Effects of fixed charge group physicochemistry on anion exchange membrane permselectivity and ion transport
Effects of fixed charge group physicochemistry on anion exchange membrane permselectivity and ion transport
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DOI：
10.1039/d0cp00018c
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发表时间：
2020-04-14
影响因子：
3.3
通讯作者：
Geise, Geoffrey M.
中科院分区：
文献类型：
--
作者：
Ji, Yuanyuan;Luo, Hongxi;Geise, Geoffrey M.
了解聚合物化学对膜离子传输特性的影响对于设计用于水净化和能源应用的先进高选择性离子交换膜至关重要。本文研究了固定电荷基团类型对阴离子交换膜（AEM）表观选择性和离子输运性能的影响。这两种AEMs均含有类似的丙烯腈、苯乙烯和二乙烯基聚合物骨架，其固定电荷基分别为三甲基铵或1,4-二甲基咪唑。采用氯化锂、氯化钠、氯化铵、溴化钠和硝酸钠水溶液对两种AEMs的膜溶胀、表观过氧化物选择性和离子输运性能进行了表征。表观电选择性测量表明，固定电荷基团类型对表观电选择性的影响较小。然而，对膜膨胀和离子吸附的进一步分析表明，与亲水固定电荷基团相比，亲水固定电荷基团较少更有效地排除了共离子。对离子扩散特性的分析表明，离子和固定电荷基团的水化焓特性影响离子的输运，可能通过反离子凝聚、离子配对或结合机制。如果离子的水化焓与固定电荷基团的水化焓相似，则固定电荷基团与反离子之间的相互作用可能更强，并且在这种情况下观察到抑制反离子扩散。一般来说，固定电荷基的水合性质对于理解固定电荷基化学如何影响阴离子交换膜中的离子传输性质可能是重要的。
Understanding the effects of polymer chemistry on membrane ion transport properties is critical for enabling efforts to design advanced highly permselective ion exchange membranes for water purification and energy applications. Here, the effects of fixed charge group type on anion exchange membrane (AEM) apparent permselectivity and ion transport properties were investigated using two crosslinked AEMs. The two AEMs, containing a similar acrylonitrile, styrene and divinyl benzene-based polymer backbone, had either trimethyl ammonium or 1,4-dimethyl imidazolium fixed charge groups. Membrane deswelling, apparent permselectivity and ion transport properties of the two AEMs were characterized using aqueous solutions of lithium chloride, sodium chloride, ammonium chloride, sodium bromide and sodium nitrate. Apparent permselectivity measurements revealed a minor influence of the fixed charge group type on apparent permselectivity. Further analysis of membrane swelling and ion sorption, however, suggests that less hydrophilic fixed charge groups more effectively exclude co-ions compared to more hydrophilic fixed charge groups. Analysis of ion diffusion properties suggest that ion and fixed charge group enthalpy of hydration properties influence ion transport, likely through a counter-ion condensation, ion pairing or binding mechanism. Interactions between fixed charge groups and counter-ions may be stronger if the enthalpy of hydration properties of the ion and fixed charge group are similar, and suppressed counter-ion diffusion was observed in this situation. In general, the hydration properties of the fixed charge group may be important for understanding how fixed charge group chemistry influences ion transport properties in anion exchange membranes.