Improvement of the antifouling characteristics for polypropylene microporous membranes by the sequential photoinduced graft polymerization of acrylic acid

Surface modification of polypropylene hollow fiber microporous membranes (PPHFMMs) was performed by a sequential photoinduced graft polymerization of acrylic acid (AA) from water solution. Structural and morphological changes on the membrane surface were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR) and field emission scanning electron microscopy (FE-SEM). Water contact angles of the membrane surfaces were also measured by the sessile drop method. Results of ATR/FT-IR indicated the successful graft polymerization of AA onto the membrane surface. Water contact angle of the modified membrane decreased with the increase of the grafting degree (GD). It showed 68° for the grafted membrane with a GD of 45.8 wt.%, nearly 61° lower than that of the nascent one. The pure water fluxes of the studied membranes depending on GD and pH value were studied. It was found that the pure water flux increased with the increase of GD and the decrease of pH value. The antifouling characteristics for the PPHFMMs before and after surface modification were assessed by the filtration of activated sludge in a submerged membrane bioreactor for synthetic wastewater treatment. Results demonstrated that after continuous operation for about 85 h, the flux recovery was 13.7% and 25.4% while the flux ratio was 1.00 and 2.52 for the nascent and grafted PPHFMMs, respectively.