Sandwich-like structure modified anion exchange membrane with enhanced monovalent selectivity and fouling resistant

Surface modification is a critical method for fabricating novel anion exchange membranes (AEMs) with high monovalent anion selectivity and desired antifouling property. In this work, we have modified a commercial AEM with sandwich-like structure, composed of upper/bottom bilayers of polydopamine (PDA) and sandwich alternating bilayers of poly (sodium 4-styrene sulfonate) (PSS)/hydroxypropyltrimethyl ammonium chloride chitosan-nano silver particles (HACC-Ag Np), aiming to enhance the monovalent selectivity and fouling resistant for electrodialysis (ED) application. Our investigations suggest that the permselectivity (P-SO42-(cl-))of the modified AEM with 4.5 bilayers of PSS can reach 5.1, significantly outperforming that of commercial standard AEM (0.98). Due to the electrostatic repulsion resulted from the negatively charged top layer in sandwich structure and hydrophilia of PDA, the time elapsed until the occurrence of fouling (transition time) of the modified AEM (125 min) is much longer than that of the original one (60 min). In addition, anchored silver nanoparticles in sandwich alternating bilayers endow the modified AEMs with effective antibacterial activities of Escherichia coli. These results are indicative of the desired fouling resistant for ED process. The facile fabrication process and superior performances of modified AEM suggest that the as-prepared sandwich-like structure modified AEM is potentially applicable in ED for separation of monovalent and multivalent anions.