Hierarchically crosslinked anion exchange membranes for acid recovery by electrodialysis

Proton leakage in anion exchange membranes (AEMs) has seriously affected the industrial application of acid recovery by electrodialysis (ED). To achieve more efficient acid recovery performance, a hierarchical cross- linking strategy is proposed to accomplish the trade-off between anion transport and proton blocking. Trans-1,2diphenylethylene (tD) oligomer is initially introduced into the polymer backbone to form a hyperbranched cross- linking structure, allowing AEM to exhibit low swelling without affecting anion transport. In-situ crosslinking at elevated temperatures occurs through the polymer's cationic groups, which further increases the density and decreases the hydrophilicity of AEMs. The hierarchical crosslinking strategy significantly minimized the water uptake (<15 %) and swelling rate (<3.8 %) of the membrane. It attained extremely low proton leakage (H+ transport number < 10 %) while maintaining effective anion transport (area resistance approximate to 1.34 Omega cm(2)). Moreover, when compared to the commercial proton-blocking membrane (ACM), the hierarchically crosslinked AEM exhibits a shorter concentration end time and higher concentrated acid concentration. Consequently, the hierarchically crosslinked anion exchange membrane developed in this study demonstrates considerable potential for applications in ED acid recovery.