Browsing by Subject "Silica"

Now showing 1 - 20 of 22
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    3D Printed Biocatalytic Silica Hydrogel Flow-Through Reactor For Atrazine Degradation
    (2017-06) Han, Ryan
    One of the most heavily used herbicides in the world, atrazine, provides a serious environmental challenge that we face presently. Atrazine has been consistently applied to farms due to its proven ability to remove broadleaf weeds, allowing for increased yields of corn crops, which is necessary to feed an ever-growing world population. However advantageous the use of atrazine is, toxic effects have been identified when humans ingest atrazine. Also, the high mobility of atrazine during run-off events after application to fields allows atrazine to be easily incorporated into water systems around agricultural land, creating a large-scale health and environmental problem as the increased atrazine concentrations negatively impact human health when ingested as well as ecological disturbances when affecting local algal communities. The presented work investigates the application of 3D printing as an approach to solving this significant problem. We hypothesize that with direct-write 3D printing of biologically active, printed materials to perform the bioremediation of atrazine, may enhance bioremediation capacity compared to conventional methods by utilizing the near limitless rapid design flexibility intrinsic to 3D printing to allow fabrication of structures with high surface area to volume ratio (SA:V), yielding lower diffusion length scales that allow improved encapsulated biocatalyst usage. We introduce a novel 3D printing method to produce application specific complex 3D geometries from a sol-gel based silica material with encapsulated biocatalysts. To produce a bioactive material with the incorporation of biocatalysts, silica hydrogel formed through a sol-gel process was used as the ink base. E. coli genetically engineered to overexpress the AtzA enzyme, which degrades the toxic herbicide atrazine to the non-toxic compound hydroxyatrazine, were encapsulated within the silica-based ink. This process leverages the strong mechanical properties, high chemical transport properties, and biocompatibility of the silica base material along with the full material customization, precision in spatial deposition, and design flexibility intrinsic to the 3D printing process to overcome obstacles that hinder the use of bioactive materials within conventional 3D printers (material constraints and biologically deadly processing). The developed 3D printer ink was characterized in terms of gelation kinetics, mechanical properties, cell distribution, and degradation capability. Results confirmed that the 3D printed AtzA biocatalysts sustained biodegradation ability through the removal of atrazine and production of hydroxyatrazine through batch reactor experiments. High SA:V geometries produced through 3D printing also showed improved degradation efficiency by encapsulated biocatalysts. This allowed for an advantage over previously presented work because by providing high SA:V structures, the atrazine did not have to diffuse over long length scales until it was biotransformed within a bacterial cell. Structures with low SA:V were shown to decrease in degradation efficiency because as the atrazine concentration gradient decreased, only the cells closer to the surface would perform the biotransformation of atrazine, the cells located more centrally would not contribute to the degradation. Therefore, with a decrease in diffusion length to all encapsulated biocatalysts, the overall function of the encapsulated population as the concentration of atrazine dropped would be improved over past methods. Additionally, a flow-through bioreactor was designed, simulated, and experimentally tested. ANSYS reaction-flow simulations were completed to determine experimental flow rates necessary to positively identify atrazine degradation in the flow-through bioreactor. Finally, atrazine degradation was proven in flow-through experiments at an inlet flowrate of 1 ml/min. Observed atrazine degradation equated to 15 ± 5% of overall inlet concentration atrazine. Through this work, we have shown as a proof of concept that 3D printed silica-encapsulated biocatalysts sustain the function to degrade an environmental pollutant. This work may be expanded further via the incorporation of multiple types of biocatalysts encapsulated in an organized pattern (multiple different 3D printer inks printed in a designed pattern) that enhances biotransformation and transport of products between the multiple biocatalysts. In addition, this work may be applied to advance fields where complex geometries of encapsulated biocatalysts are necessitated, which may include the fields of pharmaceutical, medical, environmental, and materials science.
