Browsing by Author "Elimelech, Menachem"

Now showing 1 - 7 of 7
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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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    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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    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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    Selective removal of divalent cations by polyelectrolyte multilayer nanofiltration membrane: Role of polyelectrolyte charge, ion size, and ionic strength
    (Elsevier, 2018) Cheng, Wei; Liu, Caihong; Tong, Tiezheng; Epsztein, Razi; Sun, Meng; Verduzco, Rafael; Ma, Jun; Elimelech, Menachem; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment
    We fabricatedﾠpolyelectrolyteﾠmultilayerﾠ(PEM)ﾠnanofiltrationﾠ(NF) membranes using a layer-by-layer (LbL) method for effective removal of scale-forming divalent cations (Mg2+, Ca2+, Sr2+, and Ba2+) from feedwaters with different salinities. Twoﾠpolymersﾠwith opposite charges, polycation (poly(diallyldimethylammonium chloride), PDADMAC) and polyanion (poly(sodium 4-styrenesulfonate), PSS), were sequentially deposited on a commercialﾠpolyamideﾠNF membrane to form a PEM. Compared to pristine and PSS-terminated membranes, PDADMAC-terminated membranes demonstrated much higher rejection of divalent cations and selectivity forﾠsodiumﾠtransport over divalent cations (Na+/X2+) due to a combination of both Donnan- and size-exclusion effects. A PDADMAC-terminated membrane with 5.5 bilayers exhibited 97% rejection of Mg2+ﾠwith selectivity (Na+/Mg2+) greater than 30. We attribute the order of cation rejection (Mg2+ﾠ> Ca2+ﾠ> Sr2+ﾠ> Ba2+) to the ionic size, which governs both the hydration radius and hydration energy of the cations. The ionic strength (salinity) of the feed solution had a significant influence on both water flux and cation rejection of PEM membranes. In feed solutions with high ionic strength, abundant NaCl salt screened the charge of the polyelectrolytes and led to swelling of the multilayers, resulting in decreased selectivity (Na+/X2+) and increased water permeability. The fabricated PEM membranes can be potentially applied to the pretreatment of mild-salinity brackish waters to reduce membrane scaling in the mainﾠdesalinationﾠstage.
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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.
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    Ultrahigh resistance of hexagonal boron nitride to mineral scale formation
    (Springer Nature, 2022) Zuo, Kuichang; Zhang, Xiang; Huang, Xiaochuan; Oliveira, Eliezer F.; Guo, Hua; Zhai, Tianshu; Wang, Weipeng; Alvarez, Pedro J.J.; Elimelech, Menachem; Ajayan, Pulickel M.; Lou, Jun; Li, Qilin; NSF Nanosystems Engineering Research Center Nanotechnology-Enabled Water Treatment
    Formation of mineral scale on a material surface has profound impact on a wide range of natural processes as well as industrial applications. However, how specific material surface characteristics affect the mineral-surface interactions and subsequent mineral scale formation is not well understood. Here we report the superior resistance of hexagonal boron nitride (hBN) to mineral scale formation compared to not only common metal and polymer surfaces but also the highly scaling-resistant graphene, making hBN possibly the most scaling resistant material reported to date. Experimental and simulation results reveal that this ultrahigh scaling-resistance is attributed to the combination of hBN’s atomically-smooth surface, in-plane atomic energy corrugation due to the polar boron-nitrogen bond, and the close match between its interatomic spacing and the size of water molecules. The latter two properties lead to strong polar interactions with water and hence the formation of a dense hydration layer, which strongly hinders the approach of mineral ions and crystals, decreasing both surface heterogeneous nucleation and crystal attachment.