Anti-Fouling Support Layer Modification of Pressure Retarded Osmosis Membranes

The development of fouling-resistant membranes is critical to implementing pressure-retarded osmosis (PRO) for the economical production of energy from natural salinity gradients. The support layers of thin-film composite PRO membranes cause severe internal concentration polarization (ICP) and fouling, which markedly reduces permeate water flux and therefore power density. Here, mussel-inspired surface chemistry is used to coat polydopamine on the polysulfone support layer of PRO membranes for antifouling, followed by the in-situ growth of silver nanoparticles for biofouling resistance. Upon the coating of polydopamine for 1 hour, the contact angle of the polysulfone support dropped from 90° to 58°, indicating increased hydrophilicity. Protein fouling tests showed that BSA adsorption onto the polysulfone support was significantly inhibited upon polydopamine coating. SEM cross-sections of PRO membranes indicated that silver nanoparticles were present along the pore channels of the support layers. Sustained silver release from silver-coated polysulfone supports was observed over at least 30 days. In vitro functional assays demonstrated 98% inactivation of bacteria attached to the polysulfone supports after 3-h contact time. Our findings suggest that this method may provide a simple and efficient route for fabricating multifunctional membranes for antifouling and antimicrobial performance.