Investigation of the antifouling behavior based on polyamide reverse osmosis membrane with different surface charges regulated by polyvinyl alcohol

Reverse osmosis (RO) membranes have been widely used in desalination and wastewater treatment. However, membrane fouling is still a tough issue for their long-term utilization. Here, polyvinyl alcohol (PVA) was introduced into the aqueous phase to optimize the surface charge characteristics of membrane by regulating the diffusion rate of aqueous monomer. As a result, the water flux increased to 22.61 L/m2h, nearly 30 % improvement over the original membrane, while maintaining a 97.6 % NaCl rejection rate. Additionally, fouling behavior of RO membranes was systematically investigated using three types of organic dye under various conditions including physical adsorption by molecular simulation, adsorption by electrostatic attraction and cross-flow flushing. Unexpectedly, dye molecule with more negative charges would more easily be adsorbed onto the more negative membrane in static adsorption process due on the layer-by-layer electrostatic attraction between positive and negative charges in ionic aqueous solution, however, it could more easily to be removed. The PVA-2 membrane, with higher negative charge, demonstrated an increased flux recovery rate for negatively charged dyes, which plays a crucial role in reducing irreversible fouling. This study systematically investigated the membrane fouling process from various dimensions, revealing the critical role of surface charge on antifouling performance of RO membranes.