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    Block Copolymer and Silica Modified Epoxy Structural Adhesives
    (2021-06) Pang, Vincent
    Block copolymers have been studied extensively as toughening agents for epoxies over the past two decades, where most work has been focused on improving the bulk properties of epoxies. However, epoxies are commonly utilized in applications where bulk properties are only part of the story. We begin to address this by studying block copolymer modified epoxies as structural adhesives and exploring the impacts of these additives on adhesion strength. Poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) block copolymers were synthesized and dispersed in epoxy formulations, forming spherical micelle and bilayer vesicle structures. Both morphologies led to significant increases in critical strain energy release rate, GIc, over the neat epoxy with no reduction in the elastic modulus. Spherical micelle modified epoxy adhesives showed up to a 46% enhancement to single-lap-joint shear adhesion strength. Electron micrographs of the fracture surfaces indicated that micelle cavitation plays a role in both the toughening and adhesion strength enhancements of epoxies. In contrast, a 28% reduction in adhesion strength was observed in the bilayer vesicle modified epoxies.Recently, there has also been a growing interest in studying epoxy composites with both rubbery and rigid particle modifiers. We explore this by extending our understanding of block copolymer toughening to composites containing both block copolymer and silica nanoparticles. Nanosilica and spherical micelle-forming PEP-PEO modifiers were dispersed both individually and together in epoxy formulations. The nanosilica and PEP-PEO modifiers formed uniform dispersions when added individually in the matrix but led to limited aggregation of nanosilica particles when added together. Incorporating nanosilica in neat and block copolymer modified epoxies led to increases to both fracture toughness and elastic modulus. Combining both additives led to additive toughening beyond that obtained with the individually modified epoxies. The extent of these improvements also increased with nanosilica loading up to 25 wt%. Electron micrographs of the failure surfaces revealed both micelle cavitation and nanosilica debonding occurring in concert. These findings were taken further in a final study on how silica and block copolymer modified epoxy adhesives impact toughness and adhesion strength. Micelle-forming PEP-PEO and various types of silica particle modifiers were again dispersed in epoxy formulations. All modifiers were well dispersed when added individually to the matrix. When added together, microsilica particles remained well-dispersed, in contrast to the partial aggregation observed with nanosilica. Increases to both fracture toughness and elastic modulus were observed when all types of silica were incorporated, without significant effects from silica particle size or surface functionalization. Adhesion strength was increased by approximately 50% when block copolymer was added and was not affected by the silica. Overall, the incorporation of silica improved both elastic modulus and fracture toughness without compromising the adhesion strength enhancement from block copolymer micelles.
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    Cell Response to Silica Gels with Varying Mechanical Properties
    (2013-07) Lefebvre, Molly
    Sol-gel encapsulation has a variety of applications in biotechnology and medicine: creating biosensors, biocatalysts, and bioartificial organs. However, encapsulated cell viability is a major challenge. Consequently, interactions between cells and their 3D microenvironment were studied through rheological, metabolic activity, and extraction studies to aid in the development of new gel protocols. The cells were encapsulated in variations of three silica sol-gels with varying stiffness. It was hypothesized that the cell viability and the amount of extracted cells would depend on gel stiffness. For two gels, there was no apparent correlation between the gel stiffness and the cell viability and extracted cell quantity. These gels did strongly depend on the varying gel ingredient, polyethylene glycol. The third gel appeared to follow the hypothesized correlation, but it was not statistically significant. Finally, one gel had a significantly longer period of cell viability and higher quantity of extracted cells than the other gels.
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    Correlation of Metallurgical Testing of Mine Samples to Plant Feed and Concentrate
    (University of Minnesota Duluth, 2007) Benner, Blair R
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    Critical considerations in development of mesoporous silica nanoparticles for biological applications.
