Abstract:

Based on the fact that the 18-crown-6 ether ring cavity can form a 1∶1 stable complex with K⁺, 4,4'-diamino-dibenzo-18-crown-6 (A18C6) was introduced into the ion-exchange membrane-based material and formed into a membrane, and then A18C6 molecules were cross-linked and immobilized with 1,3,5-benzenetricarbonyl chloride (TMC) to obtain a series of modified cation-exchange membranes. By changing the content of A18C6 and the reaction time of TMC to adjust the matrix structure of CEMs, the ED permselectivity to K⁺ for the modified membranes in binary systems of K⁺/Mg²⁺, K⁺/Na⁺ and K⁺/Li⁺ were systematically investigated. At a constant current density of 5.0 mA·cm^-2, the modified membrane M-A18C6-10%-T30 shows prominent permselectivity to K⁺ in K⁺/Mg²⁺ and K⁺/Li⁺ binary systems (P_{\mathrm{M}{\mathrm{g}}^{\mathrm{2}+}}^{{\mathrm{K}}^{+}}=\mathrm{6.96},P_{\mathrm{L}{\mathrm{i}}^{+}}^{{\mathrm{K}}^{+}}=\mathrm{3.73}), which is superior to commercial monovalent selective cation exchange membrane (MSCEM) CIMS (P_{\mathrm{M}{\mathrm{g}}^{\mathrm{2}+}}^{{\mathrm{K}}^{+}}=\mathrm{5.36}). The introduction of A18C6 improves the compactness of membrane matrix (pore-size sieving effect) and further provides new ion transport channels for K⁺ (ion-dipole interaction).

Key words: membranes, electrodialysis, ion exchange, 4,4'-diamino-dibenzo-18-crown-6, selectivity

摘要：

基于18-冠-6醚环腔体可与K⁺形成1∶1型稳定的络合物，通过掺杂的方式将4，4'-二氨基-二苯并-18-冠-6（A18C6）引入离子交换膜基材料中并成膜，然后利用1，3，5-苯三甲酰氯（TMC）对A18C6分子进行交联固定，制得一系列改性阳离子交换膜。通过改变A18C6的含量和TMC的反应时间来调控阳离子交换膜的基体结构，系统考察了改性膜在K⁺/Mg²⁺、K⁺/Na⁺ 和K⁺/Li⁺的二元体系中对K⁺的电渗析选择性。研究结果表明，在电流密度为5.0 mA·cm^-2的条件下，最优膜M-A18C6-10%-T30在K⁺/Mg²⁺和K⁺/Li⁺体系中对K⁺的选择性（P_{\mathrm{M}{\mathrm{g}}^{\mathrm{2}+}}^{{\mathrm{K}}^{+}}=\mathrm{6.96}，P_{\mathrm{L}{\mathrm{i}}^{+}}^{{\mathrm{K}}^{+}}=\mathrm{3.73}）高于商业的单价选择性阳离子交换膜CIMS（P_{\mathrm{M}{\mathrm{g}}^{\mathrm{2}+}}^{{\mathrm{K}}^{+}}=\mathrm{5.36}）。A18C6的掺杂引入不仅提高了膜基体的致密性（孔径筛分效应），也为K⁺在膜基体中的传输提供了新的离子传输通道（离子-偶极作用）。

关键词: 膜, 电渗析, 离子交换, 4, 4'-二氨基-二苯并-18-冠-6, 选择性