Preparation of hydrophilic polyvinylidene fluoride/polyvinyl alcohol ultrafiltration membrane via polymer/non-solvent co-induced phase separation method towards enhance anti-fouling performance

Membrane separation is a common water treatment technology, but the problem of membrane fouling should not be ignored. Hydrophilic modification is an effective method to reduce membrane fouling. Therefore, PVA/non-solvent co-induced phase separation method was proposed to achieve PVDF ultrafiltration membrane hydrophilic modification and structural control with high concentration polymer coagulation bath. PVA was uniformly distributed on the surface and inside of the hydrophilic modified membrane, which was stable and not easy to leach during filtration. With increasing PVA content in coagulant, the phase separation process changed from instantaneous to delayed, and the membrane surface changed from dense to spherulitic particle accumulation structure, while the connectivity of sponge pores was enhanced until it was completely transformed into a uniform spherical particle structure. The irreversible pollution rates of the modified membrane were 3.28% and 3.48%, respectively, which were significantly lower than those of the unmodified PVDF membranes (25% and 15.26%, respectively) when filtering simulate municipal wastewater with protein and humic acid. The flux recovery rate of the modified PVDF membrane was basically maintained above 90%. This study was a one-step method for membrane structure optimization and hydrophilic modification and contributed a theoretical basis for the role of high concentration polymer coagulant in the membrane forming process.