    (2012-04) Lin, Yu-Shen
    In the past ten years, mesoporous silica nanoparticles have been some of the hottest materials investigated for biomedical use. Mesoporous silica nanoparticles are size-controllable and discrete particles with high surface area, large pore volume, and easy surface modification properties. These unique characteristics make mesoporous silica nanoparticles promising for biological applications. Although there is extensive literature precedent for the synthesis and applications of mesoporous silica nanoparticles, there are several critical issues resulting in limited use of multifunctional mesoporous silica nanoparticles in vitro or in vivo. For example, the large particle size (> 100-nm-diameter) and poor particle stability (aggregation) result in rapid uptake by the reticuloendothelial system, a portion of immune system which removes the nanoparticles from circulation before they reach their tumor target. Another hurdle is the possible unintentional toxicity of such nanoparticles. If the designed mesoporous silica nanoparticles cause unintentional damage to benign cells or healthy tissue and organs, their use will be greatly limited in therapeutic applications. Prior to in vivo animal experiments, unintentional cytotoxicity must be minimized and well studied. Based on the critical considerations described above, an ideal mesoporous therapeutic should possess the following characteristics prior to in vivo studies: (1) small size (<50 nm); (2) high surface area; (3) high stability; and (4) minimal unintentional cytotoxicity. Chapter One reviews the development and use of mesoporous silica nanoparticles for biomedical use. Various components have been incorporated into mesoporus silica nanoparticles to yield various functionalities, like controlled drug release, targeting, and multimodal imaging for diagnosis. With more and more complex designs for mesoporous silica nanoparticles, practical considerations for in vivo use must be taken into account. Chapter Two describes our novel method to synthesize highly stable, redispersible, and small mesoporous silica nanotherapeutics. This chapter discusses the particle stability of bare and modified mesoporous silica in various biological media. Critical synthetic parameters including introduction of hydrophilic and hydrophobic organosilanes and hydrothermal treatment are key to synthesize ultrastable and redispersible mesoporous silica nanoparticles. Chapter Three examines the cytotoxicity of mesoporous silica nanoparticles to human RBCs, mouse mast cells, and human endothelial cells using (1) a hemolysis assay, (2) an electrochemical assay of cell function and (3) a microfluidic device. The experimental results reveal that mesoporous silica nanoparticles have lower adverse effects on RBCs and mast cells than their similarly sized nonporous counterparts. In addition, shear stress effects on the cytotoxicity of unmodified mesoporous silica will be discussed. In Chapter Four, a novel one-pot synthesis route was developed to fabricate size-tunable multifunctional mesoporous silica nanoparticles. Based on the experience from improving bare mesoporous silica stability, the hydrothermally assisted organosilane modification method was applied to improve the particle stability, T2 relaxivity stability, and acid resistance of magnetic mesoporous silica nanoparticles. In the last part of my research work, Chapter Five investigates cytotoxicity of new carbon nanomaterials, graphene oxide and graphene in human erythrocytes and skin fibroblasts. The cytotoxicity results show that the physico-chemical properties, including the particle size, exfoliation extent, oxygen content, and aggregation state of graphene oxide and graphene greatly influence their cytotoxicity. This collaborative work also inspired me to consider a possible future direction involving the incorporation of graphene oxide or graphene into mesoporous silica nanoparticles to control drug release via a heat-driven route. To conclude, Chapter Six reviews my thesis work and highlights the advances I have made in the fields of nanomedicine and nanotoxicity. In addition, possible future directions are also described.
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    Design of Silica-Collagen Nanocomposite for Corneal Replacement
    (2015-09) DiVito, Michael
    The cornea is the most commonly transplanted tissue in the United States. Globally, corneal diseases are the second leading cause of blindness. Due to strict FDA regulations, lack of eye banking facilities, and other factors which limit the supply of donor tissue, designing an artificial cornea made of readily available materials is of great interest. The synthetic constructs that are currently clinically available in the United States have had moderate success, but biocompatibility issues such as stromal melting and epithelial defects are still common. When considering a potential material for corneal replacement, it must meet the design criteria of the normal functioning cornea. The relevant design criteria can be broken down into three main groups: optical behavior, biomechanical properties, and biocompatibility. The presented work proposes silica-collagen nanocomposites as a viable candidate material to meet these design criteria. A bottom-up approach starting from the molecular level is utilized to modify the surface chemistry and physical properties of collagen fibrils. In doing so, methodologies are presented which allow for fine-tuning of optical, biomechanical, and biodegradation behavior. The first part of this work validates the theory that light scattering of collagen hydrogels is heavily dependent on the change in the material’s index of refraction over length scales comparable to the wavelength of incident light. This work shows that light scattering of collagen hydrogels can be minimized by a rapid neutralization technique, and by the addition of nanocrystalline cellulose. Additionally, collagen hydrogels with embedded magnetic nanowires can be polarized to form an aligned fibril microstructure and show an increase in light transmission. The second part of this thesis characterizes the mechanical and optical behavior, as well as the biocompatibility of silica-collagen nanocomposites. This work shows that a copolymerization method can be used to make implants which have improved biomechanical properties (when compared to pure collagen hydrogels) and can be re-epithelialized in an ex vivo rabbit model. Additionally, an improved two-step process for silica deposition onto collagen fibrils is presented. This new method shows that poly-L-lysine can be used to induce a uniform silica shell around collagen fibrils in the absence of large silica aggregates. This new method increases mechanical stiffness and enzymatic degradation resistance without producing any additional light scattering in the material. Silica-collagen nanocomposites show great potential in the context of corneal replacement. The methods developed and results presented here can be useful for improving any collagen-based corneal replacement, as well as in other applications such as drug delivery and silica nanoparticle templating.
