Influence of the ions distribution of anion-exchange membranes on electrodialysis

Abstract

Anion exchange membranes (AEMs) are the cores of electrodialysis (ED) desalination devices, which have attracted wide attention in recent years. However, the influence of the ions distribution of AEMs on ED performances has not been well explored, which is strongly instructive to design the ED AEMs. Here we synthesized two kinds of side-chain-ionic AEMs QPAES-a and QPAES-b, and main-chain-ionic AEM QPAES-c. To uncover the relationship between the AEMs structures and properties, these AEMs were characterized with 1H NMR and FTIR, and evaluated in terms of ion exchange capacity, water uptake, swelling ratio, λ, conductivity and transport number. Especially, we used NaCl aqueous solution to simulate seawater to investigate the ED performances of the synthesized AEMs by 180 min of ED processes. To distinguish our AEMs, the ED performance of commercial TWEDAI was similarly tested for comparison. The results confirmed that the ED performance with a lowest final conductivity of 430 μS·cm−1 of the main-chain-ionic QPAES-c is much better than that of TWEDAI and the side-chain-ionic AEMs. The ED performance stability tests convinced that QPAES-c had ED lifetime comparable to that of TWEDAI. These results show that the main-chain-ionic AEMs have their potential as ED AEMs.