Tuning charge density in tethered electrolyte active-layer membranes for enhanced ion-ion selectivity
Tuning charge density in tethered electrolyte active-layer membranes for enhanced ion-ion selectivity
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DOI：
10.1016/j.memsci.2022.121214
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发表时间：
2022-11
影响因子：
9.5
通讯作者：
C. Porter;Li Wang;Mingjiang Zhong;M. Elimelech
中科院分区：
文献类型：
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作者：
C. Porter;Li Wang;Mingjiang Zhong;M. Elimelech
为了实现零液体排放和循环经济，已经加强了开发除脱盐之外的用于水分离的膜的努力。非常规废水和盐水的处理以及有价值物质的回收需要溶质和离子的分离。最近，栓系电解质活性层膜（TEAM）与密集的可电离刷聚合物接枝纤维素超滤支持被引入作为一个强大的，高度可控的膜平台，这些水分离。在这项研究中，我们研究了单嵌段TEAM的交联，以增加有效电荷密度和活性层对孔的覆盖，并可能利用基于尺寸的排阻机制。我们还确定，如果交联的多嵌段TEAM包括嵌段共聚物的负电荷和正电荷可以更好地对齐块，从而提高离子排斥。具有相对短的交联剂的单嵌段TEAM被证明在稀溶液中具有最高的二价共离子截留率，为1085 - 95%。NaCl被拒绝了55%和80%的交联负电荷和正电荷的TEAM，分别。阴离子单价选择性，Cl−/SO 42 −，在负TEAM中高达1.25，而在正TEAM中达到的最大Na+/Ca 2+比为1.95。这项工作加强了反刷活性层膜和TEAM作为重要工具的价值，以了解通过膜的基本传输和更好地控制合成的目标选择性。
Efforts toward developing membranes for aqueous separations beyond desalination have intensified, in attempts to achieve zero liquid discharge and a circular economy. Treatment of unconventional wastewaters and brines as well as recovery of valuable species require separation of solutes and ions. Recently, tethered electrolyte active-layer membranes (TEAMs) with dense ionizable brush polymers grafted from cellulose ultrafiltration supports were introduced as a robust, highly controllable membrane platform for these aqueous separations. In this study, we investigate crosslinking of single-block TEAMs to increase the effective charge density and coverage of pores by the active layer, and to possibly tap into size-based exclusion mechanisms. We also determine if crosslinking multiblock TEAMs comprising block copolymers of both negative and positive charge can better align blocks, thereby improving ion rejection. Single-block TEAMs with relatively short crosslinkers proved to have the highest divalent co-ion rejection in dilute solutions, at ∼85–95%. NaCl was rejected ∼55 and 80% by crosslinked negatively- and positively-charged TEAMs, respectively. Anion monovalent selectivity, Cl−/SO42−, was as high as ∼25 for negative TEAMs, while the maximum Na+/Ca2+ratio achieved by positive TEAMs was ∼9.5. This work reinforces the value of ultrathin brush active-layer membranes and TEAMs as important tools to understand fundamental transport through membranes and better control synthesis for targeted selectivity.