batch reactor, laminar flow reactor, and plug flow reactor. This unit is a fully computer controlled unit supplied with a hot water re-circulator used to control the temperature of the reactions, glass feed vessels for the reactants, two peristaltic pumps to pump the reagents to the reactors, computer software for data logging, sensors, and instrumentation. Applikon Dependable Instruments benchtop reactor: This jacketed reactor system is used in academic, government, and industrial laboratories for process development in laboratory scale. The system is equipped with a glass reactor, gas flow controllers and rotameters, spargers, condensers, sensors, controllers, valves, and tubing. The reactors are available in 2, 3, 5, 7, 15, and 20L (0.5gal to 5gal) total volume. The system is equipped with a controller that provides programmable control and optimization of system parameters such as dissolved oxygen concentration, pH level, RedOx potential, temperature, turbidity, and stirring speed. The software that accompanies the system enables process data acquisition and storage. Büchi AG miniPilot reactor: The Büchi miniPilot reactor is an ideal tool for hydrometallurgical process development, process simulation and kilo-scale production. The system is supplied with interchangeable reactors of 5, 10, and 15 liters including interchangeable stirrers, sampling devices, pH probes, process monitoring, and control. The explosion-proof design and inert materials allow safe processing of solvents and acids in a completely sealed reaction vessel. With permissible operating range for pressure between -1.0 (full vacuum) to +1.0 bar and temperature between -60 °C to +200 °C, the system is suitable for simulation of atmospheric leaching at low, medium, and high-temperatures. Column leach reactor: A column reactor is chiefly used to 1) simulate biological heap leaching of metallic ore samples, 2) determine the oxidation rate, sulfate production, and metal release from waste rocks or tailings, and 3) study filtration or adsorption behavior of various sorbents or filter media. The leaching column is made of PVC and stainless steel. It has a stainless steel solution tank with a sampling point, valves, and a variable speed pump to control the flow rate of reagents through the column. A 10-mesh stainless steel screen covers the drain plate at the bottom of the column to prevent fine-grained material from plugging the recirculation pump. A peristaltic pump is used to re-circulate the leach solution. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 68 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Bench scale leach pilot plant: This setup is ideal to simulate an atmospheric leaching process for the continuous production of leach solution to support downstream metal recovery processes. The setup includes 1) feed preparation tank with tank cover, baffles, and overhead agitator, 2) variable speed slurry feed pump, 3) four cascading leach vessels with covers, baffles, and overhead agitators, 4) immersion heaters with temperature controllers, 5) reagent delivery burettes, Teflon stopcocks incorporating needle metering valves, 6) reagent feed tank with metering pump, and 7) discharge tanks with tank covers. A.1.2. High-Pressure Leaching and Mineral Carbonization Reactors Parr bench-top autoclave reactors: These bench-top autoclaves are ideal tools to conduct oxidative leaching and mineral carbonization studies of mineral ore samples. Parr offers a number of different reactors in a variety of sizes and with different mountings for operating pressures to 5000 psi (345 bar) and temperatures to 500 °C. The system is also supplied with a wide range of accessories for feeding of liquids or solids or gas into the reactor. Parr controllers offer PID control with auto tune, ramp and soak programming, separate heating and cooling control loops, stirrer motor speed control, full or half power heater option, lockout relay and reset for over temperature protection, expansion modules for tachometer, pressure, and high temperature alarm. A.1.3. Mine Rock Characterization via Accelerated Aging Parr multiple reactor system: Historically, humidity cell tests are used to: 1) simulate the geochemical weathering (natural oxidation) processes, usually at an accelerated rate, 2) determine the rate of acid generation and variation over time in leachate water quality, and 3) provide a preliminary assessment of acid rock drainage (ARD) control options. However, a humidity cell test is typically run for ten weeks and follows a seven-day cycle. As a result, tests might require a long time for completion with correspondingly high costs. Moreover, confirmation of acid rock drainage potential from the humidity cell is often inconclusive due to the time required to deplete neutralization potential to levels at which acid generation becomes measurable. To accelerate the aging by several orders of magnitude, a multiple pressure reactor system is proposed by NRRI. The pressure reactor system uses a combination of pressure, temperature, and oxidizing gasses to accelerate the acid generation and sulfate oxidation. This accelerated approach may provide an assessment of leachate quality and dissolved metal flux that could be expected from waste rocks or mine tailings. The proposed multiple pressure reactor system uses a combination of sixteen standard autoclaves with heaters, valves, pressure gages and rupture disc assemblies and two 4871 Process Controllers with sixteen 4875 Power Controllers. It allows the user to run multiple reactions simultaneously, applying the principles of high-throughput experimentation. Individual variables that can be controlled are gas mixtures, liquids, catalysts or other solids, stirring speed, temperature, pressure, and time. A.1.4. Advanced Solution Purification Equipment Liquid-liquid separation consists of transferring metal ions contained in feed solution into an immiscible solvent. The solvent that is enriched in metal ions is called extract, while solution deprived of metal ions is referred to as raffinate. The following section describes tools used in developing solvent extraction processes in lab and bench-scale. Laboratory Solvent Extraction Equipment Orbital shakers, centrifuge mixers, variable wrist action shakers, incubator shakers, etc., support lab-scale investigations focusing on selectively separating targeted metal ions from leach solutions via solvent extraction processes. These tools are used in screening organic extractants NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 69 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance to selectively extract a targeted metal ion from solution. Additionally, they help in determining reaction time, temperature, extractant concentration, pH, number of stages, and optimal aqueous-to-organic phase ratio of extraction, scrubbing, and stripping based on McCabe-Thiele diagrams. Rousselet Robatel mixer settler: While lab-scale mixers allow flow sheet design to determine the number of stages and optimal aqueous-to-organic phase ratio of extraction, scrubbing, and stripping steps, Rousselet Robatel mixer-settlers help to evaluate the possibility of scaling up the process and/or producing larger volumes of purified metal solution in a continuous counter current mode. A lab-scale mixer-settler consists of a mixing chamber where an agitator brings the feed solution in intimate contact with organic solvent. A subsequent settling chamber allows static decantation of the two phases, whereas the coalescence plates facilitate the separation of emulsions into light and heavy fractions. The two fractions then pass to subsequent purification stages by overflowing through the light phase and heavy phase weirs. Bench Scale Solvent Extraction Pilot Plant: The MAEB bench-scale mini-pilot unit is suitable for flowsheet evaluation, pilot plant operation, and small-scale production. Mixer-settlers can be arranged into multiple stages to simulate extraction, scrubbing, and stripping stages. Each active mixer volume is 0.12 liter, and the settler volume is 0.48 liter with a loading surface area of 0,006 m2. Recommended maximum total flow (organic + aqueous + recycle) is 10 l/h at normal settling velocity. The mixer-settler units are available in polymethyl methacrylate (PMMA) or polyvinylidene fluoride (PVDF) plastics, with the former allowing visual inspection of operation while the latter resists corrosive attacks and is suited for work in the temperature range up to 80° C. A.1.5. Bench Scale Electrowinning Pilot Plant This bench-scale electrowinning unit is suitable for pilot plant operation and small-scale production. The process is suitable to recover copper, nickel, gold, cobalt, and other metals from purified solutions obtained from the solvent extraction process. The cathodes used in the cells can be manufactured from various metals including 316L stainless steel and titanium, whereas anodes can be made from lead-calcium-tin (Pb-Ca-Sn) and Lead-silver (Pb-Ag) alloys. A.1.6. Solid-Liquid Separation Equipment 1. Benchtop filter press: A plate filter press allows separation of solids from liquids. By allowing separation of leach liquor from undissolved solids, the filter press allows the generation of leach solutions for downstream metal recovery processes like precipitation, solvent extraction, ion exchange, and adsorption. Additional applications include cake recovery, low solids recovery from precipitation, or clarification processes. 2. Laboratory candle filter: The candle filter allows lab-scale solid liquid separation of products from bench-scale leaching, precipitation, and crystallization processes. A.1.7. Column chromatography 3. Lab-scale chromatography helps to screen ion-exchange resins and adsorbents for selective separation of metals from various diluted streams. A.1.8. Analytical Tools 4. ICP-MS: Inductively coupled plasma mass spectrometry (ICP-MS) is an elemental analysis technology capable of detecting most of the periodic table of elements at milligram to NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 70 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance nanogram levels per liter – making ICP MS a preferred choice over ICP OES and AAS for performing trace element analysis. 5. QEMSCAN: QEMSCAN is an acronym for Quantitative Evaluation of Materials by Scanning Electron Microscopy. It utilizes Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS) to create an image of a sample based on chemical composition. These images can be processed to provide information about the chemical and mineral composition of the sample, as well as the textures, mineral abundances, mineral associations, grain sizes, liberation characteristics, surface exposures, etc. A.1.9. Process Modeling, Simulation and Statistical Analysis Tool HSC Chemistry 10: This software toolkit allows thermochemical and mineral processing calculations that are useful during process research and development as well as for estimating process efficiencies, yields, and environmental footprints. The salient features of this tool include: ● HSC provides the heat of the reactions, the equilibrium constant at any temperature and number of species. The calculated heat of reaction is the amount of heat that will be absorbed or released in the reaction and the equilibrium constant predicts the direction of the reaction. ● HSC helps to carry out heat balance calculations, thus allowing estimating the energy requirements and the cost of the process, as well as the operation preconditions. ● HSC is capable of calculating the environmental impact of a reactor, section, or total plant developed in the HSC Sim module. ● HSC helps to draw phase stability diagrams, which show the stability (predominance) areas of condensed phases in a ternary system as a function of temperature or in isothermal conditions with the remaining constraints on the other axis. These diagrams are very useful when a fast estimation of the prevailing phases is needed. ● HSC helps to generate Eh-pH diagrams that illustrate the stabilities of ionic and non- ionic species in water solutions. This knowledge is critical to understanding problems of corrosion, dissolution, leaching and selective precipitation. • HSC’s mass balance module helps to estimate the performance of a process, detect bottlenecks in the circuit, and to create models of the processing stages. METSIM®: This software is a general-purpose process simulation system designed to assist the engineer in performing mass and energy balances of complex processes. Stat-Ease Design-Expert Software: This software provides tools to design an ideal experiment on a process, screen for vital factors and components, characterize interactions, and help visualize the response surface from all angles with rotatable 3D plots. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 71 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance A.2. Advanced Mineral Processing A.2.1. Sample Preparation Equipment The following section lists sample preparation and comminution equipment necessary to compliment the hydrometallurgical testing. Laboratory oven: a forced-air convection oven provides controlled heat to dry drill core samples, run of mine ores, bulk ore samples, comminution, and beneficiation test samples. Splitters: Sample splitters and reducers ensure the test sample has materials with particle sizes in representative portions to original or bulk material. Sieves and sieve shaker: ISO 565, 3310-1 allows determination of particle size distribution of test samples. Screen trays and screen shakers: The screen trays have areas much larger than round test sieves and allow particle size determinations on large samples of ores and coarse materials from 4” (101 mm) to 14 mesh (1.4 mm) sizes. Laboratory crushing: Laboratory jaw crusher, cone crusher, and rolls crusher enable particle size reduction of test samples from 4” to 14 mesh (1.4 mm). Traditional laboratory grinding equipment: Batch-type laboratory ball mill and rod mill helps in preparation of test samples for laboratory beneficiation tests. Typical functions include grinding the ore samples to achieve mineral liberation. A.2.2. Advanced Laboratory Grinding Equipment Magotteaux mill: This laboratory mill is designed to simulate the physical (particle size distribution) and chemical conditions (Eh, pH, temperature, dissolved oxygen, etc.) of the plant grinding mill. The mill runs at variable speed with temperature control and continuous chemistry monitoring, thus allowing the study of the impact of grinding media and the resulting grinding chemistry on downstream beneficiation processes, including froth flotation and leaching. M4 IsaMill: This fine grinding mill produces steep particle size distribution without needing internal screens or closed circuit hydrocyclones, which are favorable in flotation and leaching processes. The pilot scale unit determines power requirements while investigating media consumption and downstream processing performance on real plant streams. Attritor mill: In this laboratory stirred ball mill, the material to be ground is placed in a stationary tank with the grinding media, which are agitated by a shaft with arms rotating at high speed. Working at 10 times faster than conventional laboratory ball mills, the Attritor mill allows wet or dry grinding, introduction of inert atmospheres, operation at controlled temperatures, varying grinding speed, product contamination, changing media size and type, while obtaining precise energy consumption information. 6. Classification Laboratory hydrocyclone rig: This rig enables closed circuit grinding, finer particle separation and enrichment, desliming, and thickening of mineral samples. These rigs are ideal to obtain cut sizes from 1000 µm down to 3-4 µm. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 72 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance A.2.3. Advanced Beneficiation Equipment Mozley superpanner: This laboratory unit is suitable to evaluate the amenability of ore samples to gravity separation. The sample requirements are small (few 100g), making it possible to use this technique when insufficient material is available for larger scale tests such as spiral testing. Reflux classifier: This technology is emerging as the industry standard for fine gravity separation. It consists of a lower fluidized bed section and an upper section of parallel inclined channels. This combination provides both a gravity separation and deslime of the feed. Magotteaux float cell: This laboratory flotation machine comes with a bottom-driven agitator that allows operators to uniformly remove froth from the entire surface of the cell, thus minimizing operator errors while maximizing test reproducibility. The equipment also allows continuous monitoring of pulp chemistry throughout the test as the probes remain in the pulp. LAARMANN computerized laboratory flotation cell: This laboratory flotation machine allows digital control of cell level, agitator speed, airflow rate, and automatic froth remover. The technology uses stainless steel, acrylic, polyurethane, and PTFE coating as materials of construction, thus making it suitable for hot slurry and corrosive applications. Ore sorting: By continuously measuring color, atomic density, or conductivity of test samples, sorters selectively separate the valuable mineral ores from waste rocks using a pulse of pressurized air directed with precision by an amplified mechanical, hydraulic, or pneumatic process. By eliminating waste rocks at the early stages of processing, sensors not only minimize the consumption of energy, water, and reagents, but also reduce the carbon footprint of the extraction process. L150 laboratory Jameson Cell: By utilizing fine bubbles and intense mixing between air and bubbles, Jameson cells maximize bubble particle attachment to maximize concentrate recovery while upgrading concentrate grade through its integrated wash water system. This allows the Jameson Cell to achieve flotation targets in a single stage that would normally require several stages with conventional cells, thus reducing the footprint of the installation. The laboratory cell is appropriate for testing on small batches of samples (between 20-40 kg) or for small-scale continuous operation (~390L/hour). