Acid enrichment via electrodialyser fabricated with poly(vinyl chloride)-based anion exchange membrane: Effect of hydrophobicity of aliphatic side-chains tethered on imidazolium groups

• A series of AEMs based on imidazolium functionalized poly(vinyl chloride) has been prepared. • Micro-structure of PVC AEMs was tuned by the lengths of alkyl side-chains on imidazolium. • Acid blocking performance of as-prepared AEM outperforms the commercial Neosepta ACM. • The maximum concentration of H + enriched by the optimized AEM is achieved to 1.81 M. Electrodialysis (ED) technology equipped with proton blocking anion exchange membranes (AEMs) has great potential applications in recovering acidic wastewater. To develop high performance proton-blocking AEMs, in this work, a series of imidazolium functionalized poly(vinyl chloride) (PVC) AEMs are designed. In particular, the length of alkyl side chains tethered on the imidazole compound is optimized to adjust the micro-structure of AEM. Our research demonstrates that the density of 1-butylimidazole functionalized PVC AEM matrix is enhanced, which has been proved by water uptake and thermogravimetric analysis. Hence, the acid blocking performance of optimized AEM (PVC-Im-4C) is strengthened. The maximum concentration of H + in concentrate chamber of electrodialyser enriched by the PVC-Im-4C AEM is 1.81 M through the 24 h ED process at a current density of 20 mA·cm −2 (the initial concentration of hydrogen ions: 1.0 M). The result suggests that the optimized PVC-Im-4C AEM with long alkyl side chain on imidazole shows the excellent capacity in acid enrichment. This work should provide guidance for the follow-up design of the advanced proton blocking AEMs.