Soft template promoted microphase separation in anion exchange membrane of electrodialysis

This work reports a novel, effective, soft template strategy that can fabricate good-performance anion exchange membranes (AEMs) for electrodialysis application. Specifically, 1,2-ethanedisulfonic acid (EDA) is used as a small-molecule, soft template to promote microphase separation in multi-cation functionalized poly (2,6-dimethyl-1,4-phenylene oxide) membranes through electrostatic interaction between quaternary ammonium groups and sulfonic acid groups. The enhanced microphase separation has been confirmed by transmission electron microscopy (TEM) and small angle X-ray scattering studies. The prepared TPPO-2S-x membranes (where x represents the mass percent of EDA) were tested in the electrodialysis device for desalinating 0.1 M NaCl solution. Among them, the TPPO-2S-1 membrane gave the highest ED current efficiency (92.90 %), the lowest energy consumption (4.08 kWh kg−1), and the largest Cl− transport number (0.98); these performance results are better compared with those of the TPPO-2S-0 membrane (89.29 %, 4.39 kWh kg−1, and 0.98), which is not processed by soft template strategy. Although the TPPO-2S-4 and TPPO-2S-7 membrane show more obvious microphase separation than TPPO-2S-1, the current efficiencies of their ED devices are lower and the energy consumptions are higher due to their undesirable surface area resistance and chloride ion transport number. The investigation demonstrates that the soft template strategy is effective to improve membrane performance in ED devices.