Surface layer modification of AEMs by infiltration and photo‐cross‐linking to induce monovalent selectivity

Surface modification of anion exchange membranes (AEMs) by attaching a negatively charged layer is the main method for preparing monovalent anion selective membranes. However, tremendous increase of membrane resistance and poor long‐term stability of the modified membranes face great challenges. In this work, a photosensitive molecule (4,4‐diazostilbene‐2,2‐disulfonic acid disodium salt [DAS]) was infiltrated into the membrane surface and immobilized in the structure by cross‐linking under UV irradiation. This method introduced negative charge to the surface layer of the AEMs without increasing membrane thickness, leading to high performance membrane with high monovalent anion selectivity. The optimized membrane (D‐5) shows the highest perm‐selectivity of 11.21, which is superior to the commercial selective membrane Selemion^® ASV and previously reported monovalent anion selective AEMs. Furthermore, the newly developed membrane exhibits excellent long‐term stability, which can maintain constant selectivity during the 80 h ED experiment. © 2017 American Institute of Chemical Engineers AIChE J, 64: 993–1000, 2018