Cysteamine- and graphene oxide-mediated copper nanoparticle decoration on reverse osmosis membrane for enhanced anti-microbial performance.

In this work, copper nanoparticles (CuNPs) were decorated onto the polyamide RO membranes via in-situ reduction for biofouling mitigation. To increase CuNPs loading and improve anti-microbial properties of the membrane, cysteamine (Cys) and graphene oxide (GO), which contain different functional groups with high metal affinity, were applied as bridging agents between CuNPs and membrane surface via covalent bonding. The functionalization of Cys and GO linkers on membrane was confirmed by XPS and SEM analysis. By applying the linkers, the loading quantity of copper, in particular on Cys-modified membrane, was significantly improved and the particle size of CuNPs appeared smaller and had more uniform distribution. The GO medium increased the hydrophilicity of CuNP-decorated membranes, leading to an increase in water permeation with minor impact on membrane's salt rejection. Bacterial inactivation of the Cys-Cu- and GO-Cu-functionalized membranes was over 25% higher than that of the bare CuNP-coated surface, indicating enhanced bacterial inactivation benefiting from the application of linkers. After a CuNPs' release test, the membranes modified with Cys and GO retained larger quantities of CuNPs and showed better antimicrobial performance than that of bare CuNP-modified membranes. The successful regeneration of CuNPs after their depletion demonstrated the modified membranes' potential for long-term application.