Application of anion exchange membrane and the effect of its properties on asymmetric membrane capacitive deionization.

Graphical abstract Highlights • Asymmetric MCDI with only anion-exchange membrane (AMCDI-AEM) is proposed. • AMCDI-AEM shows better performance compared with CDI. • AEM with high IEC and low resistance and water uptake favors desalination. • AEM plays a stronger role than CEM in membrane-assisted CDI application. Abstract Membrane capacitive deionization (MCDI) usually contains both anion and cation exchange membranes (AEM, CEM) to restrict the ion desorption during charging and re-adsorption during discharging in capacitive deionization (CDI). In this study, different from conventional MCDI, an asymmetric membrane capacitive deionization (AMCDI) device packing an AEM only (AMCDI-AEM) was constructed, where the AEM was lab-synthesized from poly (2, 6-dimethyl-1, 4-phenylene oxide). The effect of the AEM properties, such as ion exchange capacity, water uptake and membrane resistance on the desalination performance of AMCDI-AEM was systematically discussed. The results indicate that an AEM with high ion exchange capacity, low membrane resistance and low water uptake is beneficial for AMCDI-AEM. Furthermore, AMCDI packed with a commercial cation exchange membrane only (AMCDI-CEM) and a conventional MCDI device were also assembled to stress the importance of AEM application. Although the charge efficiency of AMCDI-AEM is lower than a full MCDI cell (54.7 vs 95.0%) due to the unprotected cathode, AMCDI-AEM device shows comparable salt adsorption capacity to MCDI (7.4 vs 7.2 mg g−1), and is much better than that of CDI (2.3 mg g−1) and AMCDI-CEM (1.5 mg g−1), suggesting that AEM plays a stronger role than CEM for membrane-assisted CDI application. By using a single AEM and commercial activated carbon electrode, this work provides an opportunity to reduce membrane cost for the industrialization of MCDI technology. [ABSTRACT FROM AUTHOR]