Exploring the organic solvent resistance of anion exchange membranes based on poly(2,6-dimethyl-1,4-phenyl oxide) for electrodialysis desalination

Abstract

The development of stable ion exchange membranes applied in organic solution systems can expand the scope of practical applications. In this work, to explore the organic solvent anion exchange membranes (AEMs), a series of pyridine salt side-chains grafted poly(2,6-dimethyl-1,4-phenyl oxide)-based AEMs have been prepared for electrodialysis (ED). It is interestingly found that the as-prepared AEMs bear 3D network structure. Investigation demonstrates that the optimized AEM (BPPO-APy-6C) has an acceptable surface area resistance of 5.93 Ω·cm2 and the low swelling ratio of 2.5 % in DMSO. As for BPPO-APy-6C AEM exposed to a mixture solvent of 60 % DMSO +40 % water for 90 d, no visible appearance change is observable, indicating the improved organic solvent resistance. This has also been verified by the high desalination ratio (98.0 %) of ED with AEM after being exposed to 20 % DMSO (aq.) for 20 d. In addition, the DMSO-treated BPPO-APy-6C AEM-based ED filled with DMSO-containing 0.5 M NaCl solution shows the similar desalination ratio to that of ED with 0.5 M NaCl solution (aq.), suggesting its superior capacity of tolerating polar organic solvent. It is reasoned that the cross-linked structure and hydrophobicity of alkyl segments within AEM significantly contribute to the enhanced organic solvent resistance.