Photoinduced graft polymerization of acrylamide on polypropylene microporous membranes for the improvement of antifouling characteristics in a submerged membrane-bioreactor

Polypropylene hollow fiber microporous membranes (PPHFMMs) were surface-modified by the photoinduced graft polymerization of acrylamide (AAm). Structural and morphological changes on the membrane surface were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (FT-IR/ATR) 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 FT-IR/ATR indicated the successful graft polymerization of AAm onto the membrane surface. Water contact angle of the modified membrane decreased with the increase of the grafting degree. It showed 34.9° for the modified membrane with a grafting degree of 278.4 wt.%, nearly 94° lower than that of the nascent one. The antifouling characteristics of the PPHFMMs before and after surface modification were assessed by the filtration of activated sludge in a submerged membrane bioreactor for synthetic wastewater treatment. It demonstrated that after continuous operation for about 42 h, the flux recovery were 36.9, 63.7% and the relative flux ratio were 1.00, 1.32 for the nascent and modified PPHFMMs, respectively.