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 73 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix B: Emerging Hydrometallurgical Technologies Appendix B lists emerging technologies and provides a section on relevance to Minnesota. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 74 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance B.1. Battery Metal Extraction Processes B.1.1. One-Pot Process Nickel sulfate is the preferred feedstock for conventional battery cathode manufacturing (Campagnol, et al., 2017) but this process presents several disadvantages (Tesla, 2020). Nickel ore is mined, crushed, concentrated, and upgraded to nickel matte using a pyrometallurgical smelting process. Subsequent hydrometallurgical processes consisting of leaching, solvent extraction, precipitation, and electrowinning techniques convert the nickel matte into nickel metal, which is crystallized to produce nickel sulfate (Talon Metals Corp, 2021). This process consumes large amounts of water and chemicals, while generating large amounts of wastewater and byproducts. To overcome these issues, Nano One Materials, a Vancouver based start-up has developed a “one-pot process” for the production of cathode materials directly from metal powders (Figure 7). The technology combines feedstock conversion, precursor formation, and lithiation and coating steps into one reaction. Benefits include: 1) by using metal powders instead of metal sulfate compounds, the process eliminates the generation of sulfur and wastewater streams; 2) because nickel metal powder weighs one-fifth the weight of nickel sulfate, the process eliminates the shipment of water and sulfur, thereby reducing the transportation costs; 3) the process also eliminates the need for costly and energy-intensive crystallization steps, which is traditionally used in conversion of metal powders to metal sulfates or hydroxides; and 4) by eliminating the generation of sulfate based byproducts and wastewaters, the process eliminates the environmental cost of handling waste stream of water and sulfate (Figure 7; Nano One Materials Corp., 2021). Tesla’s Battery Day presentation hints at using a similar process as one-pot process to manufacture cathodes for their electric vehicle battery pack (Tesla, 2020). Potential Applications to Minnesota Resources The possibility of using One-Pot process technology to produce cathode active materials using Minnesota’s nickel resources requires further technical evaluation. Prospective mining business models rely on international smelters to process their nickel sulfide concentrate, which could lead to loss of revenues to the State of Minnesota. However, stakeholders interested in adopting the “mine-to- cathode” approach could benefit by integrating “one-pot process” into their hydrometallurgical complex. The potential benefits of this approach include: ● Allows conversion of class 1 nickel products to cathode active materials ● Offers an alternative to pyrometallurgical processes (e.g., smelting and refining), which require large capital investments, making it difficult for new players to enter the market ● Supports the diversification of the product portfolio from State’s nickel resources ● Enhances the royalty value of minerals owned by the State NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 75 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 7. Comparison of traditional cathode process vs. Nano One® One-Pot Process for cathode manufacturing (adapted from Nano One Materials Corp, 2021). Traditional cathode manufacturing from metal sulfate NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 76 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 77 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance B.1.2. Battery Grade Nickel Sulfate Production Nickel sulfate is a primary raw material for the production of lithium nickel cobalt manganese (NCM) and lithium cobalt aluminum oxide (NCA) batteries (Future Battery Industries Cooperative Research Centre, 2020). Battery manufacturers desire tight control over the impurities present in the nickel sulfate, which is critical for maintaining chemical stability and performance of batteries. In addition, uniform and fine crystals with zero-level moisture content and dust contamination are required. Several compositions of nickel sulfate used in battery manufacturing are shown in Table 9. Table 9. Product specification for battery grade nickel sulfate Element Australia Europe China Ni (%) 22 22 22 Co (ppm) 40-120 2-10 10-30 Cu (ppm) 1-9 1-2 1-1 Al (ppm) 1 1 10 As (ppm) 1-2 1 2 Ca (ppm) 1-2 1 5-7 Cd (ppm) 1 1-2 1-10 Cr (ppm) 1 1 3 Fe (ppm) 1-6 1-2 2-10 K (ppm) 1 1 - Mg (ppm) 1-4 1 20 Mn (ppm) 1 1 - Na (ppm) 1-5 5 30 P (ppm) 1 2 - Pb (ppm) 1 1-2 5-10 Si (ppm) 1-2 5 10 Zn (ppm) 1-5 1-2 1-10 Nickel sulfate can be produced using a variety of intermediate nickel products like nickel matte, mixed sulfate precipitate (MSP) and mixed hydroxide precipitate (MHP) or via Class 1 nickel products such as high-purity nickel metal powders or briquettes (Future Battery Industries Cooperative Research Centre, 2020). An example of a hydrometallurgical process used in the production of battery-grade nickel sulfate directly from nickel sulfide concentrate is shown in Figure 8. The process consists of pressure oxidative leaching of nickel sulfide concentrate followed by a solvent extraction process to separate cobalt and copper ions from the pregnant leach solutions. These ions are further stripped from the organic phase and precipitated as mixed sulfide products. The raffinate from the cobalt and copper solvent extraction process passes through an additional solvent extraction stage to separate nickel ions. Subsequent stripping of the organic phase results in a nickel rich aqueous solution. Finally, a crystallization process is used to precipitate nickel sulfate powders from this aqueous phase. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 78 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance In Minnesota, Talon Metals has recently completed a flowsheet design (Figure 9) to produce nickel sulfates directly from the Tamarack nickel sulfide concentrates (Talon Metals Corp, 2021), which is similar to the one described above. Figure 10 shows the traditional hybrid pyrometallurgical and hydrometallurgical flowsheet that is used to produce nickel sulfate from nickel mineral concentrates. Figure 8. Hydrometallurgical flowsheet for the production of battery grade nickel products (adapted from Future Battery Industries Cooperative Research Centre, 2020). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 79 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 9. Hydrometallurgical flowsheet proposed for Tamarack deposit (adapted from Talon Metals Corp, 2021). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 80 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 10. Traditional hybrid pyrometallurgical and hydrometallurgical flowsheet used in production of nickel sulfate(adapted from Talon Metals Corp, 2021). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 81 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Potential Applications to Minnesota Resources Historical nickel recovery methods from Cu-Ni ± PGE mineralization in Minnesota have followed three different processing routes. These include: ● Conventional processing comprising a flotation concentrator that produced smelter grade nickel concentrates ● A hydrometallurgical process that included a pressure oxidation leaching (PLATSOL™ and CESL) to process nickel concentrates into upgraded nickel-cobalt hydroxide ● A hydrometallurgical process that included an atmospheric oxidative leaching (ALBION Process™ and Mixed-Chloride Technology) to solubilize nickel from nickel concentrates. Each of these routes is limited to producing intermediate nickel products like mixed hydroxide precipitate and are not optimized for producing battery-grade nickel products. As nickel sulfate is the preferred feedstock of battery manufacturers, further technical evaluation should focus on developing environmentally benign methods to produce nickel sulfate directly from local nickel concentrates. The potential benefits of this approach include: ● Offers an alternative to pyrometallurgical processes (e.g., smelting and refining), which require large capital investment, thus making it difficult for new players to enter the market, ● Supports the diversification of the product portfolio from State’s nickel resources, and ● Enhances the royalty value of minerals owned by the State. B.1.3. Battery Grade Manganese Sulfate Production High-purity manganese sulfate monohydrate (HPMSM) is used as a precursor material for lithium nickel cobalt manganese (NCM) and lithium manganese oxide (LMO) batteries. Battery-grade HPMSM must contain a minimum of 31.8% Mn by weight. Alkali and alkaline cations negatively affect high- temperature morphology and cycling performance of Li-ion batteries. An impurity of concern is the element selenium. Due to safety issues surrounding the toxicity of hydrogen-selenide, battery manufacturers limit the selenium concentration to 3 ppm (Future Battery Industries Cooperative Research Centre, 2020). A typical composition of HPMSM is shown in Table 10. Table 10. Product specification for battery grade manganese sulfate (adapted from Future Battery Industries Cooperative Research Centre, 2020). Element Specification Mn (%) 31.8 Pb (ppm) 10 As (ppm) 10 Cd (ppm) 10 Ca (ppm) 50 Mg (ppm) 50 Na (ppm) 50 Fe (ppm) 10 Zn (ppm) 10 Cu (ppm) 10 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 82 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance A hydrometallurgical processing flow sheet used in the production of HPMSM or high-purity electrolytic manganese metal (HPEMM) from manganese oxide ores is shown Figure 11. The process is currently practiced commercially at the Manganese Metal Company in South Africa (Manganese Metal Company (Pty) Ltd, 2022). HPMSM can be directly produced using oxide or carbonate ores of manganese. A reductive leaching or calcination step is necessary for oxide ores. This step lowers the oxidation state of manganese to Mn2+, which is amenable to acid dissolution. Subsequent steps include iron oxide precipitation and solution purification steps. The flowsheet is capable of producing HPEMM or HPMSM depending on the marketing demand (Manganese Metal Company (Pty) Ltd, 2022). Figure 11. Hydrometallurgical flowsheet used in the production of high-purity electrolytic manganese metal (adapted from Manganese Metal Company (Pty) Ltd, 2022). Potential Applications to Minnesota Resources The pursuit of higher battery energy density and the use of costly raw materials such as cobalt have pushed the battery industry to select cathodes with lower cobalt content. Manganese sulfate is therefore used to replace part of the cobalt content in NCM batteries to reduce manufacturing costs (Li, et al., 2020). Historical laboratory studies on manganese ores from the Emily Manganese Deposit have NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 83 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance demonstrated the feasibility of producing electrolytic manganese metal and electrolytic manganese dioxide (Cooperative Mineral Resources, 2020). Because manganese sulfate monohydrate (HPMSM) is a preferred feedstock of lithium-ion battery manufacturers, future research could focus on evaluating the feasibility of producing HPMSM directly from the manganese oxide deposits from the Cuyuna District of central Minnesota. B.1.4. Direct Nickel Process (DNi-Process) Altilium, a British-based startup, is commercializing an alternative to the conventional high-pressure acid leaching (HPAL) process (Figure 12). Their technology allows for the extraction of nickel from laterite ores at atmospheric pressure and at low temperature. The process is capable of generating mixed hydroxide precipitates (MHP), which is the preferred feed material for nickel sulfate manufacturers. The process also allows for the recycling of 95% of the nitric acid used to extract the metals. Furthermore, the process produces a nitrogen-rich inert residue that can be dry stacked and returned to the mine to encourage the growth of local flora. The flowsheet is capable of generating other byproducts such as hematite, magnesium oxide, aluminum hydroxide, and scandium oxide (Robinson, et al., 2017; Altilium Group Ltd, 2021). Figure 12. Process flowsheet for Direct Nickel Process (adapted from Altilium Group Ltd, 2021). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 84 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Potential Applications to Minnesota Resources Historical metallurgical test work on Duluth Complex Cu-Ni-PGE mineralization has shown low nickel and cobalt recoveries from non-sulfide minerals (Polymet Mining Inc., 2007). The laboratory studies indicate a loss of about 25-35% of nickel while concentrating sulfides. The unrecoverable nickel occurs as magnesium-iron-nickel silicate that is tied up in the mineral olivine. Mineralogical studies on the NorthMet deposit indicate that approximately 25-35% of the rock is composed of olivine, which contains an average of about 0.1% Ni (Polymet Mining Inc., 2007). Future research could focus on using the Direct Nickel process to recover nickel and cobalt that is tied up in the mineral olivine. The benefits of this approach include: ● Allows the conversion of nickel in olivine-rich tailings to battery-grade materials, ● Potential recoveries of nickel and cobalt offers additional revenue streams, and ● Provides a method to recover metals from waste tailings. B.1.5. Hydro-to-Cathode Technology Founded in 2015 as a spinout from the lab of Prof. Yan Wang at Worcester Polytechnic Institute (WPI), Hydro-to-Cathode technology converts mixed streams of lithium-ion batteries, regardless of their chemistry, into various nickel manganese cobalt (NMC)-based cathode active materials (Sa, et al., 2016). Instead of extracting and separating the metals out individually like conventional hydrometallurgical technologies and then reintegrating into battery materials, Hydro-to-Cathode goes directly from the leaching and dissolution processes into battery material production, thereby avoiding the individual extraction of the reclaimed metals (Zou, et al., 2013; Zheng, et al., 2018) and enabling direct use of these materials in making new batteries. Massachusetts-based Ascend Elements plans to scale-up the technology by 2023. Ascend Elements states that the technology enables 35% reduction in cost, 32% reduction in emissions, and 13% reduction in energy consumption to produce NMC active materials compared to the production of virgin cathodes (Ascend Elements, 2021). Potential Applications to Minnesota Resources This technology offers a possibility of recovering cathode active materials from the end-of-life batteries collected from various sources in Minnesota. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 85 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 13. Flowsheets comparing Hydro-to-Cathode™ with traditional hydrometallurgical and pyrometallurgical treatment of end-of-life batteries (adapted from Ascend Elements, 2021). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 86 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance B.1.6. Li-Cycle Li-Cycle is a Canadian based startup that has developed a proprietary "Spoke and Hub" recycling technology to process battery manufacturing scrap and end-of-life batteries (Li-Cycle, 2021). The process flowsheet (Figure 14) employs a shredding process, which converts the used battery into a black mass containing lithium, cobalt, nickel, and other metals. This black mass is further processed using a proprietary hydrometallurgical process that transforms it into various battery grade materials. Potential Applications to Minnesota Resources This technology offers a possibility of recovering cathode precursors from the end-of-life batteries collected from various sources in Minnesota. B.1.7. Iron Salt Technology and Vanadium Redox Flow Technology VoltStorage, a Munich-based startup, is a provider of smart solar storage systems based on Iron Salt Technology (and Vanadium Redox Flow Technology), which is designed to make renewable energy available 24/7. The advantages of an iron (or vanadium) electrolyte consist largely in using pure water with the device, which makes it non-flammable in the event of extreme environmental conditions or malfunctions. In addition, iron can be 100% recycled, and is available in large quantities in Minnesota, and worldwide. The vanadium used in the storage medium is a byproduct of iron production (VoltStorage GmbH, 2021). B.1.8. Mitra Chem Technologies -Lithium Iron Phosphate Batteries Today, 100% of industrialized iron-based cathode manufacturing capacity is in China. Mitra Chem, a Silicon Valley startup, aims to boost the North American battery supply chain by producing an iron- based cathode for the Western mass-market EV industry. Mitra Chem states that its iron-based cathode moves away from the use of elements such as nickel and cobalt due to price volatility and known supply- chain ethics issues. Mitra Chem also asserts that its approach can shorten the lab-to-production timeline by >90% by allowing the invention of new battery chemistries (Palihapitiya, 2021; Alamalhodaei, 2021). Mitra Chem is currently building a R&D facility in Mountain View, California, with the aim of producing pre-pilot iron-based cathodes by mid-2022 (Mitra Chem Technologies, 2021). Potential Applications to Minnesota Resources Hydrometallurgical processes offer a possibility of producing iron and vanadium compounds that are suitable for energy storage systems. Future research efforts could focus on evaluating the feasibility of producing such compounds from Minnesota’s Cu-Ni-Co-PGE, Fe-Ti-V deposits, and Fe and Mn-Fe deposits. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 87 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 14. Hydrometallurgical process used by Li-Cycle for the treatment of end-of-life batteries (adapted from Li-Cycle, 2021). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 88 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance B.2. Critical Metal Extraction from Low-Grade Ores and Waste Tailings B.2.1. Lilac Solutions Lilac Solutions, a startup in Oakland, California, has developed a new ion exchange technology to extract lithium from brines without the need for evaporation ponds (Lilac Solutions, 2021). In the Lilac Solutions process, proprietary beads are loaded into columns, brine flows through the columns, and the beads absorb lithium. Hydrochloric acid is used to flush out the lithium, yielding lithium chloride. Further processing converts lithium chloride into lithium carbonate or lithium hydroxide, which is sold to battery manufacturers. Potential Applications to Minnesota Resources This technology could potentially facilitate the recovery of lithium from end-of-life batteries in Minnesota. B.2.2. Jetti Resources Jetti Resources, in partnership with the University of British Columbia, has developed a catalytic technology that allows leaching of copper from low-grade primary sulfides at atmospheric temperature and pressure (Figure 15). The catalyst (thiourea – an organosulfur compound having a thiocarbonyl functional group) negates the detrimental passivation layer that usually forms on chalcopyrite during oxidative heap leaching. Ferric ions, which are responsible for the breakdown of chalcopyrite, also promote its passivation by enabling the formation of copper deficient iron-sulfur layers (Dixon, et al., 2019). UBC researchers postulate that the proprietary catalyst facilitates the disruption of sulfur metal bond of the mineral, allowing copper extraction to take place while regulating the effects of the ferric ions that contribute to the passivation layer (Dixon, et al., 2019). Currently, the low-grade copper ores may not be economical for bioleaching methods and are often disposed of as waste. The catalytic technology integrates with existing heap leaching methods and downstream processing operations to extract copper from primary sulfides (Rebolledo, et al., 2019). Figure 15. Process flowsheet for Jetti Process (adapted from Dixon, et al., 2019). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 89 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Potential Applications to Minnesota Resources Historical recovery attempts have focused on producing smelter-grade copper concentrates from Minnesota’s Cu-Ni-Co-PGE mineralization (Black, et al., 2018; Mayhew, et al., 2009; Talon Metals Corp, 2021). Some stakeholders believe that the shipment of concentrates to international markets is not sustainable due to fluctuating demand and supply for copper metal. Therefore, further technical evaluation is necessary to determine the feasibility of using the Jetti Process for the recovery of copper metal. The benefits of such an approach include: ● Offers a potential alternative route to smelting and pressure oxidative leaching process, which requires large capital investment, thus making it difficult for new players to enter the market, ● Allows the production of copper metal in the state of Minnesota, and thereby ● Enhancing the royalty value of minerals owned by the State. B.2.3 Phoenix Tailings Phoenix Tailings is a University of Connecticut-affiliated startup that is working to build a solution that could not only clean up legacy tailings ponds but could also turn the waste materials they hold into valuable, usable products (Small Business Innovation Research (SBIR), 2020; Severance, 2020). Potential Applications to Minnesota Resources Due to the proprietary nature of the above technology, a detailed description of this process is not publicly available. Phoenix Tailings website indicates that their re-mining technology is capable of recovering rare earth elements like cerium, lanthanum, neodymium, samarium, and scandium from waste tailings. B.2.4. Nth Cycle Nth Cycle is a Boston-based startup that has developed an electro-extraction technology that extracts critical metals from batteries, e-waste, low-grade ore, and mine tailings so they can be reused to make new clean energy products (Nth Cycle, 2021). Potential Applications to Minnesota Resources Due to the proprietary nature of the above technology, a detailed description of this process is not publicly available. Nth Cycle’s website indicates that their electro-extraction technology is capable of recovering critical metals from batteries, e-waste, low-grade ore, and mine tailings. B.3. Carbon Mineralization Technologies B.3.1. Carbfix Carbfix is an Icelandic startup that has developed a technology that attempts to permanently sequester CO2 in underground geological formations. The technology dissolves CO₂ in water and then injects the solution into the ground, where it interacts with reactive rocks (basalt) to form mineral carbonates. These efforts culminate a decade of lab and field research that explored various aspects of water-rock- CO2 interaction. The research used laboratory and pilot scale pressure reactors to study the impact of mineralogy, water chemistry, time, temperature, pressure, and pH on 1) dissolution rates of CO2 into aqueous phase, 2) release rates of cations from CO2 reactive rocks, 3) precipitation of carbonate minerals, and 4) co-precipitation of other minerals. The data from these studies were used for reaction path modeling studies to predict the basalt-CO2-water interaction prior to the field pilot study and to characterize prospective geological formations suitable for CO2 injection (Snæbjörnsdóttir, et al., 2020). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 90 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Potential Applications to Minnesota Resources To support federal government endeavors to define conditions under which mineral carbonation processes could remove 10 GtCO2 per year by 2050, NRRI could conduct geological resource assessment and characterization of mafic and ultramafic rocks in Minnesota. This will require mapping of local geologic resources and detailed spatial, mineralogical, lithogeochemical, and mineral chemical characterization to assess their potential for large-scale in-situ carbon mineralization like the Carbfix Project. B.4. Mercury and Selenium Removal Technologies B.4.1. Sulfur based sorbents Professor Justin Chalker at the Flinders University, Australia has synthesized a low-cost mercury- capturing polymer synthesized entirely from waste material (Worthington, et al., 2017). The research at Chalker’s Lab demonstrated the effectiveness of sorbents in capturing common forms of mercury pollution, including liquid mercury metal, mercury vapor, and inorganic mercury and organomercury compounds. Further, the research indicates that neither the polymer nor the mercury-bound polymer is toxic to human cells. Research is currently underway to develop applications for in situ remediation of mine tailings, soil, and agricultural wastewater (Worthington, et al., 2017). B.4.2. Tusaar Corp The University of Colorado has developed a biosorbent to remove lead, mercury, uranium, and other toxic metals from water and the environment (Carlson, et al., 2020). Tusaar Corp has licensed the technology from University of Colorado. The U.S. National Science Foundation and the U.S. Department of Energy (Tusaar Corp, 2022) funded the research. B.4.3 Zero Valent Iron (ZVI) technology ZVI reduces selenium oxyanions to elemental selenium. Ferrous cations can also reduce selenate to selenite and subsequently remove selenite by adsorption to iron hydroxides (Regenesis, 2022). B.4.4. Advanced Biological Metals (ABMet) technology This technology uses special strains of common nonpathogenic microbes that facilitate the precipitation of soluble selenium into elemental selenium. ABMet systems find applications in jurisdictions that require low effluent selenium concentrations by current or future regulations (Suez Water Technologies and Solutions, 2022). B.4.5. Saturated Rock Fill (SRF) Technology Enviromin, Inc. in cooperation with Center for Biofilm Engineering (CBE) at the Montana State University and Teck Resources Limited has developed the Saturated Rock Fill for in-situ reduction of selenium from mine drainage. Waste rocks from certain mineral resources can release toxic concentrations of selenium into water upon exposure to air and water. The technology utilizes a biological reduction of oxidized selenium (Se (VI)) to less mobile (Se (0)) forms within the mine waste rock (Kirk, et al., 2017). B.4.6. Membrion Technologies Membrion Technologies is a Seattle-based startup that has developed a ceramic ion exchange membrane for removing salt and heavy metals from wastewater. While membrane fouling and poor chemical durability are among the limitations of traditional polymer membrane on the market today, Membrion's ceramic membranes resist fouling, have no lower pH limit, and can handle harsh oxidizers present in many wastewaters (University of Washington, 2021). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 91 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Potential Applications to Minnesota Resources The Fond du Lac Band is concerned that existing mercury impairments will make the cumulative effects of mercury from new or expanded discharges greater (Fong, 2022). Therefore, the Band is proposing that future discharges to impaired waters must meet the Fond du Lac Band’s human health chronic mercury standard of 0.77 ng/L (Fong, 2022). Future research programs could evaluate feasibility of using mercury-capturing sorbents to lower the mercury concentrations from potential discharges. B.5. Demonstrated Hydrometallurgical Technologies for Regional Mineral Resources The technologies in this category have been demonstrated at bench and/or pilot scale for various mineral resources in Minnesota. Examples of these technologies include CESL, PLATSOL™, Albion Process™, and Mixed Hydrochloride processes. Following is a brief description of each of these technologies. B.5.1. Cominco Engineering Services Limited (CESL) CESL has developed a hydrometallurgical process for treating copper and nickel sulfide concentrates, including bulk concentrates from Teck Resources Mesaba Cu-Ni Project, located approximately 5 miles south of Babbitt, MN. The deposit contains a geologic resource in excess of 1 billion metric tons grading approximately 0.43% Cu and 0.09% Ni with minor Co and PGM values (Mayhew, et al., 2009). Figure 16 shows the proposed flowsheet for the Mesaba CESL Refinery. Table 11 shows the product quality of mixed hydroxide precipitate that was produced using the proposed flowsheet. The CESL Process is composed of the following steps (Mayhew, et al., 2009): ● Light regrinding of the concentrate is necessary to increase the surface area of the particles, which improves the leaching kinetics in an autoclave. ● The leaching process is composed of two stages: 1) The first stage involves oxidation of sulfide concentrates at medium temperatures (150° C) and elevated pressure (200 psi) in the presence of chloride ions (12 g/L). The sulfide minerals are oxidized in the autoclave to form basic metal sulfate, hematite, and elemental sulfur. The chloride ion is added to accelerate the leach kinetics and minimizes the sulfur oxidation to sulfate, thereby allowing for economic recovery of metals from a bulk concentrate. The autoclave discharge is then thickened and filtered. The filtrate is recycled back to the autoclave, while the filter cake residue is sent to an atmospheric leach reactor; 2) In the second stage, an atmospheric leach, the filter cake residue is dissolved under mild acid conditions at atmospheric temperature and pressure. ● The pregnant leach solution from the atmospheric leach step is sent to the copper solvent extraction circuit for selective copper recovery using an organic mixture of 40% v/v extractant (LIX 973N®) and 60% v/v kerosene diluent (conosol 170E). ● The pregnant electrolyte from the solvent extraction process is sent to a conventional electrowinning circuit to produce Grade A copper cathode (99.999% Cu). ● The raffinate from copper solvent extraction process is fed to the nickel recovery circuit. ● The nickel recovery circuit consists of three steps: 1) iron and aluminum removal step via two step precipitation, 2) zinc, copper, and cadmium are precipitated as sulfides using H2S gas, and 3) nickel/cobalt precipitation with the addition of calcined magnesia. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 92 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance ● Key metallurgical results from the Mesaba pilot campaign are as follows: ○ copper extraction was 95% ○ nickel extraction was 95% ○ cobalt extraction was 97% ○ sulfide oxidation was 6.9% ● The chemical composition of mixed hydroxide precipitate is shown in Table 11. Table 11. Mixed hydroxide precipitate generated from the Mesaba pilot campaign (adapted from Mayhew, et al., 2009). Ni (%) Co (%) Mg (%) Ca (%) Cu (%) Fe (%) Mn (%) Zn (%) 46.0 2.0 0.8 0.6 0.02 0.1 0.68 0.02 NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 93 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 16. CESL hydrometallurgical flowsheet developed for the Mesaba deposit (Source: adapted from Mayhew, et al., 2009). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 94 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance B.5.2. PLATSOL™ The PLATSOL™ process was developed to process polymetallic sulfide concentrate containing copper, nickel, cobalt, platinum, palladium, gold, and silver (Black, et al., 2018). Polymet Mining Inc. intends to use the PLATSOL™ process to treat flotation concentrates from the NorthMet deposit (Black, et al., 2018). The total proven and probable mineral reserves for the NorthMet Deposit are estimated to be 254.669 million tons at an equivalent copper grade of 0.586% (Black et al., 2018). The majority of the metals of interest are concentrated in chalcopyrite, cubanite, pentlandite, and pyrrhotite. Platinum, palladium, and gold are found in bismuthides, tellurides, and alloys (Black, et al., 2018). Figure 17 shows a flowsheet for the PLATSOL™ process for the proposed NorthMet Project. The PLATSOL™ process is composed of the following steps (Black, et al., 2018): ● The process uses chloride-assisted total pressure oxidation to extract base- and precious metals into the autoclave (pressurized vessel operated at high temperature) solution. The process is completed at high oxygen over pressure (110 psi) and high temperatures (225° C) with additions of 5–20 g/L NaCl to promote PGM minerals dissolution. Under the above conditions, base metals (Cu, Ni) and precious metals (gold (Au), platinum (Pt), and palladium (Pd)) are co- dissolved in a single step. The autoclave oxidation process converts sulfide minerals into metal sulfates, and iron minerals primarily into hematite, while the precious metals are converted to chloro-complexes. The leach residue consists of iron precipitates, unreacted gangue (non-ore minerals), and minor amounts of residual base and precious metal minerals. ● After the autoclave leaching, the solids are separated from the leach solution and washed. The leftover residues are then sent to waste disposal while the leach solution advances to metal recovery. ● The recovery of Au, Pt, and Pd from the autoclave solution is accomplished by precipitation with CuS. The CuS is less noble compared to Au, PdS, and PtS; hence, the PGMs in solution precipitate in exchange for Cu going into solution. ● In the subsequent step, PGM filtrate is mixed with copper sulfide concentrate resulting in an enriching copper grade. ● Residual soluble copper present in the depleted liquor from the copper enrichment stage is precipitated with NaHS. ● The Cu-NaHS filtrate streams are then subjected to a Fe/Al removal stage. In this stage, Fe/Al is precipitated by adding lime and oxygen. As this occurs, iron is oxidized from the ferrous to the ferric state with oxygen or air with limestone addition for neutralization and pH control. ● The filtrate from the Fe/Al stage is treated with magnesia (MgO) to precipitate mixed cobalt and nickel hydroxide. ● The filtrate from the first mixed hydroxide precipitation stage is treated with hydrated lime to further recover additional nickel and cobalt precipitates. ● Finally, to control the build-up of magnesium in solution, a magnesium removal step (with lime) is introduced into the circuit. Magnesium sulfate reacts with lime to form magnesium hydroxide and gypsum. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 95 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 17. PLATSOL™ hydrometallurgical flowsheet developed for the NorthMet Project (adapted from Black, et al., 2018). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 96 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance B.5.3. Albion Process™ The Albion Process™ was developed by Glencore to treat refractory precious metal and base metal concentrates that are unsuitable for toll smelting (Glencore Technology, 2020). The process employs ultrafine grinding of concentrates in an IsaMill™ prior to an atmospheric leaching process. Fine grinding increases the surface area and prevents the passivation of minerals during leaching reactions. Passivation generally occurs by precipitation of iron oxides and/or elemental sulfur on the mineral surface. These precipitates prevent the access of oxidants to the mineral surface, thereby preventing the dissolution reactions. The finely ground concentrate is then fed to a stainless steel reactor fitted with HyperSparge™ supersonic oxygen injectors to maximize oxygen mass transfer and facilitate the oxidation reactions. The process runs at atmospheric pressure and temperature and under mildly acidic conditions. The leach liquor is then directed to metal recovery circuits that use conventional technologies to produce the desired saleable products (Glencore Technology, 2020). Figure 18 shows a simplified flowsheet for the Albion Process™. Figure 18. General schematic for the Albion Process™ (Source: adapted from Glencore Technology, 2020). Table 12 compares the three hydrometallurgical extraction methods that have been demonstrated for Minnesota’s mineral resources. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 97 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 12. Comparison of CESL, PLATSOL™, and Albion Process™. Process Lixiviant P80 grind size, µm Leaching temperature °C Pressure (psi) Unique feature Sulfur product Leaching time, hours Maturity Stage as of June 2022 Reference CESL Sulfate + Chloride 15-40 150 200 10-15 g/L Cl - Sulfur 1-2 Final feasibility (Mayhew, et al., 2009) PLATSOL™ Sulfate + Chloride 15 <220 110 5-20 g/L Cl - Sulfate 1-2 Final feasibility (Black, et al., 2018) Albion Process™ Sulfate 10-15 85-90 Atmosphere O2 injected at 450–550 m/s Sulfur 22 Commercial (Glencore Technology, 2020) NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 98 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix C: Existing Hydrometallurgical Technologies Appendix C provides a brief summary of existing hydrometallurgical technologies that are industrially practiced to extract copper, nickel, cobalt, gold, platinum group elements, titanium dioxide, manganese, lead, and zinc. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 99 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance C.1. Commercial Plant Operations in North America In addition to identifying key research facilities, the study identified key industrial facilities where hydrometallurgical techniques are commercially practiced for the extraction of non-ferrous metals like copper, nickel, cobalt, gold, platinum group elements, titanium dioxide, manganese, lead, and zinc. Figure 19 shows the location of these metallurgical complexes and Table 13 provides a comprehensive list of commercial operations in North America. In some instances, hydrometallurgical techniques are exclusively used for the extraction of metals. Examples include Freeport McMoran’s Morenci facility in Arizona (Figure 20), Vale’s Long Harbor facility in Newfoundland (Figure 21), and Terrafame’s Sotkamo facility in Finland (Figure 22). In other instances, they are used to upgrade the pyrometallurgical smelter and converter products. Examples include Glencore’s Nikkelverk facility in Norway (Figure 23), Sibanye-Stillwater’s facilities in Rustenburg, South Africa (Figure 24) and Stillwater, Montana (Figure 27), and Rio Tinto Iron and Titanium’s QIT facility in Quebec, Canada (Figure 25). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 100 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 19. A map of commercial non-ferrous metallurgical operations in North America. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 101 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 13. A list of non-ferrous metallurgical extraction facilities in North America. Company Name Location Type of Plant Products Pyrometallurgy Hydrometallurgy/Electrometallurgy Stillwater Sibanye Stillwater, MT PGM Refinery PGM concentrate, nickel sulfate, copper cathode EAF smelting, Kaldo converter Nickel atmospheric leach, nickel sulfate crystallization, copper-PGM pressure leach, copper electrowinning, selenium/tellurium precipitation. Johnson Matthey West Deptford, NJ PGM Refinery Gold, iridium, platinum, palladium, rhenium, rhodium, ruthenium, silver Reverberatory furnace HCl/Cl2 pressure leaching, solvent extraction, precipitation, reduction using hydrazine Freeport McMoran Morenci, AZ Copper SX- EW Copper cathode, molybdenum concentrate Smelting ceased in 1984 MT Pressure concentrate leaching and ROM bio heap leaching-SX-EW Baghdad, AZ Copper SX- EW Copper cathode, molybdenum concentrate Not used HT Pressure concentrate leaching and ROM heap leaching-SX-EW Sierrita, AZ Copper SX- EW Copper cathode, molybdenum, rhenium Molybdenum roasters Heap leaching-SX-EW Miami, AZ Copper Smelter and Copper SX-EW Copper cathode, precious metals IsaSmelt™ technology (primary furnace) and ELKEM electric furnace (secondary); four Hoboken style converters Heap leaching-SX-EW Safford, AZ Copper SX- EW Copper cathode Not used Heap leaching-SX-EW NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 102 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Company Name Location Type of Plant Products Pyrometallurgy Hydrometallurgy/Electrometallurgy Chino, NM Copper SX- EW Copper cathode, molybdenum Smelter ceased in 2005 Heap leaching-SX-EW Tyrone, NM Copper SX- EW Copper cathode Not used Heap leaching-SX-EW El Paso, TX Copper and Precious Metal Refinery Copper cathode, silver, gold, PGE, tellurium, selenium Not used Electrorefining, copper pressure leach, ferric chloride leach of silver, HCl leach of gold/PGE, solvent extraction of silver and gold, Rio Tinto Kennecott Magna, UT Copper Smelter and Refinery Copper cathode, gold, silver, molybdenum oxide, rhenium, selenium, tellurium Smelting (The smelter at Kennecott captures 99.9 percent of the sulfur in the feed, making it one of the cleanest in the world) Electrorefining (99.999 percent pure copper); rhenium via ion exchange; chlorination process to recover gold, silver, lead, and selenium. ASARCO Hayden, AZ Copper Smelter Copper cathode, sulfuric acid Smelting/converting (oxygen flash smelting furnace, Anode Furnace) - Ray, AZ Copper SX- EW Copper Not used Heap leaching-SX-EW Silver Bell, AZ Copper SX- EW Copper Not used Heap leaching-SX-EW Amarillo Copper Refinery, TX Copper and Precious Metal Refinery Copper, silver, gold, platinum, palladium, antimony, nickel sulfide, selenium, and tellurium Not used Electrorefining, Hydrometallurgy to recover precious metals NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 103 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Company Name Location Type of Plant Products Pyrometallurgy Hydrometallurgy/Electrometallurgy KHGM Carlota Mine, AZ Copper SX- EW Copper cathode Not used Heap leaching, SX-EW Hecla Mining Fire Creek, NV Gold Gold dore Smelting gold bearing conc. from hydromet circuit Cyanide leaching, Carbon in Leach, Merrill Crowe Precipitation Newmont Corporation Cripple Creek & Victor, CO, USA Gold Gold dore Smelting gold bearing conc. from hydromet circuit Heap leaching-EW Cortez, NV Gold Gold dore Smelting gold bearing conc. from hydromet circuit Heap Leaching, Cyanide leaching, Carbon in Leach, Electrowinning Carlin, NV Gold Gold dore Smelting and Roasting Heap Leaching, Autoclaves, Cyanide leaching, Carbon in Leach, Electrowinning Turquoise Ridge, NV Gold Gold dore Smelting gold bearing conc. from hydromet circuit Heap Leaching, Autoclaves, Cyanide leaching, Carbon in Leach, Electrowinning Phoenix, NV Gold- copper Gold dore, copper Smelting gold bearing conc. from hydromet circuit gold from cyanide leaching; a copper from heap leach pad and a solvent extraction electrowinning (“SX/EW”) plant Long Canyon, NV Gold Gold dore Smelting gold bearing conc. from hydromet circuit Heap leaching Kinross Gold Fort Knox, AK Gold Gold dore Smelting gold bearing conc. from hydromet circuit Run-of-mine valley-fill cyanide heap leaching, agitated cyanide leaching, and a carbon-in pulp (CIP) circuit;, EW Round Mountain, NV Gold Gold dore Smelting gold bearing conc. from hydromet circuit Heap leach, Carbon in Column, EW NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 104 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Company Name Location Type of Plant Products Pyrometallurgy Hydrometallurgy/Electrometallurgy Bald Mountain, NV Gold Gold dore Smelting gold bearing conc. from hydromet circuit Heap leach, EW Glencore Sudbury Integrated Nickel Operations (Sudbury INO), ON Nickel Smelter nickel, copper and cobalt in matte, sulfuric acid Roaster, electric arc furnace smelting, converter Flotation to recover copper from slag Horne Copper Smelter, Rouyn- Noranda, Quebec Copper Smelter and Converter Copper anodes, sulfuric acid Smelter, converter, anode furnace Flotation to recover copper from slag Canadian Copper Refinery, Quebec Copper and Precious Metal Refinery Copper cathodes, gold, silver and other specialty metals and chemicals, including selenium, tellurium dioxide, nickel sulfate and a concentrate of platinum group metals Not used Electrorefining copper, anode slimes treated via hydrometallurgy to recover PGMs, nickel sulfate, selenium, tellurium dioxide, gold, and silver Vale Long Harbor, Nova Scotia Nickel, Copper, and Cobalt Refinery Nickel, copper, cobalt Not used Pressure oxidation leaching, copper solvent extraction, cobalt solvent extraction, copper & cobalt & nickel electrowinning NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 105 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Company Name Location Type of Plant Products Pyrometallurgy Hydrometallurgy/Electrometallurgy Copper Cliff Nickel Refinery, Sudbury Nickel Smelter and Copper Refinery Nickel, nickel oxide, copper, anode slimes from electrorefining copper, carbonyl residue Bulk smelting, Nickel refining (carbonyl process), Ni Matte Roasting to NiO Electrorefining Copper Sherritt International Corp. Fort Saskatchewan, Saskatchewan Nickel Refinery High purity nickel and cobalt powder and briquettes Sintering nickel and cobalt products High-pressure ammoniacal leaching; high pressure hydrogen reduction; precipitation Teck Resources Trail, British Columbia Zinc and Lead Smelter and Refinery Refined zinc and lead, germanium, indium, and cadmium Roasting, melting/casting of Zn; flash smelting of Pb; slag-fuming furnace; Pressure leaching plant, cementation, electrowinning, vacuum distillation, oxide leaching Honeywell Electronic Materials SLC, UT Titanium Metal Titanium metal sponge Refining (electrode vacuum arc furnace) Hunter process (sodium reduction) Allegheny Technologies Inc. Rowley, UT Titanium Metal Titanium metal sponge Refining (electrode vacuum arc furnace) Kroll process (Magnesium reduction) Titanium Metals Corp. (TIMET) Henderson, NV Titanium Metal Titanium metal sponge Refining (electrode vacuum arc furnace) Kroll process (Magnesium reduction) Chemours DeLisle, MS; Titanium Dioxide TiO2 pigment Chlorination process, fractional distillation Not used New Johnsonville, TN Titanium Dioxide TiO2 pigment Chlorination process, fractional distillation Not used NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 106 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Company Name Location Type of Plant Products Pyrometallurgy Hydrometallurgy/Electrometallurgy Tronox Hamilton, MS Titanium Dioxide TiO2 pigment Chlorination process, fractional distillation Not used INEOS Ashtabula, OH Titanium Dioxide TiO2 pigment Chlorination process, fractional distillation Not used Venator Corp Lake Charles, LA Titanium Dioxide TiO2 pigment Chlorination process, fractional distillation Not used Rio Tinto Iron and Titanium Sorel-Tracy, QC Titania Slag Upgraded TiO2 slag, high purity pig iron, iron powders EAF smelting, roasters High pressure/autoclave-HCl leaching Nyrstar Clarksville, TN Zinc Smelter and Refinery Special high grade (SHG) zinc, zinc alloys and sulfuric acid, germanium concentrate, leach products, zinc sulfate, copper sulfate, cadmium metal Roasting and casting Atmospheric sulfate leaching, precipitation, electrowinning Doe Run Viburnum, MO Lead Smelter and Refinery Refined lead Blast furnace smelting and casting Stable fluoboric acid leaching, electrowinning Gopher Resource Eagan, MN Lead Smelter and Refinery Recycled pure lead, antimonial and calcium lead alloys Blast furnace smelting and casting Not used Baltimore, MD Manganese Proprietary technologies NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 107 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Company Name Location Type of Plant Products Pyrometallurgy Hydrometallurgy/Electrometallurgy Prince International Corporation (Vibrantz Technologies) Houston, TX Manganese Manganese chemicals (EMD, MnO, MnCl2, MnSO4, Mn(NO3)2, MnCO3), Iron oxides Proprietary technologies Mount Dora, FL Manganese New Johnsonville, TN Manganese New Castle, DE Manganese Quincy, IL Manganese Milwaukee, WI Manganese Energizer Holdings, Inc. Asheboro, NC Manganese Batteries using many technologies including lithium, alkaline, carbon zinc, nickel metal hydride, zinc air, and silver oxide Proprietary technologies Proprietary technologies Garrettsville, OH Manganese Westlake, OH Manganese Marietta, OH Manganese Dayton, OH Manganese Fennimore, WI Manganese Portage, WI Manganese Felman Production, LLC Letart, WV Manganese Ferro silicomanganese, Ferromanganese Submerged arc furnaces Not used NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 108 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 20. Medium-temperature pressure oxidation process practiced at Freeport McMoran's Morenci facility, AZ, USA (Source: Green, et al., 2018). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 109 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 21. Pressure oxidation leaching process practiced at Voisey's Bay Long Harbor facility (Source: Wheaton Precious Metal, 2018). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 110 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 22. Biological leaching process practices at Terrafame in Sotkamo, Finland (Source: Pitkäjärvi, 2011). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 111 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 23. Chloride-based autoclave pressure leaching practiced at Glencore’s Nikkelverk, Kristiansand in Norway (Source: Crundwell, et al., 2011). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 112 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 24. Hydrometallurgical flowsheet used in the extraction of platinum group elements at Rustenburg, South Africa (Source: Crundwell, et al., 2011). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 113 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 25. Hydrometallurgical process used in the production of high-purity titanium dioxide slag in Quebec, Canada (Source: Guéguin & Cardarelli, 2007). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 114 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 26. Hydrometallurgical process flowsheet used in the production of electrolytic manganese metal in China (Source: Duan, et al., 2011). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 115 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 27. Hydrometallurgical flowsheet practiced at Sibanye Stillwater Complex in Montana, USA (Source: Sibanye-Stillwater, 2018). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 116 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix D: Mineral Resources of Minnesota Appendix D provides a brief and generalized descriptions of mineral and waste resource of Minnesota. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 117 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance D.1. Mineral Resources of Minnesota Three general mineral resources categories that have potential hydrometallurgical applications have been identified for this project. These categories include: 1) non-ferrous resources, which include Cu-Ni- Co-PGE and Ti-V deposits, 2) ferrous resources, which include Fe and Mn-Fe deposits, and 3) aggregate and byproduct resources. Brief and generalized descriptions of these resource categories are presented in the following section of this report. D.1.1. Non-ferrous Resources The non-ferrous mineral resources consist of mafic magmatic mineral systems outlined in recent USGS publications (Schulz, et al., 2017 and Hofstra and Kreiner, 2020), including: 1) Contact-type Ni-Cu-PGE sulfide deposits, 2) Conduit-type Ni-Cu-PGE sulfide deposits, and 3) Iron-Titanium oxide (Fe-Ti-V-P) deposits (Figure 28). D.1.1.1. Contact-type Cu-Ni-Co-PGE sulfide deposits Contact-type Cu-Ni-PGE magmatic sulfide deposits (Zientek, 2012) of the midcontinent of North America are exemplified by the large, mainly disseminated sulfide deposits that occur along the basal contact of the Duluth Complex where magmas intruded and incorporated footwall Paleoproterozoic Animikie Group metasedimentary rocks and Archean granitoids. Major deposits include Birch Lake, Maturi, Mesaba, NorthMet, Serpentine, and Spruce Road (Figure 29). Disseminated and local massive sulfide mineralization of the Duluth Complex was historically estimated to contain about 4.4 billion metric tons of ore with average grades of 0.66% Cu and 0.2% Ni at a 0.5% Cu cut-off (Listerud and Meinike, 1977). Recent exploration and project development has led to upgraded mineral resource estimates for many of these deposits (Table 14), resulting in a combined upgraded estimate of 9.57 billion metric tons with average grades of 0.406% Cu, 0.126% Ni, and 0.326 g/t Pt-Pd-Au. The Duluth Complex contact-type deposits typically contain interstitial disseminated sulfide minerals (pyrrhotite, chalcopyrite, cubanite, and pentlandite) at trace-to-10% of the mineralized rock by volume by visual estimate (Miller, et al., 2002). Mineralization can be extremely erratic in spatial extent and ore grades within basal units of the intrusions (Miller, et al., 2002). Thériault, et al. (2000) described mineralization in the basal section of the Partridge River intrusion as consisting of three distinct parts: 1) Cu-rich, PGE-poor disseminated sulfides, 2) Cu-rich, PGE-rich disseminated sulfides, and 3) semi- massive to massive sulfides. They interpreted these variations as resulting from systematic variations in magma inputs and flow regimes and accompanying sulfur contamination. Disseminated mineralization was a product of dispersed sulfides unable to coalesce because of disruption by multiple episodes of magma pulses along the basal contact (Miller, et al., 2002). Where mineralization is more consistently stratabound, such as in parts of the Maturi deposit in the South Kawishiwi intrusion, channelized magma flow was a likely organizing influence that also increased the metal content of transported sulfides (Peterson and Albers, 2007). Rare pyrrhotite-rich massive sulfide concentrations are spatially related to nearby sulfide-rich footwall rocks and/or fold structures (Hauck, et al., 1997). The Local Boy massive sulfide ore zone in the Babbitt deposit, Partridge River intrusion, has 5 to 25% Cu, 11 ppm Pd, and 8 ppm Pt, which are the highest PGE values reported for the Duluth Complex (Miller, et al., 2002). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 118 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 28. Location map of identified non-ferrous mineral resources in Minnesota. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 119 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 29. Bedrock geology and mineral resource location map of the contact-type deposits of the Duluth Complex and adjacent areas. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 120 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 14. Ni 43-101 compliant grade-tonnage estimates of mafic magmatic sulfide deposits associated with the Mid-Continent Rift. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 121 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance A critical component for development of contact-type sulfide deposits was the addition of country rock sulfur to mid-continent rift system mafic melts (see Ripley, 1981; Ripley and Al-Jassar, 1987; Arcuri, et al., 1998; Thériault, et al., 2000). Deposits in the Partridge River intrusion are clustered where pulses of metal-bearing mafic magma interacted with and incorporated footwall sulfur-bearing country rock (Ripley, 2013). A detailed study by Queffurus and Barnes (2014) suggest that sulfur contamination for a number of deposits resulted from in situ sulfide dissolution of sulfur-rich xenoliths of a pyrrhotite- bearing unit in the footwall Virginia Formation. D.1.1.2. Conduit-type Ni-Cu-PGE sulfide deposits Conduit-type Ni-Cu-PGE sulfide deposits are defined as magmatic sulfide mineralization restricted to small- to medium-sized mafic and/or ultramafic irregularly shaped tube-like intrusions or dikes that served as pathways for flow-through of picritic and/or Mg-rich basaltic magmas (Schulz, et al., 2014). These important sulfide deposits are unique in that they typically contain more metal and sulfur than could be derived from a magma volume equal to the limited volume of the small intrusions that host deposits. This implies that these deposits were products of a greater volume of magma than the current volume of the host intrusion. Thus, conduit-type sulfide deposits are the product of a large volume of magma that moved through open conduit systems, enriching an immiscible sulfide liquid with metals such as Ni, Cu, and PGE. Rocks that make up host intrusions generally do not represent primary magmas, but are accumulations of olivine, pyroxene, and immiscible sulfide liquid. Host rocks for Mid-Continent Rift conduit-type sulfide deposits with Ni>Cu are products of high MgO magmas that erupted only during the Plateau Stage of rift development (Nicholson, et al., 1997). The best documented conduit-type sulfide deposits within the Mid-Continent Rift include the Eagle deposit in northern Michigan (the only operating primary nickel mine in the US since production began in 2014), the Tamarack deposit in east-central Minnesota, and the Current Lake deposit in northern Ontario. The ultramafic Tamarack Intrusive Complex (see Figure 29 for location and Table 14 for grade- tonnage data), with a minimum intrusion age of 1105.6±1.2 Ma (Goldner, 2011), is made up of several distinct intrusive bodies, including an ovoid-shaped Bowl Intrusion of oxide gabbro and two sulfide mineralized intrusive dike-like peridotite bodies that give the complex a tadpole shape (Taranovic, et al., 2015) (Figure 30). Mineralization at Tamarack consists of disseminated to net textured to massive pyrrhotite, pentlandite, chalcopyrite, and minor cubanite (Taranovic, et al., 2015). Conduit-type sulfide deposits need country rock sulfur additions to magma to achieve sulfur saturation and formation of an immiscible sulfide liquid. Sulfur isotope data from the Eagle deposit (Ding, et al., 2012) and the Tamarack deposit (Taranovic, et al., 2018) are consistent with sulfur additions to ultramafic magmas from Paleoproterozoic metasedimentary country rocks and Archean basement rocks. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 122 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 30. Bedrock geologic map of the Tamarack Ni-Cu-Co-PGE conduit-type sulfide deposit. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 123 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance D.1.2. Ti-V Resources of the Duluth Complex Small titanium-iron±vanadium oxide-rich, plug-like, discordant intrusions along the southern basal section of the Duluth Complex are called Oxide-Ultramafic Intrusions, or OUIs. Rock types carrying the Ti-Fe±V oxide mineralization in OUIs include dunite, peridotite, and pyroxenite, typically with more than 10% semi-massive to massive oxide zones (Severson and Hauck, 1990). Deposits, including the major OUIs Longnose, TiTac, and Water Hen, can also carry minor Cu sulfide mineralization. Several OUIs are in faults or are close to fault zones, typically with nearby large inclusions of Biwabik Iron-formation (Hauck, et al., 1997). Such relationships suggested to Severson (1995) that there was a genetic connection between OUI Ti-Fe±V mineralization and inclusions of iron-formation, and further speculation that OUIs may have initially formed at depth and were injected upward along fault zones (Severson, 1995); alternately OUIs may have formed from a differentiated iron-rich melt that drained down into ultramafic cumulates along fault zones. Figure 31. Bedrock geologic and location map of Ti-Fe-V resources associated with cross-cutting oxide- ultramafic intrusions of the western Duluth Complex. Identified OUI-associated Ti-Fe-V deposits include the: 1) Longnose deposit, with a NI43-101 indicated resource of 58.1 million tons averaging 16.6% TiO2 (inferred 65.3 million tons averaging 16.4% TiO2) based on 27 drill holes and using a cutoff grade of 8% TiO2, 2) Titac deposit, with a NI43-101 inferred resource of 45.1 million tons averaging 14% TiO2 based on 32 drill holes and using a cutoff grade of 8% TiO2, and 3) Water Hen deposit, with a crudely estimated 62 million tons averaging 14% TiO2, based on 37 drill holes. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 124 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance D.1.3. Ferrous Resources Non-ferrous mineral resources consist of several categories of marine chemocline mineral systems outlined in recent USGS publications (Schulz, et al., 2017; Hofstra and Kreiner, 2020) including the Superior-iron deposits of the Mesabi Iron Range and iron-manganese deposits in the Cuyuna Iron Range (Figure 32). Figure 32. Location map of identified ferrous mineral resources in Minnesota. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 125 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance D.1.3.1. Superior Type Iron Resources of the Mesabi Iron Range Minnesota’s Superior type iron formations are exemplified by the Biwabik Iron Formation along the length of the Mesabi Iron Range (Figure 33), located primarily in St. Louis and Itasca counties. The Mesabi Iron Range is 120 miles long, averages one to two miles wide, and is comprised of rocks of the Paleoproterozoic Animikie Group, which consists of three conformable major formations: Pokegama Formation at the base, Biwabik Iron Formation in the middle, and the overlying Virginia Formation. These three formations display gentle dips to the southeast at an angle of 3-15 degrees. The Biwabik Iron Formation is subdivided into four informal members referred to as (from bottom to top): Lower Cherty, Lower Slaty, Upper Cherty, and Upper Slaty (Wolff, 1917), each of which are typically characterized by a granular (sand-sized) texture and thick-bedding (beds ≥ several inches thick). The slaty members are typically fine-grained (mud-sized) and thin-bedded (≤1 cm thick beds). Cherty members are largely composed of chert and iron oxides (with zones rich in iron silicate), while the slaty members are composed of iron silicates and iron carbonates with local chert beds. Both cherty and slaty iron-formation types are interlayered at all scales, but one type typically predominates in each of the four informal members, and they are so-named for this dominance Severson, et al. (2009). The Biwabik Iron Formation is around 175-300 feet thick in the extreme eastern end of the Mesabi Iron Range at Dunka Pit, 730-780 feet thick in the central Mesabi Iron Range/Virginia Horn area near Eveleth, around 500 feet thick in the western Mesabi Iron Range near Coleraine, and eventually exhibits a “nebulous ending about 15 miles southwest of Grand Rapids” (Marsden, et al., 1968) on the extreme western end of the Mesabi Iron Range. Leached and iron enriched direct ores (or natural ores) in the Mesabi Iron Range have been depleted and current mining focuses on taconite, a hard, non-oxidized ore typically containing 30-35% iron and 40-50% SiO2 (Morey, 1992) that is mined and processed using magnetic separation methods. Maps of currently active taconite mining operations on the Mesabi Iron Range are presented in Figure 33 and compiled grade/tonnage ore reserve calculations for these operations are given in Table 15. Table 15. Reported grade/tonnage of active taconite operations. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 126 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 33. Bedrock geology and iron mining features of the Mesabi Iron Range. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 127 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance D.1.3.2. Mn-(Fe) Resources of the Cuyuna Iron Range Since their discovery in 1904, it has been recognized that the iron-formations and associated ore deposits of the Cuyuna iron range in east-central Minnesota contained appreciable quantities of manganese which was extracted as ferromanganese ore from several mines on the North range from 1911 to 1984. The presence of this manganese resource sets the Cuyuna range apart from other iron- mining districts of the Lake Superior region. The Cuyuna iron range is about 160 km southwest of Duluth in Aitkin, Cass, Crow Wing, and Morrison Counties (Figure 34). It is part of an Early Proterozoic geologic terrane that occupies much of east- central Minnesota. The Cuyuna iron range is traditionally divided into the Emily, North range, and South range districts. The Emily district extends from the Mississippi River northward through Crow Wing County and into southern Cass County, and comprises about 1165 square kilometers. Although extensive exploratory drilling has been conducted in the Emily district, mining never commenced. The North range, a much smaller area about 19 km long and 8 km wide, is near the cities of Crosby and Ironton in Crow Wing County and was the principal site of mining activity (Figure 34), which largely ceased by 1970. The South range, where only a few underground mines were operated in the 1910s and 1920s, comprises an area of northeast-trending, generally parallel belts of iron-formation extending from near Randall in Morrison County northeast for about 100 km. In addition to the three named districts, numerous linear magnetic anomalies occur east of the range proper, and may indicate other poorly defined beds of iron-formation. Figure 34. Bedrock geology and open pit Fe-Mn mine map of the North Range of the Cuyuna Iron Range. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 128 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Three major insights regarding the geology of the Cuyuna range have emerged from the geologic mapping and associated studies of Southwick, et al., (1988) which utilized geophysical and drilling data. First, there is clear evidence that iron sedimentation occurred at several different times and under varying geological conditions, which invalidates the stratigraphic premises of Morey (1978). Major iron- formations are associated stratigraphically with volcanic rocks in the South range, with black shale and argillite in the North range, and with shallow-water deposits of sandstone and siltstone in the Emily district. Second, the iron-rich strata of the Emily district are correlative with the Biwabik Iron Formation of the Mesabi Range, as inferred by Marsden (1972) and Morey (1978). However, they and the other sedimentary rocks of the well-known Animikie Group occur above a major deformed unconformity that cuts across previously deformed, somewhat older sedimentary and volcanic rocks of the North range. There, a prominent iron-rich unit named the Trommald Formation and several other units beneath the unconformity form part of a locally twice-deformed sequence. Therefore, the rocks of the North range and the Emily district cannot be correlative, but are separate stratigraphic entities. Because the stratigraphic succession of folded sedimentary rocks on the North range comprises a distinct stratigraphic entity, Southwick, et al. (1988) referred to it informally as the North Range group with the understanding that a formal name may be justified at a later time. As defined by Schmidt (1963), the stratigraphic sequence in the North range consists of a quartz-rich lower unit named the Mahnomen Formation, a middle iron- and locally manganese-rich sequence assigned to the Trommald Formation, and an upper greywacke shale interval called the Rabbit Lake Formation. Third, Southwick, et al. (1988) recognized several geophysically defined structural discontinuities in the southern part of the Cuyuna iron range, within and southeast of the South range. These discontinuities are marked by demonstrable contrasts in metamorphic grade, by differing structural styles, and by different lithic components. One of the most pronounced of these, the Serpent Lake structural discontinuity, passes along the south edge of the North range. This discontinuity is interpreted as a tectonic boundary, probably involving major thrust faults between slices of folded rocks. Thus, it seems fairly certain that the iron-rich strata of the South range are not correlative with either the Trommald Formation of the North range or the iron-rich strata of the Emily district. The fact that iron-formation occurs within three different stratigraphic and structural contexts in the Cuyuna iron range is of considerable importance to the ultimate development of the manganese resource. Because we now recognize that the Emily district, the North range, and the South range are separate entities, we can no longer develop regional syntheses that extrapolate mineralogical and structural attributes from one entity to another. Several attempts have been made over the last 70 years to estimate the size of the manganese resources of the Cuyuna iron range. For example, Lewis (1951) estimated that 455 million metric tons of manganiferous iron-formation containing 2 to 10 percent manganese were available to open-pit mining to a depth of 45 meters. Dorr, et al., (1973) used that estimate to establish that the Cuyuna range contains approximately 46 percent of known manganese resources in the United States. US Steel geologist Richard Strong (1959) estimated iron and manganese resources from several well-drilled deposits in the Emily District, and Beltrame, et al. (1981) estimated a minimum of 170 million metric tons of manganiferous rock with an average grade of 10.46 weight percent manganese. All of these grade/tonnage estimates (Lewis, 1951; Strong, 1959; Beltrame, et al., 1981) should be considered with a certain amount of skepticism for at least two reasons. First, the manganese data were, for the most part, byproducts of data that were acquired originally by various mining companies as they explored for iron. Second, the various estimates were prepared for different reasons at different times, using NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 129 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance different data bases and methodologies. Therefore, the results are neither comparable, nor do they necessarily reflect the actual resource. Table 16 lists manganese resource grade and tonnages for properties studied by Strong (1959) and Beltrame, et al. (1981) and their locations are presented in Figure 35. Despite their problematic nature, the estimates of Lewis (1951) and Beltrame, et al. (1981) do show that the Cuyuna range contains a large, but low-grade resource. This large size, combined with the fact that the manganese deposits are located in an established mining district, makes the Cuyuna range an ideal place to study geological and technological factors needed to evaluate this and other sedimentary manganese deposits in the United States. Especially important are studies of the geologic habit of the manganese and the controls on its distribution and subsequent concentration into deposits of minable size. Table 16. Manganese grade and tonnage estimates from reports by Strong (1959) and Beltrame, et al. (1981). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 130 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 35. Bedrock geology and location map of properties outlined in reports by Strong (1959) and Beltrame, et al. (1981) that includes manganese grade-tonnage estimates. Labeled parcels correlate with the MAP ID column in Table 16 and are those with an estimated resource greater than 100,000,000 pounds of manganese metal. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 131 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance D.2. Aggregate and Byproduct Resources D.2.1.Byproducts Aggregate resources are mined throughout the state (Figure 36) and have been described in a variety of references (Austin, 1972; Davidson, 1972; Miller, et al., 2002; Jirsa and Boerboom, 2003; Oreskovich, et al., 2004; Zanko, et al., 2003; Boerboom, et al., 2005; Severson, et al., 2009; Zanko, et al., 2010). In addition, the Minnesota Department of Transportation provides an aggregate sources database with gravel pit and rock quarry aggregate information. Minnesota produces a wide variety of aggregates and byproducts (Table 17). Locally, the mining of carbonate rocks in southeastern Minnesota produces fine-grained carbonate products used as agricultural lime, and coarse fines which are used in other applications. Pond fines are commonly produced in and around the Twin Cities metropolitan area and are also produced locally out-state. Quarry stone (dimension stone) resources are mined throughout the state and vary from coarse-grained mafic plutonic rocks associated in the Duluth Complex (NE Minnesota), to felsic plutonic rocks and granitic gneisses in central Minnesota, to dolomitic quarry stone in south central and southeastern Minnesota. Miscellaneous resources occur locally throughout the state, and include baghouse dust, boulders, drilling dust, filter cake, foundry sand, over-sized rocks, process wastes, sandstone rubble, and tower sand. The lithogeochemistry of these materials is currently being compiled so that analysis for potential resources amenable to hydro-metallurgical processing can be evaluated. Table 17. Summary of aggregate and byproduct resources in Minnesota. Data compiled from Zanko, et al., (2003), Oreskovich, et al. (2004), and the Minnesota Department of Transportation Aggregate Source Information System (ASIS). MATERIAL TYPE NUMBER OF LOCATIONS MINNESOTA REGIONS Aggregate Resources 8151 Throughout MN Ag-Lime 48 Southeastern MN Coarse Fines 11 Southeastern MN, North-Central MN Pond Fines 22 Southern MN, Northeastern MN (Mesabi Range) Quarry Stone 14 Southern MN, Central MN, Northeastern MN Taconite Tailings 5 Northeastern MN (Mesabi Range) Other 9 Throughout MN Iron mining byproducts, such as course tailings, are produced along the Mesabi Iron Range (Figure 36) (Zanko, et al., 2003; Zanko, et al., 2010). Zanko, et al. 2003 conducted detailed lithogeochemical analyses of tailings from the EVTAC (United Taconite), Hibtac, Minntac, Minorca and Northshore processing facilities and reported rare earth element concentrations normalized to the bulk earth (Hickey et al., 1986) and North American shale (Gromet, 1984) standards (Figures 37 and 38). Relative to the “Bulk Earth Standard” (Hickey, et al., 1986), coarse taconite tailings appear to be moderately NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 132 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance enriched in cesium (40-~160 times), slightly enriched (>1 - ~20 times) in rubidium, thorium, niobium (with the exception of Hibtac and Northshore), lanthanum, cerium, strontium, neodymium, samarium yttrium and ytterbium, and depleted (<1 times) in zirconium (with the exception of Minntac and EVTAC (United Taconite). Relative to the North American Shale Composite composition (Gromet, et al. 1984), coarse tailings consistently have enrichment factors less than ~20x for all rare earth elements. These enrichment factors are significantly below enrichment factors normally present in rocks that are processed for rare earth elements. Figure 36. Distribution of aggregate and byproduct resources within Minnesota. Geographical locations derived from Oreskovich, et al. (2004) and the Minnesota Department of Transportation Aggregate Source Information System. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 133 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 37. Comparison of tailings compositions (Zanko, et al., 2003) relative to a bulk earth composition (Hickey, et al., 1986). Figure 38. Comparison of tailings compositions (Zanko, et al., 2003) relative to the North American Shale Standard (Gromet, et al., 1984). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 134 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Our current understanding of the materials that comprise aggregate and byproduct resources within the state suggests that most will not be high priority targets for hydrometallurgical processing for major or trace elements (including critical mineral resources). Compilation of lithogeochemical analyses from selected rock units utilized for dimension stone is currently being undertaken. Granitoid dimension stones from east-central Minnesota are believed to be similar in age to the Wolf River Batholith in Wisconsin, which has elevated rare earth element concentrations relative to other granitoid rock bodies in the upper Midwest. Evaluation of the lithogeochemistry of the Minnesota granitoid rocks may provide additional information regarding whether waste products from dimension stone mining may be amendable for hydrometallurgical processing to produce trace metals and/or rare earth elements. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 135 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix E: Waste Resources of Minnesota Appendix E presents some of the waste resources that may contain critical metals. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 136 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance E.1. Waste Resources in Minnesota E.1.1. Waste-to-Energy Facilities in Minnesota Waste-to-energy (WTE) facilities burn mixed municipal solid waste (MMSW) and refuse-derived fuel (RDF) in combustors to generate steam that is used to produce electricity. In Minnesota, there are eight WTE facilities: Great River Energy-Elk River Station in Elk River, Hennepin Energy Resource Co. (HERC) in Minneapolis, Olmsted Waste-To-Energy Facility in Rochester, Perham Resource Recovery Facility in Perham, Polk County Solid Waste Resource Recovery Plant in Fosston, Pope/Douglas Solid Waste Management in Alexandria, Xcel Energy – Red Wing Steam Plant in Red Wing, and Xcel Energy – Wilmarth Plant in Mankato (Michaels & Krishnan, 2018). Although Minnesota’s solid waste hierarchy prioritizes waste-to-energy over landfilling, critics of this technology are concerned about possible air pollution and disposal of ash resulting from the combustion of mixed municipal solid waste and refuse-derived fuel. E.1.2. Coal Combustion Residuals Coal combustion residuals (CCR) are generated from the combustion of coal while generating steam to produce electricity by electric utilities and independent power producers. CCR includes fly ash, bottom ash, boiler slag, and flue gas desulfurization materials. CCR can be sent off-site for disposal or beneficial use or disposed in on-site landfills or surface impoundments. A potential list of CCR generating facilities in Minnesota are shown in Table 18 below. Table 18. Summary of coal combustion residual generating facilities in Minnesota. Plant Operator County Black Dog Power Station Xcel Energy Dakota Clay Boswell Power Station Minnesota Power Inc. Itasca Fox Lake Generating Station Alliant Energy Martin NSP-M Minnesota Valley Plant Xcel Energy Granite Falls Riverside Power Station (NSP) Xcel Energy Hennepin Sherburne County Power Station Xcel Energy Sherburne Syl Laskin Minnesota Power Inc. St. Louis Allen S. King Xcel Energy Washington High Bridge Xcel Energy Ramsey Taconite Harbor Energy Center Minnesota Power Inc. Cook Silver Bay Power Co. Cleveland Cliffs Inc. Lake Hoot Lake Otter Tail Power Co. Otter Tail Austin Northeast City of Austin Mower Hibbing Hibbing Public Utilities Commission St. Louis Silver Lake Rochester Public Utilities Olmsted Virginia City of Virginia St. Louis Willmar Willmar Municipal Utilities Kandiyohi NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 137 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance E.1.3. Waste Electrical and Electronic Equipment (WEEE) According to the Minnesota Pollution Control Agency, electronic waste, or e-waste, includes any tool, equipment, or appliance containing a printed circuit board or a cathode ray tube (CRT). E-waste includes computers and peripherals, such as keyboards, monitors, and mice. It also includes many common business items like telephones, cameras, scanners, manufacturing control equipment, and medical devices (Minnesota Pollution Control Agency, 2011). In Minnesota, approximately 199.4 million pounds of household electronic waste was collected for recycling between 2013 and 2018 (Minnesota Pollution Control Agency, 2018). Minnesota's electronics recycling legislation was signed into law in May 2007 (Minnesota Electronics Recycling Act (115A.1310). In Minnesota, the Minnesota Pollution Control Agency (MPCA) regulates E- wastes under the Hazardous Waste Rules. E-waste is classified as hazardous because of its potential to release toxic heavy metals, such as lead, cadmium, and mercury, into the environment if not managed and disposed of properly. The law formally identifies many stakeholders and details specific responsibilities and requirements for each, including registration and annual reporting on their activities. Stakeholders affected by the Minnesota Electronics Recycling Act must be registered with the MPCA. By law, organizations that are not registered cannot collect or recycle covered electronic devices (CED). Stakeholders involved in e-waste recycling are shown below: Manufacturers A manufacturer makes video display devices for sale under its own brand, or has others make products under its brand. Collectors A collector is “a public or private entity that receives covered electronic devices from households and arranges for the delivery of the devices to a recycler.” Recyclers Recyclers accept “covered electronic devices” from households or collectors of these devices in Minnesota. Recyclers dismantle the devices for further processing or process the devices into raw materials for use in new products. A map of Minnesota manufacturers, collectors, and recyclers can be found in Figure 39. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 138 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 39. Map of waste-to-energy, e-waste recycling, and coal-fired power plants in Minnesota. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 139 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix F: Short Case Study on Vale’s Long Harbour Hydrometallurgical Processing Plant Appendix F illustrates the application development of hydrometallurgical technologies at Vale’s Long Harbor facility. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 140 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance F.1. Introduction A relatively recent example of a hydrometallurgical facility operating in an environment similar to Minnesota’s is Vale Inco’s Voisey’s Bay and Long Harbour Processing Plant (LHPP) which are located in Labrador and Newfoundland, Canada, respectively. This is of interest for the current “LCCMR Develop Emerging Hydrometallurgy Technologies” project for many reasons. First, the material that is fed to the LHPP is a nickel sulfide concentrate produced from Voisey’s Bay Mine located in Labrador. Nickel sulfide is most commonly used as feed to smelters instead of a hydrometallurgical processing plant, but in this case, Vale developed a novel hydrometallurgical process to produce high-purity nickel, cobalt, and copper products. There were economic, political/legal, and technological forces at play that ultimately led Vale to develop a hydrometallurgical process rather than a traditional smelting process for this project. This case study is a brief review of this project and serves as a source of information for review and to extract lessons learned. F.2. Nickel Sulfide Ores Approximately half of the world’s primary nickel production is from nickel sulfide ores like pentlandite, which has the chemical formula (Ni, Fe)9S8, and contains approximately 36% Ni, 30% Fe, and 33% S by weight. Other sulfide minerals often associated with pentlandite are pyrrhotite (Fe8S9) and chalcopyrite (CuFeS2), with additional accessory ore minerals containing varying degrees of copper, cobalt, silver, gold, and platinum-group elements (Crundwell, et al., 2011). F.2.1. Typical Processing of a Nickel Sulfide Ore An example process flowsheet for processing of nickel sulfide ore can be seen in Figure 40. As illustrated, nickel sulfide ore is commonly crushed and ground to a size that achieves liberation (in this example, less than 50 microns), followed by a bulk sulfide flotation process. The bulk sulfide contains both nickel and copper sulfides, and therefore often undergoes a differential flotation process in which the copper is separated into a separate stream and sent to a copper smelter. The remaining nickel concentrate stream is then sent to either a flash smelting or electric furnace melting step to produce a molten sulfide matte product, which is subjected to a Peirce-Smith converting process to reduce the iron content. The product, a molten low-iron sulfide matte, is then used as a feedstock to produce the nickel and other byproducts via hydrometallurgical and/or pyrometallurgical techniques (Crundwell, et al., 2011). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 141 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Figure 40. Main process steps for extracting nickel and cobalt from sulfide ores (Source: Crundwell, et al., 2011). F.2.2. Smelting vs. Hydrometallurgical Processing of Nickel Concentrate It is possible to use concentrate as the raw feed for a hydrometallurgical process; however, historically this has been found to be more difficult for recovery of both the precious metals and base metals. Therefore, it is more common to use smelting first, due to its ability to remove gangue, sulfur, and iron from the concentrate, followed by further processing using pyrometallurgical and/or hydrometallurgical process (Crundwell, et al., 2011). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 142 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance F.3. Voisey’s Bay Mill F.3.1. Deposit The Voisey’s Bay nickel deposit was discovered in 1993 by Archean Inc., and through continued exploration, it has been estimated to contain 141 million tons at 1.6% nickel (Anon., 2020b). According to Wells, et al. (2007): “The deposit is a 600 m long by 350 meter wide by 110 meter deep zone of massive sulfides with a feeder zone of troctolite-gabbro below, which contains disseminated sulfides. The deposit was covered by about 20 meters of quaternary overburden which was scraped off to reveal the ore. The total reserve in the Ovoid was 32 million tonnes at an average grade of 2.99%, Ni, 1.73% Cu and 0.15% Co. The massive sulfide ore consists mainly of a hexagonal pyrrhotite with blocky pentlandite, chalcopyrite, cubanite and magnetite…the only liberation concern is in the chalcopyrite which has fine pentlandite disseminated in many particles…this intergrowth makes production of copper concentrate with low nickel assay challenging and requires fine grinding of the copper rougher concentrate.” F.3.2. Process In 1995-1998 and 2001, Vale Inco, a subsidiary of Vale, conducted various bench- and pilot-scale comminution and beneficiation test programs with disseminated sulfide ores. In 2001, market conditions dictated that a higher-grade nickel sulfide concentrate be produced than originally planned to reduce the cost of concentrate transportation and smelting (Wells, et al., 2007). This material would also ultimately be the feed for a new processing plant within the Labrador province according to agreements between Vale and the Labrador and Newfoundland governments, as described in the following sections. Through various iterations of bench-scale studies and three pilot-scale testing programs, a flowsheet was developed to produce a >20% Ni concentrate from a feed blend of 75% massive sulfide and 25% disseminated sulfide (Wells, et al., 2007). Mineral processing included various stages of milling and sulfide flotation to produce three products: a nickel sulfide concentrate, a copper sulfide concentrate, and a middlings concentrate that was ultimately added to the nickel sulfide concentrate stream. The chemical reagent suite included lime for pH adjustment, Dowfroth 250 as a frother, and Flex 31 (a blend of SIPX and auxiliary surfactant) as a collector (Wells, et al., 2007). The final flowsheet that was used at the Voisey’s Bay mill can be seen in Figure 41. Figure 41. Voisey's Bay mill flow sheet design circa 2005 (Wells, et al., 2007). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 143 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Open pit mining started in 2005 and currently hosts approximately 500 people who support the mining and milling operations. It was announced in 2018 that Vale would be extending the life of the mine by at least 15 years by constructing an underground mine (Anon., 2020b). Transportation of the nickel sulfide concentrate is currently conducted via large bulk carrier ships from Voisey’s Bay to their final destinations, including smelters or the Long Harbour Processing Plant (LHPP). The first nickel concentrate was shipped from Voisey’s Bay to the LHPP in May 2015 (Campbell, 2015). F.3.3. Decision for Hydrometallurgical Processing Through various negotiations between Vale and the government of Newfoundland and Labrador, it was agreed that the nickel sulfide concentrate would be shipped to Sudbury, Ontario, and Thompson, Manitoba, smelting facilities until 2011; afterwards, Vale had to construct a new processing facility in southeastern Newfoundland to create jobs within the province (Anon., 2020a,b). This agreement also limited the amount of nickel concentrate that could be exported outside the Province, as well as replace all nickel concentrate they export (Vale, 2012). Using hydrometallurgical processing would allow for discrete nickel, copper, and cobalt products to be produced at the hydrometallurgical plant. This hydrometallurgical process was also thought to be “more efficient and sustainable way to process concentrate than the more traditional methods of smelting and refining” (Roberts, 2014). Other advantages of hydrometallurgy include no SO2 emission, improved nickel and cobalt recovery, and reducing the energy requirements for producing the final nickel product (Chapman & Zacharewych, 2018; Vale, 2012). F.4. Long Harbour Processing Plant F.4.1. Process The Long Harbour Processing Plant (LHPP) uses ground nickel concentrate to produce final nickel, cobalt, and copper products. The process involves a chlorine pre-leach, a pressure-leaching autoclave, a solid- liquid separation, a series of solvent extraction for recovering each element independently, and electrowinning to produce the final products (Crundwell, et al., 2011). According to Chapman & Zacharewych (2018): “The purpose of the Impurity Solvent extraction circuit is to remove impurities such as Cu, Mn, Ca, Pb, Fe and Zn from the pregnant leach solution prior to cobalt solvent extraction. The purpose of this cobalt solvent extraction circuit is to separate cobalt from nickel contained in the pregnant leach solution. In the copper solvent extraction circuit, copper is stripped by spent electrolyte and sent to Copper Electrowinning. The nickel electrowinning circuit produces both finished nickel rounds and concentrate leaching lixiviant. Nickel metal is produced by electrowinning where the nickel deposited at the cathode, and oxygen, chlorine, and acid are all generated at the anode. The anode products are used for concentrate leaching in both the pre-leach and pressure oxidative leach circuits. The feedstock to the Ni electrowinning circuit is purified rich nickel solution from Cobalt Solvent Extraction. The cobalt electrowinning circuit produces finished cobalt. Cobalt metal is produced by electrowinning, with the cobalt deposited on mandrels as rounds while oxygen and acid are generated at the Pb anodes. The feedstock to the Co electrowinning circuit is strong cobalt solution from the Co solution purification circuits. Cobalt anolyte is returned to the Co SX circuit as strip solution. The purpose of the copper electrowinning circuit is to recover copper as an electrowon cathode product from a purified copper solution generated in copper solvent extraction and return an acidic spent copper electrolyte back to copper solvent extraction for use as the strip solution. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 144 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance The waste from the nickel electrowinning process is recycled back to the pre-leaching and autoclave steps in the process, and the organics used in solvent extraction are also recycled. The major discharge streams are the neutralized solid residue and the impurity bleed stream in the purification circuit.” F.4.2. Plant Construction and Commissioning This process was piloted at a demonstration plant in country of Argentina and provinces of Newfoundland, and Labrador, between 2004-2008 (Anon., 2020a). The total cost of the research was estimated at over $200M CAD over six years, from approximately 2002-2008 (Campbell, 2015; Vale, 2020). Due to the use of chlorine gas in the process, anti-corrosive materials were needed throughout the operation, which likely resulted in high capital costs. This also means there are significant environmental, health, and safety concerns with this process (Cheng & Urbani, 2005). Long Harbour Processing Plant (LHPP) construction was completed in 2009 at a cost of $2-2.5B (Anon., 2020b; Roberts, 2014). The plant was designed to produce 50 thousand tons per annum nickel, with associated cobalt and copper products. After many delays and cost over-runs, the LHPP was constructed and production began in July 2014, with final costs estimated at greater than $4.25B (Campbell, 2015; Roberts, 2014). Commissioning and early production was completed with nickel matte material from Indonesia, with the first small load of concentrate from Voisey’s Bay in May of 2015 (Campbell, 2015). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 145 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix G: Biohydrometallurgical Technologies Appendix G reviews the application of biohydrometallurgical process in the areas of metal extraction and minewater remediation. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 146 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance G.1. Review of Biohydrometallurgy Biohydrometallurgical technologies that are applied to recover metals from polymetallic ores, waste tailings, and remediation of toxic wastes are briefly reviewed, as well as advancements in water and solid mine waste bioreclamation, metals biosorption, and wetland treatment of acid mine drainage. The review specifically focuses on biohydrometallurgical technologies that have been demonstrated at pilot scale or implemented at commercial scale. Biological processes (also referred as bioleaching, biohydrometallurgy, or biomining) encompasses the overlapping areas of microbiology, biochemistry, genetic engineering, and extractive metallurgy. These processes, which employ deliberate use of microorganisms to recover metals, have been commercially utilized since 1950s (Brierley, 2014). Today biological processes are commercially practiced for extraction of nickel, zinc, cobalt, silver, and uranium (Brierley, 2016), and biohydrometallurgical processes account for around 20% of the world’s mined copper and 3% of mined gold production (Brierley, 2016). Additionally, biological processes are utilized for removal of heavy metals from industrial, mining, and agricultural waste runoffs. G.2. Commercial Applications of Biohydrometallurgy in Mining Sulfidic Ores G.2.1. Bioleaching-Heap Reactors According to Brierley (2014), 23 copper heap bioleaching plants have been constructed since 1980, and 16 are currently in operation. The first known industrial patent for a biohydrometallurgical process was issued in 1954 to Kennecott Copper Corporation, which used a bio-heap-leach process at a copper dump leach operation. The patent claimed the use of thermophilic microbes for oxidation of ferrous sulfate to ferric sulfate, which acts as a lixiviant for the oxidation of sulfide minerals. The patent also recognized the need for aeration to promote the bio-oxidation of the ferrous sulfate. Advancements in heap stacking, forced aeration systems, and a variety of inoculation technologies have expanded the use of bioleaching processes at relatively large scales (Free, 2014). The Talvivaara mine located in subarctic eastern Finland utilizes bioleaching for recovery of nickel, zinc, cobalt, and copper from low-grade polymetallic sulfide minerals (black schist deposit). The leaching is done in heaps with an acidic solution containing a complex consortium of microorganisms of mesophilic and thermophilic archaea. The internal temperatures in the heap range from 10-90° C with heat generated by rapid oxidation of pyrrhotite in the ore, which supports the growth of the extreme thermophiles. After subsequent oxidation of pyrite, pentlandite, and sphalerite, the ore is subjected to secondary bioleaching to recover cobalt, which is locked in the chalcopyrite matrix. Copper, nickel, cobalt, and zinc are recovered from pregnant liquor solution using hydrogen sulfide and pH control (Brierley, 2016). Table 19 lists selected examples of bio-heap leaching plants processing copper ores (Brierley, 2014). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 147 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 19. List of bio-heap leaching plants (Source: Brierley J., 2014). Plant Name Country Operator Annual Cathode Copper Production, tons Morenci USA Freeport McMoran 380,000 Nifty Copper Australia Metals X 16,000 Cerro Colorado Chile BHP 115,000 Ivan-Zar Chile Compania Minera Milpro 12,000 Punta Del Cobre Chile Sociedad Punta del Cobre 8,000 Quebrada Blanca Chile Teck Resources 75,000 Andacollo Cobre Chile Teck Resources 21,000 Cerro Verde Peru Freeport McMoran 54,200 Zaldivar Chile Barrick Gold 150,000 Los Bronces Chile AngloAmerican 50,000 Lomas Bayas Chile Glencore 60,000 Escondida Chile BHP 180,000 G.2.2. Bioleaching-Stirred Tank Reactors The continuous stirred-tank reactor for biological processing of sulfide concentrates was pioneered by Gencor Process Research (now BHP Process Research) South Africa for the recovery of gold from sulfidic-refractory gold ores. The first commercial bioxidation plant was built by Goldfields in 1986 at the Fairview Mine in South Africa. The process has been commercially used for more than 30 years, and is currently used in several locations throughout the world (see Table 20). The largest bioxidation operation is located in Uzbekistan, which processes around 2000 tons per day of sulfidic refractory gold flotation concentrate (Free, 2014). Since its inception in 1986, bioxidation technology has also been expanded for bioleaching cobalt from pyritic tailings. The bioxidation process operates at a temperature range of 40 to 45°C and at a pH range of 1.2 to 1.6 at dissolved oxygen level of more than 2 ppm. The reactors are aerated to provide both oxygen and carbon dioxide to assist the bacterial oxidation. The total residence time varies from 4 to 6 days. In some instances, additional nutrients are added to optimize the process. The process uses a range of bacteria: Thiobacillus ferroxidans, Thiobacillus thiooxidans, and Leptospirillum ferroxidans (Free, 2014). A list of current operating mines using bioxidation plants with continuous stirred reactors is shown in Table 20 (Brierley, 2014). NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 148 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 20. List of continuous stirred tank bioreactor plants (Source: Brierley J., 2014) Mine Country Concentrate treated per day, tons Fairview South Africa 62 Wiluna Australia 158 Ashanti Ghana 960 Fosterville Australia 211 Suzdai Kazakhstan 520 Bogoso Ghana 820 Kokpatas Uzbekistan 2,138 Olimpiada Russia 8,220 G.3. Application of Bioleaching to Non-sulfide Ores (Manganese ores) In the 1990s, the U.S. Bureau of Mines investigated bioheapleaching as a means of recovering manganese from low-grade manganese ores from the Three Kids Mine in Arizona (Noble, et al., 1993). Leaching experiments were carried out in columns using indigenous heterophilic microorganisms and sugarcane molasses as the nutrient source. Manganese extractions of more than 90% were achieved in 12 weeks of bioleaching column tests. The Bureau also investigated two methods to recover manganese from the bioleach pregnant leach solution: 1) adsorption onto weak cation exchange resin, followed by stripping and precipitation techniques; and 2) direct precipitation of the manganese as MnCO3 using ammonium carbonate. Both methods removed 95% of solubilized manganese as carbonate salt. The study concluded that these low-cost technologies enhanced the potential for future commercialization of a biological process for extracting manganese from low-grade domestic ores (Noble et. al., 1993). G.4. Applications in Bioremediation in the Minerals Industry Biological treatment of mine wastewaters is attractive because microorganisms are: ● Capable of reducing dissolved species in solution to form compounds which are amenable to conventional solid-liquid separation, ● Capable of oxidizing species into compounds that are readily adsorbed or complexed for removal purposes, ● Capable of providing adsorption sites that facilitate removal of toxic species, and ● Capable of altering the toxicity of certain species (Free, 2014). Examples of commercial applications of biotechnology to mine site wastewater treatment and reclamation are presented below. G.4.1. Sulfate Removal The most widely used applications of microorganisms in mine water treatment use sulfate reducing bacteria to reduce sulfate to sulfide and elemental sulfur. The resulting hydrogen sulfide can react with metal cations to produce metal sulfide precipitates that can be removed using conventional solid-liquid separation technologies. G.4.2. Biosorption of Metals from Wastewater Biosorption is the property of microbial biomass to bind metals to charged functional groups such as amino, imino, carboxylic, sulfonic, phosphonic, carbonyl, ether, alcohol, oxime, phenolic, thiether, NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 149 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance thiophenolic, and substituted phosphine. In most instances, the biomass is immobilized on organic polymers (such as polyethyleneimine, glutaraldehyde, carrageenan, and alginate) or inorganic polymers such as silica gel or polysulfone beads (Free, 2014). Typical requirements for biomass are good mechanical integrity, high particle porosity or surface area, hydrophilicity, low interference from other species, ease of handling and regenerability (Conard, 1992). Biosorption is used to sequester heavy metals from industrial effluents and for recovering critical metals from processing solutions (Marshall & Ikhu-Omoregbe, 2012). Adsorption capabilities of various biomass types is shown in Table 21 below (Free, 2014). Table 20. Biosorption capabilities of killed biomass (after Free, 2014). Biomass Type Metal Uptake (mg/g) Freshwater alga Silver 86-94 Brown seaweed Cadmium 215 Brown seaweed Cobalt 100 Bacillus biomass Chromium 118 Bacillus subtilis Copper 152 Rhizopus arrhizus Mercury 54 Fucus vesiculosus Nickel 40 Bacillus subtilis Lead 601 Freshwater alga Palladium 436 Streptomyces longwoodensis Uranium 440 G.5. Application of Biohydrometallurgy to Minnesota’s Mineral Resources Biohydrometallurgy is widely applied to commercially extract metals like copper, nickel, gold, cobalt, and others from low-grade ores. The attractiveness of using biohydrometallurgical techniques is that they are technologically simple, involve relatively minor capital and operating expenses, and are capable of producing environmentally acceptable effluent that are suitable for disposal on conventional tailings dams (Du Plessis et. al, 2007; Peterson & Dixon, 2007; Domic, 2007). Potential research and development opportunities for bio-hydrometallurgy include: • Identification of novel strains of bioleaching microorganisms that are specific to minerals: pyrrhotite, cubanite, bornite, chalcopyrite, pentlandite, manganite, pyrolusite, ilmenite, and titanomagnetite. • Scaling up technologies for the production of genetically modified bioleaching microorganisms. • Carrying out bioleaching amenability tests and pilot scale validation tests using different low- grade sulfide and oxide ores present in Minnesota. G.5.1 Development of Engineered Biosorbent from Minnesota Biomass The traditional techniques for the recovery of metals from processing solutions or waste effluents include precipitation, solvent extraction, adsorption, ion exchange, and membrane processes. Such processes have several economical and technical constraints. The precipitation processes have limited applications where stringent regulatory limits have to be achieved. Ion-exchange and membrane processes are relatively effective; however, they require expensive ion-exchange resins (adsorbent NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 150 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance materials), and membrane processes generate waste brines that requires complex residual management practices (Free, 2014). There is a need to develop a cost-effective alternative for removal of metals from solutions as well as for removal of metals from industrial mining (e.g., selanate, selenite, arsenate, arsenite etc.), and agricultural activities. Biomass is abundantly available in Minnesota, however, current knowledge on the application of Minnesota’s biomass resources for biosorption is limited. NRRI should explore opportunities to utilize Minnesota’s forest resources in order to design suitable biosorbents for specific metal binding abilities. Research efforts should focus on understanding the mechanism of metal adsorption by microorganisms as a means to engineer a biosorbent with increased metal adsorption capacity and improved kinetics for metal recovery. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 151 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix H: Application of Hydrometallurgy to Mine Wastewater Treatment Appendix H reviews the application development of hydrometallurgical processes in mine wastewater treatment. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 152 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Application of Hydrometallurgy to Mine Wastewater Treatment Any mining activity that exposes mined materials to air and water has the potential to generate leachate with increased solute concentrations, which can significantly impact water quality during operations and after closure and influence the industry’s social license to operate. This report points out some areas where the field of hydrometallurgy will be able to contribute to protecting the water quality and meet stricter discharge regulations that have lower permissible contaminant levels. H.1. Importance As mining operations evolve from high-grade to low-grade resources, the volumes of mined surface material and water consumption increases exponentially, along with a wide range of contaminants that appear in wastewater. The strict regulatory limits on mine discharge contaminants present a challenge to the industry to investigate and develop cost-effective technologies to reclaim, reuse, and recycle mine wastewater. The goal of water treatment technologies include: ● To re-use water in processing plants ● To protect equipment from corrosion or fouling by scaling ● To recover valuable and hazardous metals ● To achieve contaminants levels required by statutory organizations H.2. Existing Mine Wastewater Treatment Technologies Over the past few decades, a wide variety of treatment technologies for the removal of residual constituents in mine effluents have been studied, developed, and applied. Key considerations for selecting the most suitable water treatment method are water chemistry, flow rate, treatment targets, and solid-liquid residue management. Proven treatment technologies classified by the type of unit operation or process, or by the principal constituent removal function performed are listed in Table 22. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 153 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 21. List of commercially practiced wastewater treatment technologies at mine sites. Technology Category Typical Applications Purpose Examples Neutralization Acid mine drainage Removal of excess acidity or alkalinity Acid Neutralizing Chemicals- Calcium hydroxide (lime), sodium carbonate (soda ash), sodium hydroxide (caustic soda); Alkali Neutralizing Chemicals- Carbonic acid, sulfuric acid, hydrochloric acid Chemical Precipitation Saleable metals precipitation, heavy metals removal from effluent Removal of metallic and non- metallic components Precipitation of metal sulfides Precipitation of metal hydroxides Precipitation of metal carbonates. Precipitation of sulfates/phosphorus Adsorption Removal of arsenic, cadmium and selenium Removal of heavy metals. Adsorption of selenite or cadmium hydroxides Arsenic sequestration Phosphorus adsorption on iron hydroxides Ion Exchange Removal of potentially toxic inorganic compounds or ions Deionization of water; removal of metals contaminants from waste waters Removal of nitrogen and phosphorus Removal of heavy metals Removal of total dissolved solids Cyanide recovery Membrane Processes (Reverse Osmosis, Ultrafiltration, Microfiltration, Nano- filtration, Electrodialysis) Removal of both major iron salts and metals/metalloids to low levels; Recover and reuse process water Desalination TSS & turbidity removal Hardness removal/wastewater softening Sulfate/nitrate removal Heavy metals removal Biological treatment Acid mine drainage, bioremediation, bio sorption Removal of sulfate and heavy metals Nitrogen removal Selenite and Selenate removal Sulfate removal Arsenic sequestration NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 154 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance H.3. Case Study 1: Water Treatment Plant at Eagle Mine LLC, Michigan Case study 1 illustrates the water treatment plant at the Eagle Mine in Michigan that is treating mine wastewater to meet the regulatory limitations. The discharge water quality is set by permit No. MI0058649 issued by the Michigan Department of Environmental Quality (MDEQ) authorization to discharge under NPDES. The wastewater treatment stages consist of: metals precipitation/sedimentation, filtration, reverse osmosis, microfiltration, ion exchange, and evaporation/crystallization (State of Michigan Department of Environmental Quality, 2015). The ion exchange regenerant and RO concentrate liquid wastes are sent to the evaporator and crystallizer system and converted to solids that are disposed of off-site as non-hazardous solid waste. The water treatment process generates a filter press waste stream consisting of dewatered solids from the clarification treatment process that is primarily comprised of calcium and magnesium, and a crystallizer waste stream, which is essentially sodium chloride (Eagle Mine, LLC, 2017). H.4. Case Study 2: Proposed Wastewater Treatment Plant at the NorthMet Project Polymet Mining, Inc. (Polymet) is proposing to develop the NorthMet copper nickel-platinum group elements (PGE) mine and associated processing facilities in northeastern Minnesota. A pilot study conducted by Polymet evaluated the following water treatment technologies: ● Greensand filtration for iron, manganese, and total suspended solids removal, ● Reverse osmosis for sulfate and dissolved solids removal, ● VSEP for RO concentrate volume reduction, ● Chemical addition for permeate stabilization, and ● Chemical precipitation of the reject concentrate for removal of metals and sulfate Table 23 presents the target wastewater treatment facility (WWTF) effluent concentrations for the different mine phases. Pilot testing of a WWTF with RO demonstrated that all of the target closure effluent concentrations could be achieved with the planned WWTF design (Minnesota Department of Natural Resources, United States Army Corps of Engineers, United States Forest Service, 2015). Pilot testing suggested construction of a Plant Site WWTP that uses reverse osmosis or similar membrane separation technology to treat any water that cannot be recycled prior to environmental discharge. This unit would be designed to achieve an effluent sulfate concentration that meets the 10 mg/L sulfate standard for waters used for the production of wild rice. A second Mine Site WWTF would use chemical precipitation and filtration to treat affected mine water as well as the reject concentrate from the Plant Site WWTP. After the reclamation stage the Mine Site WWTF would be converted to RO (or an equivalent treatment technology) to provide water treatment during post-closure maintenance. For RO operation, a distillation process would reduce the concentrate to a moist solid that would be disposed of offsite (Minnesota Department of Natural Resources, United States Army Corps of Engineers, United States Forest Service, 2015). Applicable surface water quality evaluation criteria are listed by use classification in Table 24. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 155 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 22. Wastewater treatment facility preliminary water quality targets (Source: Minnesota Department of Natural Resources, United States Army Corps of Engineers, United States Forest Service, 2015). Targets Operations Reclamation Closure and Post- Closure Maintenance Basis Metals (μg/L) Aluminum 125 125 125 M.R., part 7050.0222 Class 2B (chronic standard) Antimony 31 31 31 M.R., part 7050.0222 Class 2B (chronic standard) Arsenic 10 10 4 Federal Standard (pMCLs) Barium 2,000 2,000 2,000 Minn. Groundwater (HRL, HBV5, or RAA) Beryllium 4 4 4 Federal Standard (pMCLs) Boron 500 500 500 M.R., part 7050.0224 Class 4A (chronic standard) Cadmium 5.1 4.2 2.5 M.R., part 7052.0100 Class 2B (chronic standard) Chromium III 86 86 86 M.R., part 7052.0100 Class 2B (chronic standard) Cobalt 5 5 5 M.R., part 7050.0222 Class 2B (chronic standard) Copper 20 17 9.3 M.R., part 7052.0100 Class 2B (chronic standard) Iron 300 300 300 Federal Standard (sMCLs) Lead 10.2 7.7 3.2 M.R., part 7050.0222 Class 2B (chronic standard) Manganese 50 50 50 Federal Standard (sMCLs) Nickel 113 94 52 M.R., part 7052.0100 Class 2B (chronic standard) Selenium 5 5 5 M.R., part 7052.0100 Class 2B (chronic standard) Silver 1 1 1 M.R., part 7050.0222 Class 2B (chronic standard) NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 156 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Targets Operations Reclamation Closure and Post- Closure Maintenance Basis Metals (μg/L) Thallium 0.56 0.56 0.56 M.R., part 7050.0222 Class 2B (chronic standard) Zinc 260 216 120 M.R., part 7050.0222 Class 2B (chronic standard) General Parameters (mg/L) Chloride 230 230 230 M.R., part 7050.0222 Class 2B (chronic standard) Fluoride 2 2 2 Federal Standard (sMCLs) Hardness 250 200 100 Hardness PWQT chosen to establish PWQTs for metals with a hardness based standard Sodium 60% of cations 60% of cations 60% of cations M.R., part 7050.0224 Class 4A (chronic standard) Sulfate 250 150 9 Operations: Federal Standard (sMCLs) Long-term closure: M.R., part 7050.0224 Class 4A NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 157 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Table 23. Surface water quality evaluation criteria applicable to different classes of surface water (Source: Minnesota Department of Natural Resources, United States Army Corps of Engineers, United States Forest Service, 2015). Parameter Units Class 1B pMCL Class 1B sMCL Class 2A Class 2Bd Class 2B Class 3B Class 3C Class 4A Class 4B Class 5 Class 6 General Alkalinity mg/L -- -- -- -- -- -- -- -- -- -- -- Calcium mg/L -- -- -- -- -- -- -- -- -- -- -- Chloride mg/L -- 250 230 230 230 100 250 -- -- -- -- Fluoride mg/L 4 2 -- -- -- -- -- -- -- -- -- Hardness mg/L -- -- -- -- -- 250 500 -- -- -- -- Magnesium mg/L -- -- -- -- -- -- -- -- -- -- -- pH s.u. -- 6.5–8.5 6.5–8.5 6.5–9.0 6.5–9.0 6.0–9.0 6.0–9.0 6.0–8.5 6.0–9.0 6.0–9.0 -- Potassium mg/L -- -- -- -- -- -- -- -- -- -- -- Sodium mg/L -- -- -- -- -- -- -- -- -- -- -- Sulfate mg/L -- 250 -- -- -- -- -- 10 -- -- -- TDS mg/L -- 500 -- -- -- -- -- 700 -- -- -- Metals Total -- -- -- -- -- -- -- -- -- -- -- Aluminum µg/L -- 50–200 87 125 125 -- -- -- -- -- -- Antimony µg/L 6 -- 5.5 5.5 31 -- -- -- -- -- -- Arsenic µg/L 10 -- 2 2 53 -- -- -- -- -- -- Barium µg/L 2,000 -- -- -- -- -- -- -- -- -- -- Beryllium µg/L 4.0 -- -- -- -- -- -- -- -- -- -- Boron µg/L -- -- -- -- -- -- -- 500 -- -- -- Cadmium μg/L 5 -- 2.5 2.5 2.5 -- -- -- -- -- -- Chromium (III) μg/L 100 -- 86 86 86 -- -- -- -- -- -- Cobalt µg/L -- -- 2.8 2.8 5.0 -- -- -- -- -- -- Copper µg/L -- 1,000 9.3 9.3 9.3 -- -- -- -- -- -- Iron µg/L -- 300 -- -- -- -- -- -- -- -- -- Lead µg/L -- -- 3.2 3.2 3.2 -- -- -- -- -- -- Manganese µg/L -- 50 -- -- -- -- -- -- -- -- -- Mercury ng/L 2,000 -- 1.3 1.3 1.3 -- -- -- -- -- -- Nickel µg/L -- -- 52 52 52 -- -- -- -- -- -- Selenium µg/L 50 -- -- -- -- -- -- -- -- -- -- Silver µg/L -- 100 0.12 1.0 1.0 -- -- -- -- -- -- Thallium µg/L 2 -- 0.28 0.28 0.56 -- -- -- -- -- -- Vanadium µg/L -- -- -- -- -- -- -- -- -- -- -- Zinc µg/L -- 5,000 120 120 120 -- -- -- -- -- -- NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 158 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix I: List of High Value Products Appendix I provides a tentative list of key products in each of the value chains that could be potentially produced from regional resources. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 159 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Regional Resource/Value Chain Raw Material Feedstock Bulk Commodities Engineered Product Chemical compound Titanium -Oxide Bearing Ultramafic Intrusions Ilmenite concentrate/pellet TiO2 slag, Titanium sponge metal TiO2 pigment, Mn- Li-Ti battery material (Li-Ti oxide anode), titanium alloys Titanium iodide, barium titanate, strontium titanate, titanium tetrachloride, alkyl/butyl titanate, titanium oxide chloride, potassium titanate, titanium disulfide, titanium hydride, titanium carbide, titanium nitride Vanadium- Titanomagnetite - Oxide Bearing Ultramafic Intrusions Titano-magnetite concentrate Vanadium slag/vanadium metal/ferrovanadium Vanadium pentoxide, vanadium flow battery chemicals vanadium trioxide, vanadates, vanadyl sulfate, vanadium halides, vanadium carbides, organic vanadium compounds, vanadium nitrides, vanadium hydrides, vanadium silicides, Manganese ores - Cuyuna Iron Range Manganese slag/concentrate Ferromanganese, silicomanganese Electrolytic manganese metal (EMM), Electrolytic manganese dioxide (EMD), Chemical Manganese Dioxide (CMD) MnO, Mn2O3, Mn3O4, Manganese acetate, manganese borate, manganese carbonate, manganese chloride, manganese nitrate, manganese phosphates, manganese sulfate, potassium manganates Copper- disseminated sulfide deposit Duluth Complex Copper sulfide concentrate/matte Electrolytic copper metal Copper alloys (brass, bronze, gun metals, beryllium copper, copper nickel alloys). Copper sulfate, Copper acetates, Cuprous oxide, Cupric oxide (black copper oxide), Cupric chloride, Copper oxychloride, Cuprous chloride, Cupric nitrate, Copper cyanide, Copper soaps, Copper naphthenate Nickel-disseminated sulfide deposit Duluth Complex Nickel sulfide concentrate/matte/mixed hydroxide precipitate Electrolytic nickel metal Nickel alloys (stainless steel, superalloys) Nickel oxyhydroxide, Lithium nickel manganese cobalt oxide, Lithium nickel cobalt aluminium, nickel sulfate, Nickel chloride, nickel sulfamate, nickel oxide, nickel hydroxycarbonate, nickel nitrate, nickel diacetate, nickel hydroxide, nickel sulfide, nickel subsulfide NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 160 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Regional Resource/Value Chain Raw Material Feedstock Bulk Commodities Engineered Product Chemical compound Cobalt-disseminated sulfide deposit Duluth Complex Cobalt sulfide concentrate/matte/ mixed hydroxide precipitate Electrolytic cobalt metal lithium cobalt oxide, nickel- manganese-cobalt, nickel-cobalt- aluminum battery materials Cobalt(II) acetate, Cobalt(II) acetate tetrahydrate, Cobalt(II)carbonate, Cobalt carbonyl, Cobalt(II) chloride, Cobalt(II)hydroxide, Cobalt(II)naphthenate, Cobalt(II) nitrate, Cobalt(II,III) oxide, Cobalt(II) sulfate PGM-disseminated sulfide deposit Duluth Complex PGM sulfide concentrate/matte Platinum, Palladium Iridium, rhenium, rhodium, ruthenium ammonium chloroiridate, chloroirdic acid, iridium acetate, iridium trichloride ammonium tetrachloropalladate, palladium chloride, palladium nitrate, tetrammine palladium hydrogen carbon, tetrammine palladium nitrate, ammonium tetrachloroplatinate, ashby catalyst, chloroplatinic acid crystal,dihydrogen dinitrosulphatoplatinum, hexahydroxyplatinic acid, karstedt catalysts, platinum nitrate, perrhenic rhenium acid, ROPAC, rhodium acetate dimer/trimer Gold-disseminated sulfide deposit Duluth Complex Gold sulfide concentrate Gold dore, pure gold Gold Alloys ammonium tetrachloroaurate, gold chloride, gold bromide, potassium chloroaurate, sodium chloroaurate, NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 161 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance Appendix J: List of Historical Hydrometallurgical Studies at NRRI Appendix J provides a list of past publicly funded hydrometallurgical studies at NRRI. NRRI/RI-2022/10 – Opportunities offered by emerging hydrometallurgical technologies 162 Natural Resources Research Institute Innovative Research • Minnesota Value • Global Relevance 1. Metallurgical testing of copper-nickel bearing material from the Duluth gabbro progress summary (CMRL/TR-98-17). 2. Metallurgical testing of copper-nickel bearing material from the Duluth gabbro (NRRI/TR-98/29). 3. Characterization of residue from the pressure oxidation leaching of bulk copper-nickel sulfides from the Duluth gabbro (NRRI/TR-99/41). 4. Extraction of copper from chalcopyrite concentrates without sulfuric acid generation via chlorination - ii. Selective oxidation of chlorinated products (NRRI/TR-99/42). 5. Extraction metallurgy of copper from chalcopyrite concentrates 6. Without sulfuric acid generation via chlorination - iii. Integration of gaseous chlorination and selective oxidation (NRRI/TR-99/43). 7. 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