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    Encapsulation of proteins and cells in silica nanoporous materials
    (2011-11) Reategui, Eduardo
    My dissertation presents fundamental and practical scientific contributions. I demonstrated the versatility of the sol-gel processing technology for the study of the basic science behind water and protein structure under confinement, and for the development of novel biotechnology and biomedical engineering applications based on cell encapsulation in nanoporous silica gels.For the basic science studies of my dissertation, silica nanoporous gels were used to investigate the kinetic and thermodynamic transitions of water under confinement. I demonstrated a direct correlation between the structure of confined water and the secondary structure of proteins in a wide range of temperatures (- 196C to 95C). I showed qualitatively that the incorporation of a highly hydrogen bonding osmolyte contributed to improve the thermal stability of encapsulated proteins by a mechanism based on prevention of adsorption at the surface of the nanoporous silica material. For the practical contributions of my dissertation, I developed two novel applications relevant to the biotechnology and biomedical engineering fields. These applications were based on the encapsulation of prokaryotic and eukaryotic cells in silica nanoporous gels. First, I developed a highly selective and efficient biodegradation platform for the removal of an herbicide, atrazine, from contaminated water. In the second application, I invented a cell capture and isolation methodology that was successfully tested as a cancer cell isolation tool from mixed populations of eukaryotic cells (normal and cancer cells). Miscellaneous applications were also investigated such as encapsulation as a means of cryopreservation of mammalian and algae cells, and were incorporated in the Appendices of this thesis.
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    Final Report: Shallow vs. Deep Bed Sintering
    (University of Minnesota Duluth, 2010) Englund, David J
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    Investigation into Production of Iron Ore Concentrates with less than 3 percent Silica from Minnesota Taconites Report Two · Erie Concentrate
    (University of Minnesota Duluth, 1991-06) Benner, Blair R; Bleifuss, Rodney L
    The pellets produced by Minnesota taconite companies generally contain between 4.0 and 7.0 percent silica. These silica levels were established initially by the concentratability of the ore, that is, its response to closed circuit ball mill grinding and magnetic concentration. Those operations that had taconite that was easy to concentrate generally produced lower silica pellets. As processing technology improved and it became possible to achieve lower silica levels constraints imposed by the blast-furnace operation became limiting. These constraints related primarily to sulphur and alkali levels in the furnace which control both the volume and chemistry of the furnace slag. Because the trend in blast-furnace practice has been to move toward lower slag volumes, pellets with lower silica levels have become more desirable. Recent extensive installation of external hot metal desulphurization facilities at many steel works allows even lower slag volumes. The basic driving force to go to lower slag volumes is the cost and availability of high quality metallurgical grade coke and related environmental problems. The recent move to produce fluxed pellets has made lower pellet silica levels more attractive because of the lower palletizing costs related to both the lower flux addition and higher production rates with a lower silica content. A common target silica level in fluxed pellets is now about 4.0 percent. A 4.0 percent silica pellet requires a concentrate containing between 3.7 and 3.9 percent silica depending upon bentonite addition levels. This lower silica level has been accomplished in some plants by the use of fine screens, while other plants require the use of silica flotation. The lower silica level has been accomplished at a relatively small incremental cost, generally less than $0.50 per ton. With increasing pressure from the blast furnaces for lower-silica pellets to reduce coke consumption, concentrate silica levels on the order of 3.0 percent may be common in the future. In addition to the need to produce a lower silica blast-furnace feed, there is a potential need to produce even lower silica concentrates, below 3.0 percent, as feed stock for direct steelmaking. Worldwide the current research emphasis is on the development of a coal-based direct-steelmaking process to replace the conventional two step, blast furnace-basic oxygen furnace, process. Most of