Browsing by Author "Jain, Amit"

Now showing 1 - 6 of 6
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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 Exchange Polymer Coated Electrodes for Selective Electrosorption Based Water Softening Applications
    (2020-04-23) Jain, Amit; Verduzco, Rafael
    Electrosorption is a developing water treatment method and operates by applying an electrical potential between two porous electrodes. In membrane based electrosorption system, ion-exchange membranes are placed in front of each electrode to prevent the passage of co-ions, resulting in enhanced salt removal and charge efficiencies. However, currently not many electrosorption systems exist which can selectively remove specific ions. Membrane based selective electrosorption systems that could selectively remove target ions can be useful for various water treatment applications. For example, produced water treatment requires selective removal of scale forming ions (Ba2+, Ca2+, Sr2+, SO42-) to prevent scale deposition in various piping and equipment surfaces. Furthermore, if using an electrosorption approach, ion selective approach would be more energy efficient. In this work, in the first stage, ion exchange polymer coated electrodes were developed, and a high salt removal and energy efficiency performance was obtained. In the second stage, a novel sulfonated polymer (PEDOT:PSS) coated electrode for selective electrosorption was developed. Ion selective electrosorption tests were conducted using a mixed salt solution consisting of CaCl2 and NaCl. Furthermore, applied voltage, feed flow rate and composition were varied to analyze their effect on the selectivity performance. The test results indicate that with this novel electrosorption system a highest Ca2+/Na+ selectivity of 8.21 ± 2.88 at 0.6 V could be achieved.
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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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    Sulfonated polymer coating enhances selective removal of calcium in membrane capacitive deionization
    (Elsevier, 2022) Nnorom, Njideka C.; Rogers, Tanya; Jain, Amit; Alazmi, Abdullah; Elias, Welman Curi; DuChanois, Ryan M.; Flores, Kenneth R.; Gardea-Torresdey, Jorge L.; Cokar, Marya; Elimelech, Menachem; Wong, Michael S.; Verduzco, Rafael; NSF Nanosystems Engineering Research Center, Nanotechnology-Enabled Water Treatment
    There is a need for membranes and processes that can selectively separate target ions from other similar ionic species. Recent studies have shown that electrified processes for ion removal such as membrane capacitive deionization (MCDI) and electrodialysis (ED) are selective towards specific ionic species, but selectivities are generally limited. Here, we demonstrate that an ion-selective polymer coating can significantly enhance ion selectivities for MCDI processes. We focused on the preferential removal of Ca2+ over Na+ and used the conductive and sulfonated polymer poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) as a model selective ion-exchange coating. We first measured the permeability of Ca2+ and Na+ in freestanding PEDOT:PSS membranes of varying crosslink density and found that the permeability of Ca2+ was six times greater than that for Na+ in optimized membranes. Next, we used PEDOT:PSS in an MCDI process by depositing thin PEDOT:PSS coatings on top of composite electrodes. We found that the PEDOT:PSS coatings significantly enhanced the preferential permeability of Ca2+ over Na + relative to unmodified electrodes and produced a preferential removal as high as 8:1 on a molar basis. This work demonstrates a new approach to enhance selective ion removal in MCDI and other electro-driven ion separation processes.