Surface-Charged PVDF Membrane via Assembly of Charged Hyperbranched Polyglycerol (HPG) for Suppresion of Membrane Fouling

Abstract

Surface charged polyvinylidene fluoride (PVDF) ultra/micro (UF/MF) filtration membranes were prepared by covalent assembly of various charged hyperbranched polyglycerol (HPG) to endow fouling resistance against numerous charged water contaminants. First, we prepared three types of charged HPG, i.e., neutral, positive, negative charges, by end-group modification. Next, PVDF flat membranes were treated with plasma irradiation to introduce functional groups, such as O-O, -OOH, -NH2, CONH, etc. Finally, the charged HPG was covalently bonded with the modified membrane surface using phenylene diisocyanate as a linking agent. Successful polymerization and charged modification of HPGs were examined by combined results of Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H-NMR). Attenuated total reflectance (ATR) FT-IR and X-ray photoelectron spectroscopy (XPS) spectra detected addition of the neutral HPG and charged HPGs on the surface of the charge-modified membrane. Enhancement of hydrophilic property of charge-modified membrane without severe change of their morphology was observed by analysis of water contact angle (CA) and field emission scanning electron microscope (FE-SEM). Charge characteristic of membranes were detected by ion exchange capacity (IEC) and zeta potential analysis, revealed successful charge modification. Assessment of anti-fouling property was conducted by charged proteins (bovine serum albumin and lysozyme) contained water. These results indicated that hydrophilic property and electrostatic repulsive force between charged membrane surface and identical charged contaminants decreased foulants adsorption on membrane surface. Therefore, positively or negatively charge-modified membranes exhibited best antifouling performance to co-ionized protein solution. Likewise, the neutral charge-modified membrane showed intermediate performance to both protein solutions. In addition, the charge-modified membranes occurs adsorption of counter charged proteins, which can improve charged protein separation. Thus, membrane surface modification with charged HPG makes eco-friendly membrane, that might be used as application of various wastewater and charged particle-separation.