Surface coating on the polyamide TFC RO membrane for chlorine resistance and antifouling performance improvement

A novel random terpolymer poly(methylacryloxyethyldimethyl benzyl ammonium chloride-r-acrylamide-r-2-hydroxyethyl methacrylate) (P(MDBAC-r-Am-r-HEMA)) was synthesized via free radical polymerization and used as the coating material on the polyamide thin film composite (TFC) reverse osmosis (RO) membrane to improve its chlorine resistance and antifouling performance. The chlorine resistance of the membranes was evaluated by cross-flow filtration of the NaClO solution. Antifouling performance was evaluated by cross-flow filtration of the protein solution and cell-culture experiments. The membrane surface was analyzed via ATR-FTIR, XPS, SEM and streaming potential measurements. The coated membrane can tolerate chlorine exposure over 16,000 ppm h, which is 7-10 times the pristine membrane. The bacteria growth can be significantly depressed on the coated membrane surface. The coated membrane can retain its flux very well under protein filtration. It is believed that the surface coating layer works as a protective and sacrificial layer, preventing the attack of chlorine on the underlying polyamide film. The PMDBAC and PAm components are essential to the antimicrobial property and the improved surface hydrophilicity is beneficial to the antifouling performance of the membrane. The coated membrane offers potential use as a novel RO membrane with improved antifouling performance and chlorine resistance.