PVDF-g-GMA membrane was prepared by grafting glycidyl methacrylate(GMA) onto the surface of polyvinylidene fluoride(PVDF) membrane by ultrasonic assisted graft polymerization. A modified membrane with zwitterionic structure surface(PVDF-g-GMA-Thr) was prepared by grafting threonine(Thr) onto the surface of the PVDF membrane through the ring opening reaction of epoxy groups induced by amino group. The chemical composition, wettability, surface morphology and antifouling performance of PVDF membrane before and after modification were systematically studied by Attenuated total reflection Fourier infrared spectroscopy(ATR-FTIR), X-ray photoelectron spectroscopy(XPS), contact angle analyzer, scanning electron microscopy(SEM) and bovine serum albumin(BSA) filtration experiments. The results show that with the increase of PVDF-g-GMA grafted threonine reaction time, the hydrophilicity of the prepared modified membrane with zwitterionic structure surface is obviously improved, and the contact angle is reduced from 90° to 0°, showing the superhydrophilicity. At the same time, the water flux of the modified membrane is obviously improved, when the threonine induces the ring opening reaction for 12 h, the modified membrane has the highest water flux as high as 686 L/(m 2·h), it increased by 204.5%. In addition, in the filtration test of BSA, the modified membrane exhibited good anti-fouling performance and retention performance. BSA rejection ratio is increased from 42% to 84% for the modified membranes. Moreover, compared with PVDF original membrane, the water flux recovery rate of the modified membrane increased from 53% to 87% and the irreversible fouling decreased from 47% to 12%, which indicated that the membrane fouling can be effectively reduced by grafting threonine to construct zwitterionic structure surface on the PVDF membrane.
