Tuning the length of aliphatic chain segments in aromatic poly(arylene ether sulfone) to tailor the micro-structure of anion-exchange membrane for improved proton blocking performance

Abstract

Proton blocking anion exchange membrane (AEMs) can be used to treat various of acidic wastewater (i.e., enrich the recovered acid from acidic wastewater). In this work, four AEMs based on aliphatic chain segment imbedding poly(arylene ether sulfone)s bearing salt-terminated side-chains have been prepared for acid enrichment by electrodialysis (ED). In particular, the length of flexible aliphatic chain segments (methylenes of –(CH2)3–), –(CH2)6–, –(CH2)9–, and –(CH2)12–) in aromatic poly(arylene ether sulfone) was tuned to tailor the micro-structure. Our investigation demonstrates that the AEM with aliphatic chain segments of –(CH2)12– shows the strongest surface hydrophobicity (water contact angle: 107°) and has the smallest ion clusters (0.75 nm, relative to the other three AEMs with 0.78 nm, 0.80 nm, and 0.81 nm). In ED process, at the current densities of 10 mA cm−2, the maximum concentration of H+ enriched by the AEM is 2.06 M (initial concentration: 1.0 M). The investigations demonstrate that the optimized AEM with stronger hydrophobicity and smaller ion clusters shows the superior capacity of acid concentration relative to commercial AEM (AMX, Astom Japan). This work should be certain guiding significance for designing advanced proton blocking AEMs.