Improved protein fouling resistance of PVDF membrane grafted with the polyampholyte layers

This work aims to improve the antifouling property of poly(vinylidene fluoride) (PVDF) membrane. The pristine PVDF membrane was treated with alkali solution, and then the [2-(methacryloyloxy)ethyl] trimethylammonium chloride (DMC) and 2-acrylamide-2-methyl propane sulfonic acid (AMPS) monomers were grafted to yield a polyampholyte membrane surface via radical grafting copolymerization. The structural evolution of the membrane was characterized by Fourier transform infrared spectra attenuated total reflection spectra (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM). The surface hydrophilicity of membranes was determined by pure water contact angle. The fouling resistance of the membranes was evaluated via protein adsorption and cycle filtration. With the increase of alkali-treatment periods from 0 to 20 min, the grafting degree (GD) of polyampholyte layer increases from 0 to 225.8 μg/cm², and the membrane surface pores are gradually covered with grafting layers. The hydrophilicity of PVDF membrane was significantly enhanced by the covalent immobilization of polyampholyte layer, resulting in inhibition of protein adsorption. The pure water flux recovery (FRR) of the polyampholyte membrane is much higher than that of the pristine PVDF membrane. Irreversible membrane fouling is gradually transmitted into reversible membrane fouling in the filtration process. The polyampholyte membrane exhibits a better protein fouling resistance than pristine PVDF membrane.