Browsing by Subject "membrane"

Now showing 1 - 6 of 6
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    Analysis of Bacterial Adhesion with Graphene Oxide-Modified PES Ultrafiltration Membranes
    (2019-06) Wuolo-Journey , Karl
    Given its potent biocidal properties, graphene oxide (GO) holds promise as a building block of anti-microbial surfaces, with numerous potential environmental applications. Nonetheless, the extent to which GO-based coatings decrease bacterial adhesion propensity, a necessary requirement of low-fouling surfaces, remains unclear. AFM-based single-cell force spectroscopy (SCFS) was used to show that coatings comprising GO nanosheets bonded to a hydrophilic polymer brush, mitigate adhesion of Pseudomonas fluorescens cells, while preserving GO’s intrinsic biocidal activity. This work demonstrated the simultaneous biocidal and low-adhesion GO coatings by grafting poly(acrylic acid) (PAA) to polyethersulfone (PES) substrates via self-initiated UV polymerization, followed by edge-tethering of GO to the PAA chains through amine coupling. The chemistry and interfacial properties of the unmodified PES, PAA-modified (PES-PAA), and GO-modified PES (PES-GO) substrates were demonstrated using ATR-FTIR, Raman spectroscopy, contact angle goniometry, and AFM to confirm the presence of PAA and covalently bonded GO on the substrates. Using SCFS, it was shown that peak adhesion force distributions for PES-PAA (with mean adhesion force F ̅Peak = -0.13 nN) and PES-GO (F ̅Peak = -0.11 nN) substrates were skewed towards weaker values compared to the PES control (F ̅Peak = -0.18 nN). The results show that weaker adhesion on PES-GO was due to a higher incidence of non-adhesive (repulsive) forces (45.9% compared to 22.2% over PES-PAA and 32.3% over PES), which result from steric repulsion allowed by the brush-like GO-PAA interface.
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    Fundamental Study of Microfiltration and Ultrafiltration of Liquid-borne Nanoparticles: Experiments and Models
    (2018-09) LEE, HAN DOL
    Access to clean water is a fundamental human need and one of the most important and essential elements to health. Despite the worldwide efforts to improve water purification systems, the World Health Organization reported that tens of millions of people are fatally sick and 1.6 million people die every year due to water-related diseases. The diseases are caused by excessive amounts of particulate contaminants, which are derived from industrial chemicals, agricultural runoff and natural pollutants. To reduce such toxic liquid-borne particles suspended in the aqueous environment, liquid filtration techniques using membrane filters have been considered one of the most effective treatments. The membrane techniques have been also widely used to produce a compound with a high level of purity in many industries such as semiconductor manufacturing, drug-related industry and wastewater treatment. The objectives of this thesis are to 1) explore characterization methods for the evaluation of liquid filtration membranes and 2) investigate particle retention behaviors of small nanoparticles through various membrane filters.
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    Measuring Binding Kinetics of Therapeutic Antibodies to Membrane Receptors Using Nanohole Array SPR Biosensors
    (2016-04) Jordan, Luke
    In the field of drug discovery, two important metrics of candidate drugs are their binding affinity and kinetics to target receptors. Dr. Moses Rodriguez and his colleagues at the Mayo Clinic have found monoclonal IgM antibodies exhibiting therapeutic effects for multiple sclerosis and amyotrophic lateral sclerosis in animal models, and therefore desired to obtain the kinetic profiles of these antibodies to their targets. Dr. Sang-Hyun Oh’s lab at the University of Minnesota specializes in designing and fabricating plasmonic devices, and have developed a nanohole array sensor coated with silicone dioxide which permits formation of cell mimicking supported lipid bilayers. The focus of this dissertation has been to build these devices and develop assays to measure the binding between these antibodies and receptors in cell extracts and supported lipid bilayers. The first antibody to measure was rHIgM22, which binds to myelin membrane. We did not know the receptor, so we used myelin extracts which would include the unknown receptors, and attached these particles to the sensor surface by passive immobilization. To reduce particle size into the sensor detection window, we extruded the particles through pores of known dimensions. After immobilization we measured binding with antibodies. Unfortunately, binding with rHIgM22 was undetectable, but a similar antibody, mouse IgM O4, which also binds to myelin and has a therapeutic effect, did bind consistently and gave KD, apparent = 2.6 ± 3.6 nM, ka = 2.5 ± 0.0l × 10^4 M^-1^s-1, and kd,slow = 6.6 ± 0.3 × 10^-5 s^-1. The second antibody to measure was rHIgM12, which binds to neuronal membranes. We found rHIgM12 binds to the gangliosides GT1b and GD1a, but not GM1. These gangliosides were incorporated into supported lipid bilayers (5 mol %) and binding to the antibodies was measured. Binding of rHIgM12 to GT1b gave KD, apparent = 24.8 ± 7.9 nM, ka = 2.19 ± 0.196 × 10^4 M^-1s^-1, and kd,slow = 4.72 ± 1.15 × 10^-4 s^-1. Binding of rHIgM12 to GD1a gave KD, apparent = 42.3 ± 20.6 nM, ka = 1.79 ± 0.516 × 10^4 M^-1s^-1, and kd,slow = 4.43 ± 1.38 × 10^-4 s^-1.
