Browsing by Author "Kim, Jun"

Now showing 1 - 7 of 7
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    A Polysulfone/Cobalt Metal–Organic Framework Nanocomposite Membrane with Enhanced Water Permeability and Fouling Resistance
    (American Chemical Society, 2022) Gil, Eva; Huang, Xiaochuan; Zuo, Kuichang; Kim, Jun; Rincón, Susana; Rivera, José María; Ranjbari, Kiarash; Perreault, François; Alvarez, Pedro; Zepeda, Alejandro; Li, Qilin; Nanosystems Engineering Research Center for Nanotechnology Enabled Water Treatment
    Ultrafiltration membranes are widely used in water and wastewater applications. The two most important membrane characteristics that determine the cost-effectiveness of an ultrafiltration membrane process are membrane permeability and fouling resistance. Metal–organic frameworks (MOFs) have been intensively investigated as highly selective sorbents and superior (photo) catalysts. Their potential as membrane modifiers has also received attention recently. In this study, a non-functionalized, water-stable, nanocrystalline mixed ligand octahedral MOF containing carboxylate and amine groups with a cobalt metal center (MOF-Co) was incorporated into polysulfone (PSF) ultrafiltration (UF) membranes at a very low nominal concentration (2 and 4 wt %) using the conventional phase inversion method. The resultant PSF/MOF-Co_4% membrane exhibited water permeability up to 360% higher than of the control PSF membrane without sacrificing the selectivity of the membrane, which had not been previously achieved by an unmodified MOF. In addition, the PSF/MOF-Co_4% membrane showed strong resistance to fouling by natural organic matter (NOM), with 87 and 83% reduction in reversible and irreversible NOM fouling, respectively, compared to the control PSF membrane. This improvement was attributed to the increases in membrane porosity and surface hydrophilicity resulting from the high hydrophilicity of the MOF-Co. The capability of increasing membrane water permeability and fouling resistance without compromising membrane selectivity makes the MOF-Co and potentially other hydrophilic MOFs excellent candidates as membrane additives.
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    Aqueous-Processed, High-Capacity Electrodes for Membrane Capacitive Deionization
    (American Chemical Society, 2018) Jain, Amit; Kim, Jun; Owoseni, Oluwaseye M.; Weathers, Cierra; Caña, Daniel; Zuo, Kuichang; Walker, W. Shane; Li, Qilin; Verduzco, Rafael; NSF Nanosystems Engineering Research Center, Nanotechnology-Enabled Water Treatment
    Membrane capacitive deionization (MCDI) is a low-cost technology for desalination. Typically, MCDI electrodes are fabricated using a slurry of nanoparticles in an organic solvent along with polyvinylidene fluoride (PVDF) polymeric binder. Recent studies of the environmental impact of CDI have pointed to the organic solvents used in the fabrication of CDI electrodes as key contributors to the overall environmental impact of the technology. Here, we report a scalable, aqueous processing approach to prepare MCDI electrodes using water-soluble polymer poly(vinyl alcohol) (PVA) as a binder and ion-exchange polymer. Electrodes are prepared by depositing aqueous slurry of activated carbon and PVA binder followed by coating with a thin layer of PVA-based cation- or anion-exchange polymer. When coated with ion-exchange layers, the PVA-bound electrodes exhibit salt adsorption capacities up to 14.4 mg/g and charge efficiencies up to 86.3%, higher than typically achieved for activated carbon electrodes with a hydrophobic polymer binder and ion-exchange membranes (5–13 mg/g). Furthermore, when paired with low-resistance commercial ion-exchange membranes, salt adsorption capacities exceed 18 mg/g. Our overall approach demonstrates a simple, environmentally friendly, cost-effective, and scalable method for the fabrication of high-capacity MCDI electrodes.
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    Electrodes for selective removal of multivalent ions through capacitive deionization
    (2023-08-29) Verduzco, Rafael; Jain, Amit; Kim, Jun; Li, Qilin; Zuo, Kuichang; Rice University; William Marsh Rice University; United States Patent and Trademark Office
    A method of forming an electrode for capacitive deionization includes depositing an slurry onto a substrate, wherein the slurry comprises a porous material, a first crosslinkable hydrophilic polymer, and a crosslinker for the first crosslinkable hydrophilic polymer; annealing the slurry deposited on the substrate to create a crosslinked porous layer on the substrate; depositing an solution comprising an ion-exchange material, a second crosslinkable hydrophilic polymer, and a crosslinker for the second crosslinkable hydrophilic polymer onto the crosslinked porous layer; and optionally annealing and/or drying the solution on the crosslinked porous layer.
