Surface Modification of Polyamide Nanofiltration Membrane by Grafting Zwitterionic Polymers to Improve the Antifouling Property

A simple two-step surface modification method of polyamide nanofiltration membrane, involving the activation of amide groups by formaldehyde and the subsequent cerium [Ce (IV)]-induced graft polymerization of zwitterionic 3-(methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide) (MPDSAH) monomers, was employed to improve membrane antifouling property. The membranes before and after modification were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy, and atomic force microscopy. The changes in both surface chemical composition and morphology of membranes confirmed the successful graft polymerizations of MPDSAH onto polyamide nanofiltration membrane. The static water contact angle measurements showed that surface hydrophilicity of the modified membranes was significantly enhanced. As the MPDSAH concentration increased, the water flux of grafted membrane decreased gradually, while salt rejection increased slightly. The fouling experiments with bovine serum albumin solution demonstrated that modified membranes exhibited better resistance to protein fouling. (C) 2014 Wiley Periodicals, Inc.