Enhancing the performance of aromatic polyamide reverse osmosis membrane by surface modification via covalent attachment of polyvinyl alcohol (PVA)

Surface modification is a promising way to improve membrane performance. In this study, a commercial aromatic polyamide thin-film composite reverse osmosis membrane was modified through sequential surface treatment with glutaraldehyde aqueous solution followed by polyvinyl alcohol (PVA) aqueous solution. ATR-FTIR spectroscopy, SEM, AFM, measurements of streaming potential and contact angle and cross-flow permeation tests were employed to investigate the influence of modification on membrane performance. It was illustrated that PVA molecules were covalently attached on the surface of the pristine membrane and both membrane surface physico-chemical and permeation properties could be tuned through changing the PVA content. The covalent attachment of PVA resulted in an improved surface hydrophilicity, a declined surface negative charge and a slightly increased surface roughness, and could enhance membrane salt rejection and water flux simultaneously. The modification was proved to be effective in improving membrane antifouling property to the foulants of bovine serum albumin, sodium dodecy sulfate and dodecyltrimethyl ammonium bromide through increasing anti-adsorption capability and in enhancing membrane chlorine stability through reducing chlorination sites and preventing the underlying polyamide backbones from chlorine attack. Furthermore, the modification could effectively enhance the membrane rejection performance and antifouling property in tertiary treatment of industrial effluent.