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    Ion-transport Theory, Electrosorption Mechanism, and Application of Capacitive Deionization
    (2020-01-14) Kim, Jun; Li, Qilin
    To achieve a highly effective, easy to operate, electrical potential-driven water treatment process, three main areas have been investigated. First, a three-dimensional geometry-based equilibrium model is developed to fully describe the potential overlapping regimes from micro- to macro- pores in electrical double layers using the finite size of hydrated ions. Second, a membrane capacitive deionization (MCDI) is developed to achieve calcium-selective removal in an electrosorption process. Last, but not least, the ion-removal performance of a layered double hydroxide MCDI electrode is evaluated for the removal of lead ions in water.
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    Removal of calcium ions from water by selective electrosorption using target-ion specific nanocomposite electrode
    (Elsevier, 2019) Kim, Jun; Jain, Amit; Zuo, Kuichang; Verduzco, Rafael; Walker, Shane; Elimelech, Menachem; Zhang, Zhenghua; Zhang, Xihui; Li, Qilin; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment
    Technologies capable of selective removal of target contaminants from water are highly desirable to achieve “fit-for-purpose” treatment. In this study, we developed a simple yet highly effective method to achieve calcium-selective removal in an electrosorption process by coating the cathode with a calcium-selective nanocomposite (CSN) layer using an aqueous phase process. The CSN coating consisted of nano-sized calcium chelating resins with aminophosphonic groups in a sulfonated polyvinyl alcohol hydrogel matrix, which accomplished a Ca2+-over-Na+selectivity of 3.5–5.4 at Na+:Ca2+ equivalent concentration ratio from 10:1 to 1:1, 94 – 184% greater than the uncoated electrode. The CSN coated electrode exhibited complete reversibility in repeated operation. Mechanistic studies suggested that the CSN coating did not contribute to the adsorption capacity, but rather allowed preferential permeation of Ca2+ and hence increased Ca2+ adsorption on the carbon cathode. The CSN-coated electrode was very stable, showing reproducible performance in 60 repeated cycles.
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    Self assembled, sulfonated pentablock copolymer cation exchange coatings for membrane capacitive deionization
    (Royal Society of Chemistry, 2019) Jain, Amit; Weathers, Cierra; Kim, Jun; Meyer, Matthew D.; Walker, W. Shane; Li, Qilin; Verduzco, Rafael; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment
    Membrane capacitive deionization (MCDI) is a simple and low-cost method for brackish water desalination involving reversible electrosorption using high surface area, porous electrodes paired with ion-exchange membranes. Ion-exchange membranes improve charge efficiency and salt adsorption capacity by limiting the transport of co-ions and inhibiting faradaic reactions at the electrode surface. Effective ion-exchange membranes for MCDI should have high permselectivity and low ionic resistance, but there is typically a trade-off between these two properties. In this work, we studied partially sulfonated pentablock copolymer (sPBC) as a cation-exchange coating for MCDI electrodes. sPBC ion exchange coatings of varying ion exchange capacity (IEC, 1.0, 1.5, 2.0 meq g−1) and a range of casting solvent compositions (10–60 wt% n-propanol in toluene) were prepared. Transmission electron microscopy analysis of the membranes showed a morphological change from a micellar to lamellar and then to an inverse micellar structure with increasing polarity of the casting solvent. Water uptake and salt permeability increased with increasing IEC and casting solvent polarity over the entire range of conditions tested. MCDI device studies indicated that charge efficiency and salt adsorption capacity both increased with water uptake over a range of casting solvent compositions due to morphological changes in the sPBC film. This work demonstrates an effective solution-processible ion-exchange layer for MCDI using a self-assembling block copolymer and suggests that ideal ion-exchange coatings for MCDI should have high water uptake to minimize ionic resistance while at the same time maintaining a high charge density of fixed charged groups to achieve high permselectivity.
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    Simulating Transport and Adsorption of Organic Contaminants in 3D Porous Activated Carbon Block Media
    (2019) Kim, Jun; Morgott, Amanda; Wu, Ziqi; Hopaluk, Liane; Miles, Michael; Stoner, William; Li, Qilin
    To evaluate the organic contaminants removal performance of hollow cylindrical block-shaped porous activated carbon media, COMSOL Multiphysics® simulation software with Chemical Engineering module was used. The study clearly demonstrates how each organic compound in a steady-state fluid is dynamically transported in the three-dimensional porous media and removed by adsorption. The simulated adsorption results are compared to the experimental test data for validation. Axisymmetric geometry in COMSOL gives better simulation accuracy and faster computation than full three-dimensional geometry due to higher element quality and lower volume/area ratio. Based on 5% breakthrough (95% removal) line, the COMSOL simulations have only 0.9-2.9% discrepancy from the actual data, while a classical two-dimensional rapid-small-scale column test (RSSCT) model method has 39.8-782.2%. The COMSOL Multiphysics® model used in this transport/adsorption study successfully demonstrated not only flow patterns in the modulated reactor but also chemical concentration changes in the full-scale porous adsorbent structure.