In situ formation of copper nanoparticles in carboxylated chitosan layer: Preparation and characterization of surface modified TFC membrane with protein fouling resistance and long-lasting antibacterial properties

In this study, copper nanoparticles (CuNPs) modified polyamide thin-film composite (TFC) membranes with long-lasting antibacterial properties and anti-protein-fouling properties were prepared by surface coating method. During modification, carboxylated chitosan (CCTS), a hydrophilic natural polymer, was coated onto the membrane surface, which was then treated with CuCl 2 aqueous solutions and cross-linking agent glutaraldehyde to reduce the Cu 2+ to CuNPs in situ and fix them in the cross-linked coating layer. The formation of CuNPs was confirmed by SEM, EDS and XPS analysis. Copper ion release measurement showed CuNPs modified TFC membranes (PA-CCTS-Cu) could release Cu 2+ in a slow and sustainable way due to chelating effect between CCTS and Cu 2+ . PA-CCTS-Cu had antibacterial efficiency of above 99% and could maintain it after 90   days’ immersion in water. PA-CCTS-Cu also exhibited better anti-protein-fouling performance than the pristine TFC membrane, with lower reduction of flux after fouling and higher recovery after cleaning in fouling test using bovine serum albumin as model foulant. This enhanced anti-protein-fouling performance was ascribed to the CCTS coating layer, which had enhanced hydrophilicity as assessed by contact angle measurement.