the current prototype direct steel making processes would benefit from a lower silica feed. These low silica levels will require increasingly complex and expensive secondary treatment of normal magnetic concentrates which exceed the capability of current taconite processing flowsheets. The purpose of this test program is to establish the lower silica limits that can be achieved by current technology for various Minnesota taconites and gain a preliminary indication of the cost.Because the magnetite concentrates produced by different taconite plants range significantly in terms of their size-silica relationships the program included three different concentrate sources for evaluation. Major differences will exist between concentrates produced in a fully autogenous grinding system and those produced in a conventional rod mill-ball mill circuit in which the ball mills are closed with hydrocyclones and/or a combination of hydrocyclones and fine screens. There are also differences in the nature of the siliceous gangue minerals in the various operations. The concentrates from the western Mesabi range contain quartz and low- grade metamorphic iron silicates such as minnesotaite, stilpnomelane, and talc and iron carbonates. The concentrates from the east Mesabi metamorphosed iron formation contain high grade metamorphic iron silicates such as cummingtonite, grunerite, and fayalite as well as quartz. The type of gangue mineral greatly affects the ability to upgrade the concentrates by silica flotation. The purpose of this test program is to determine the lowest silica content that it is technically possible to produce from three different concentrate sources representing the east Mesabi metamorphosed iron formation (Erie), the unmetamorphosed central range produced in a rod mill and ball mill circuit (Minntac), and the unmetamorphosed western Mesabi produced in an autogenous milling circuit (Hibtac). Sufficient data were collected to allow preliminary cost estimates to be made at several silica levels. The cost estimates will be based on reagent consumption, regrind power and metal requirements, and iron recovery. This report contains all of the information obtained on the Erie samples. This includes the results of the initial characterization studies, basic bench scale beneficiation test results, pilot plant flotation data, and the results of the secondary and tertiary treatment of bulk flotation froth to improve overall iron recovery.
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    Occupational Health Assessment of Crystalline Silica and Respirable Dust Exposure in Taconite Mine Workers in Northeastern Minnesota
    (2016-01) Odo, Nnaemeka
    Introduction and objectives: This research effort investigated three study areas. Firstly, the impact of ATS/ERS “acceptability” and “repeatability” criteria for spirometry on the estimates of restrictive ventilatory defect was assessed in a population of taconite miners. The estimates of restrictive ventilatory defect were made using three different pulmonary function tests (spirometry, alveolar volume and diffusing capacity). Secondly, the association between cumulative silica exposures in taconite mining and non-malignant respiratory disease (NMRD) outcomes was evaluated. Cumulative silica exposure was determined using current and historical exposure measurements while health outcomes were assessed from a cross-sectional screening study of taconite mine workers. The final study area explored the joint effects of silica dust, elongate mineral particles (EMP) and non-silica respirable dust on exposure-NMRD association in miners, also using health outcomes from cross-sectional screening. Methods: A survey of current and former taconite workers was undertaken in 2010-2011. Miners were screened with a questionnaire that focused on occupational and medical history, followed by clinic examinations including lung tests (spirometry, chest x-rays). Current and former workers who completed the survey and performed all three pulmonary function tests (spirometry, alveolar volume and diffusing capacity) were assessed (n=1084). We applied American Thoracic Society (ATS/ERS) acceptability criteria for all tests and categorized subjects into groups according to whether they fully met, partially met, or did not meet acceptability criteria for spirometry. Obstruction and restriction were defined utilizing the lower limit of normal (lower five percent) for all tests. Mixed ventilatory defect groups were also described indicating coexisting obstructive and restrictive ventilatory defects. When using alveolar volume, restriction was identified after excluding obstruction. Occupational exposure assessment was performed which measured over 1,500 onsite samples for respirable