Browsing by Author "DuChanois, Ryan M."

Now showing 1 - 4 of 4
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    Membrane Materials for Selective Ion Separations at the Water–Energy Nexus
    (Wiley, 2021) DuChanois, Ryan M.; Porter, Cassandra J.; Violet, Camille; Verduzco, Rafael; Elimelech, Menachem; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT)
    Synthetic polymer membranes are enabling components in key technologies at the water–energy nexus, including desalination and energy conversion, because of their high water/salt selectivity or ionic conductivity. However, many applications at the water–energy nexus require ion selectivity, or separation of specific ionic species from other similar species. Here, the ion selectivity of conventional polymeric membrane materials is assessed and recent progress in enhancing selective transport via tailored free volume elements and ion–membrane interactions is described. In view of the limitations of polymeric membranes, three material classes—porous crystalline materials, 2D materials, and discrete biomimetic channels—are highlighted as possible candidates for ion-selective membranes owing to their molecular-level control over physical and chemical properties. Lastly, research directions and critical challenges for developing bioinspired membranes with molecular recognition are provided.
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    Precise Cation Separations with Composite Cation-Exchange Membranes: Role of Base Layer Properties
    (American Chemical Society, 2023) DuChanois, Ryan M.; Mazurowski, Lauren; Fan, Hanqing; Verduzco, Rafael; Nir, Oded; Elimelech, Menachem; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT)
    Separation of specific ions from water could enable recovery and reuse of essential metals and nutrients, but established membrane technologies lack the high-precision selectivity needed to facilitate a circular resource economy. In this work, we investigate whether the cation/cation selectivity of a composite cation-exchange membrane (CEM), or a thin polymer selective layer on top of a CEM, may be limited by the mass transfer resistance of the underlying CEM. In our analysis, we utilize a layer-by-layer technique to modify CEMs with a thin polymer selective layer (∼50 nm) that has previously shown high selectivity toward copper over similarly sized metals. While these composite membranes have a CuCl2/MgCl2 selectivity up to 33 times larger than unmodified CEMs in diffusion dialysis, our estimates suggest that eliminating resistance from the underlying CEM could further increase selectivity twofold. In contrast, the CEM base layer has a smaller effect on the selectivity of these composite membranes in electrodialysis, although these effects could become more pronounced for ultrathin or highly conductive selective layers. Our results highlight that base layer resistance prevents selectivity factors from being comparable across diffusion dialysis and electrodialysis, and CEMs with low resistance are necessary for providing highly precise separations with composite CEMs.
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    Selective membranes in water and wastewater treatment: Role of advanced materials
    (Elsevier, 2021) Zuo, Kuichang; Wang, Kunpeng; DuChanois, Ryan M.; Fang, Qiyi; Deemer, Eva M.; Huang, Xiaochuan; Xin, Ruikun; Said, Ibrahim A.; He, Ze; Feng, Yuren; Walker, W. Shane; Lou, Jun; Elimelech, Menachem; Huang, Xia; Li, Qilin; NSF Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment
    Membrane separation has enjoyed tremendous advances in relevant material and engineering sciences, making it the fastest growing technology in water treatment. Although membranes as a broad-spectrum physical barrier have great advantages over conventional treatment processes in a myriad of applications, the need for higher selectivity and specificity in membrane separation is rising as we move to target contaminants at trace concentrations and to recover valuable chemicals from wastewater with low energy consumption. In this review, we discuss the drivers, fundamental science, and potential enabling materials for high selectivity membranes, as well as their applications in different water treatment processes. Membrane materials and processes that show promise to achieve high selectivity for water, ions, and small molecules—as well as the mechanisms involved—are highlighted. We further identify practical needs, knowledge gaps, and technological barriers in both material development and process design for high selectivity membrane processes. Finally, we discuss research priorities in the context of existing and future water supply paradigms.
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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.