Low fouling and improved chlorine resistant thin film composite reverse osmosis membranes by cerium(IV)/polyvinyl alcohol mediated surface modification

Abstract

We report the Ce(IV)/polyvinyl alcohol (PVA) redox system mediated rapid surface modification of polyamide thin film composite (TFC) reverse osmosis (RO) membrane for the improvement of both antifouling and chlorine resistant properties. Copolymerization of 3-sulphopropyl methacrylate (SPMA) and methylene-bis-acrylamide (MBA) in the presence of Ce(IV)/PVA on premade TFC membrane provided surface modified membranes. The successful surface modification of TFC membranes was evident from attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), contact angle (θ), scanning electron microscope (SEM) and atomic force microscope (AFM). Based on IR, SEM, AFM and θ, it is concluded that a soft hydrophilic polymer layer of a complex mixture of PVA-g-poly(SPMA-co-MBA), polyamide-g-poly(SPMA) and polyamide-g-poly(SPMA-co-MBA)-g-PVA like structures was generated on membrane surface. The modified membranes exhibited much enhanced antifouling property during desalination of water in the presence of scale forming salt and protein compared to that of the unmodified membrane. The chlorine stability test at accelerated conditions clearly indicated enhanced chlorine resistance by the modified membranes compared to unmodified membrane. The enhanced antifouling and chlorine stability of the modified membranes might be the result of the formation of a complex polymeric protective layer on top of polyamide barrier layer.