dusts including silica in 28 major job functions in taconite mining. Historical exposures to dusts were estimated with data obtained from prior onsite exposure measures by existing mining operations, and from Mine Safety and Health Administration (MSHA) data for those same operations. Individual work histories from completed questionnaires were used to determine the length of time worked (years) in these jobs. Cumulative silica exposure ((mg/m3)-years) was estimated as a product of time worked and year-specific silica dust measures for each of 28 unique job functions. Forced vital capacity (FVC) less than lower limits of normal (LLN) for age, height, race and gender was used to determine spirometric restriction in participants with “usable” spirometry. Chest x-rays were evaluated using ILO criteria for any evidence of parenchymal abnormalities of 1/0 or greater and for pleural abnormalities suggestive of pneumoconiosis by two blinded B-readers, with a third reader to arbitrate disagreements. Prevalence ratios of association (PR), with 95% confidence intervals (CI), between silica exposures and lung disease outcomes were estimated using Poisson regression models. Regression models were adjusted for smoking, gender, age, BMI and estimation of commercial asbestos exposure. The last area of study focused on exploring possible associations between combined silica, EMP, and non-silica respirable dust exposures and NMRD prevalence. Non-silica respirable dust includes iron oxides and particulate matter (PM) generated from mining and processing the ore. PRs of association with NMRD outcomes were calculated each for silica, EMP and non-silica respirable dust as continuous variables. Using dichotomous exposures (high versus low levels determined by the median cumulative exposure), we then estimated the PRs for silica NMRD-association within strata of EMP and non-silica dust. Relative excess risk due to interaction (RERI), attributable proportions (AP) and synergy index (SI) with 95% CIs, were then estimated to assess interaction on the additive scale. On the multiplicative scale, separate models each were used for assessing silica-EMP interaction and a second model for silica-non-silica interaction, using corresponding product terms within the models. Results: Estimating restrictive ventilatory defect Only 519 (47.9%) tests fully met ATS/ERS spirometry acceptability criteria. Within this group, 5% had obstruction and 6%, restriction on spirometry. In contrast, among all participants (N=1,084), 16.8% had obstruction, while 4.5% had restriction. Alveolar volume restriction showed similar results in all groups after obstruction was excluded. Impaired gas transfer (Diffusing capacity) was identified in less than 50% of restriction identified by either spirometry or alveolar volume. BMI was significantly related to spirometric restriction in all groups. Association between silica and nonmalignant respiratory disease Spirometric restriction occurred in 7.2%; chest x-ray parenchymal abnormalities occurred in 5.4%; chest x-ray pleural abnormalities consistent with pneumoconiosis were observed in 16.8%; and symptoms of shortness of breath (dyspnea on exertion) occurred in 11.4% of the study population. Silica exposure was associated with restrictive ventilatory defect prevalence (PR= 1.40; 95%CI=1.08-1.81) and the prevalence of parenchymal changes on chest x-ray (PR= 1.30; 95% CI=1.00-1.69). Exploring respirable dusts joint effects in taconite mining Assessments for silica-EMP and silica-non-silica additive and multiplicative interactions were not statistically significant. The exposure with significant association with health outcome (on spirometry), of the three exposures studied, was silica. Conclusions: Population estimates of restriction using spirometry or alveolar volume varied by spirometric acceptability criteria. Other factors identified as important considerations in the estimation of restrictive ventilatory defect included increased BMI and gas transfer impairment in a relatively smaller proportion of those with spirometric restriction. Spirometric assessment suggested a 40% increase in association with NMRD prevalence for workers given silica exposure. Silica exposure was also associated with parenchymal chest x-ray findings. However, these associations were dependent on the approach for estimating exposure. The presence of EMP and non-silica dust did not significantly modify the relationship between silica exposure in taconite mining and NMRD on either the additive or the multiplicative scales. Overall, these insights are important when interpreting population-based physiological data in occupational settings and understanding lung disease associations of silica and other respirable dust exposures.