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    A modular technology for fermentative hydrogen production and capture from wastewater
    (2014-11) Sigtermans, Louis
    Despite the inherent chemical energy in wastewater, current wastewater treatment practices expend a considerable amount of energy to aerobically remove organic pollutants. Anaerobic fermentation of these dissolved organics to produce hydrogen could instead provide a positive energy output while delivering the ancillary benefit of lessening aeration demands for downstream treatment processes. A scalable and modular technology, based on the membrane-encapsulation of hydrogen-producing mixed consortia onto hollow fiber membranes for efficient hydrogen collection, was developed to produce and capture hydrogen from dissolved phase organics in wastewater. The membranes were tested in a continuously stirred tank reactor (CSTR) and monitored for hydrogen production and capture. The results showed that two different membrane polymer chemistries were successful in producing and capturing hydrogen from high-strength synthetic wastewater, with maximum captured yields of 25-50 mL/g hexose. Low available carbohydrate content, pH conditions, and leakage of microorganisms into and out of the membranes may have contributed to the failure of hydrogen production in trials using municipal wastewater. Batch tests of dairy manufacturing waste demonstrated the potential for future application of this technology for producing hydrogen from a real industrial wastewater.
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    Supporting data for Polymeric Microcapsules as Robust Mimics of Emulsion Liquid Membranes for Selective Ion Separations
    (2022-11-14) Werber, Jay R; Hillmyer, Marc A; Peterson, Colin H; Stipanic, Dean F; hillmyer@umn.edu; Hillmyer, Marc A; University of Minnesota Hillmyer Research Group
    Experimental and Modeling data in support of Published Article "Polymeric Microcapsules as Robust Mimics of Emulsion Liquid Membranes for Selective Ion Separations" in Environmental Science & Technology
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    Synthesis of Zeolite Nanosheets and Applications in Membranes and Adsorption Separation Processes
    (2016-05) Jeon, Mi Young
    In separation processes, desirable products with high purity are acquired at the expense of high energy cost procedures such as distillation. Alternative separation processes, such as zeolite membrane separation and adsorption processes, are promising to reduce the energy cost of production since zeolites can discriminate molecules on the basis of size/shape and functionality. Indeed, the high cost of zeolite membranes can be reduced by fabricating thin membranes with high throughput. High aspect ratio zeolite nanosheets can be used to fabricate zeolite membranes with high throughput on porous supports. To date, however, there is no published evidence that scientists have successfully achieved nanosheet synthesis under the direct hydrothermal treatment route. This dissertation documents a successful direct hydrothermal synthesis of zeolite nanosheets via seeded-growth—a process that leads to zeolite membranes that exhibit high performance on xylene isomer and butane isomer permeation. To the best knowledge, this is the first achievement to prepare zeolite nanosheets without complicated post treatment such as exfoliation and purification process (density gradient centrifugation). Extensive parametric studies are conducted in order to establish the optimal synthesis condition for high quality zeolite nanosheets. Additionally, in an effort to understand the mechanism of nanosheet formation, the sequential evolution of seed crystals into zeolite nanosheets is observed by time-resolved TEM imaging analysis. Keeping in mind that in the future polymers could be used to reduce the costs of membrane manufacture, the de-templation of MFI nanosheets without formation of aggregates is discussed in this dissertation. In addition to membrane applications, this dissertation probes the roles of hydrophobicity in ethanol adsorption when hydrophobic siliceous zeolites, and defective siliceous zeolite nanosheets with house-of-card architecture are provided as adsorbents. Vapor phase ethanol adsorption and aqueous phase ethanol adsorption are compared to investigate how water molecules affect ethanol adsorption onto siliceous zeolites in the aqueous phase.