Homogeneous trimethylamine-quaternized polysulfone-based anion exchange membranes with crosslinked structure for electrodialysis desalination

Abstract

A series of trimethylamine quaternized crosslinked anion-exchange membranes (AEMs) based on polysulfone has been prepared by using an ultraviolet cross-linking method, which avoids the uneven reaction and undesirable aggregation of the basic functional groups (trimethylamine) by heterogeneous quaternization. The ultraviolet cross-linking method makes the reaction simpler and more controllable, compared with traditional method. By crosslinking, at 40 °C, the water uptakes of as-prepared AEMs decrease from 62.6% to 36.9%, while the linear expansion ratios reducing from 26.3% to 13.4% without significantly sacrificing the surface area resistance (increased 2.32 Ω cm2 to 2.98 Ω cm2). In addition, the introduced crosslinking yields the more robust AEMs with increased tensile strength from 4.32 to 11.89 MPa and increased elongation at break in a range of 13.8–30.9%. The significantly reduced water absorption, enhanced (dimensional and mechanical) stabilities suggest crosslinkers with more acrylate groups could promote high crosslinking within AEMs. For electrodialysis (ED) application, the optimized AEM exhibits an enhanced NaCl removal ratio of 75.0%, current efficiency of 92.7% and energy consumption of 6.06 kWh Kg−1, compared with AEM without cross-linking (61.4%; 75.9%; 6.20 kWh Kg−1). This investigation demonstrates that the as-proposed strategy has certain guiding significance for the development of advanced AEMs.