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    Potential Value Added Products from the Minnesota Ilmenite Deposits
    (University of Minnesota Duluth, 2002-10) Benner, Blair R; Niles, Harlan B
    As part of the University of Minnesota’s ongoing support for the development of ilmenite deposits located within the Duluth complex, the University’s Permanent Trust Fund sponsored a project by the Coleraine Minerals Research Laboratory to determine if valued added products could be produced from the ilmenite deposits and to determine if ilmenite recovery could be increased. A previous study sponsored by the Minerals Coordinating Committee indicated that using high pressure rolls in place of a rod mill to grind the ilmenite increases TiO2 recovery by about 10 percent. The major loss of TiO2 (about 25 %) was associated with the removal of magnetite by magnetic separation after spiral concentration. The objective of this program was to determine if the magnetic portion of the spiral concentrate could be upgraded to make a concentrate suitable for either blast furnace pellet feed or DRI feed. During upgrading of the magnetic portion, non-magnetic materials should contain the bulk of the ilmenite, and they would also be upgraded to determine the potential for additional ilmenite recovery. Initial liberation grinds and Davis tube tests on the spiral magnetic concentrate indicated that grinding and magnetic separation alone could not upgrade the material sufficiently. Standard silica flotation on the ground and magnetically separated material did not provide significant upgrading. The best concentrate produced contained 58.84 percent iron, 6.66 percent TiO2, and 5.74 percent silica. Perhaps this material could be used in the iron nugget process. Amine flotation, fatty acid flotation and WHIMS were used to recover TiO2 from the non-magnetic portion of the reground spiral magnetic concentrate. Only fatty acid flotation of the ilmenite showed any potential for recovering additional ilmenite at grade. Additional test work on the use of silicate depressants is needed. Elutriation tests on size fractions indicated that grinding to finer than 200 mesh is needed for liberation of the ilmenite from the silicate gangue. While the previous test work showed increased TiO2 recovery in the spiral nonmagnetic fraction, no work was conducted on upgrading that material to determine if the increased recovery could be carried through to a final concentrate. Therefore, bench scale electrostatic separator tests were run on the spiral non-magnetic fraction produced in the previous project. The electrostatic tests indicated that both grade and recovery could be obtained.
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    Production of Low-Silica Concentrates from Mesabi Taconite
    (University of Minnesota Duluth, 1993) Benner, Blair R
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    Production of Low-Silica Concentrates from Mesabi Taconite – Report 2 Column Flotation
    (University of Minnesota Duluth, 1993) Benner, Blair R
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    Production of Two Percent Silica Concentrate for Cyprus Northshore Mining Company
    (University of Minnesota Duluth, 1994) Benner, Blair R
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    A Purpose Oriented Magnetic Separator: Skimmer
    (University of Minnesota Duluth, 2005) Ersayin, Salih
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    Screen Performance Optimization : Part 28: Derrick Corporation
    (University of Minnesota Duluth, 2003-09-03) Larson, Thomas R
    The Derrick Corporation participated in this project in a slig~1tly different way. Rather than ship machines to the Coleraine Minerals Research Laboratory pilot plant, two drums of each sample were shipped to the Derrick Corporation laboratory in Buffalo, New York. In addition, Derrick requested that two machines be tested rather than one, so that a previous technology could be compared with the new. Both changes in protocol were approved by the Minnesota Department of Natural Resources, for which acknowledgment and thanks are certainly due. Using the feed samples, Derrick staff optimized the separations in an initial series of tests. From these tests, the optimum solids, panel sizes, and other relevant operating conditions were selected before formal test sequences began. The scope of work for this project follows the pattern set in Part 1, in which five tests were completed on each of two feed samples, one from Hibbing Taconite, and one from Northshore Mining. In this case, the number of tests is doubled again to apply to two different screening machines. Part 2 also includes silica and magnetic iron assays on head samples as well as on each size fraction. The separation criteria for these tests was to achieve a split near 100 microns for the Hibbing Taconite material, and an undersize grade close to 90% -325 mesh for the Northshore Mining material. After the panels were selected and other operating issues were decided, the formal test sequence involved using two values for feed rate and two values of feed solids that were just higher and just lower than in the initial tests. The idea was to bracket the optimum separation and measure the variation in screen performance as these two parameters varied. For each machine sample combination, the four tests were completed in a 2x2 pattern, and a fifth test was a repetition of one of the first four in order to measure experimental error.