Antifouling, adsorption and reversible flux properties of zwitterionic grafted PVDF membrane prepared via physisorbed free radical polymerization

Abstract

Zwitterionic monomer carboxybetaine methacrylate (CBMA) is well known as an excellent hydrophilic and ion adsorption material. Herein, we created a PCBMA layer on PVDF membrane surface via physisorbed free radical polymerization grafting technique (P-FFPG) to improve its hydrophilicity, antifouling and inorganic salts separation property. The key factors of monomer concentration and reaction time which influence grafted density (GD) were investigated in the present work. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) confirmed that the CBMA monomer was grafted onto the membrane successfully. The surface chemistry composition was conducted via X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) analysis clearly showed that the PCBMA layer formed on the membrane surface, and its grafted degree increased with the monomer concentration. The water static contact measurement confirmed that modified PVDF membranes obtained stable enhanced hydrophilicity and superior water adsorption ability. The static protein adsorption at different pH showed a partly pH sensitivity and an improving antifouling ability almost in the whole pH range. The ultrafiltration experiments suggested that the anti-protein fouling of the grafted membranes was significantly improved. The modified membrane possessed a stable initial sodium chloride (NaCl) rejection ratio and reversible flux behavior.