Photocatalytic Polysulfone Hollow Fiber Membrane with Self-Cleaning and Antifouling Property for Water Treatment

Membrane fouling is a critical issue during the membrane filtration process. Photocatalytic membranes have been developed to address the membrane fouling issue, although current approaches are mostly based on irradiation under the UV light. In this study, we report the preparation of a photocatalytic membrane with self-cleaning property under visible light irradiation. A 3-(3,4-dihydroxyphenyl)lalanine (LDOPA) layer was first attached onto the surface of polysulfone (PSF) hollow fiber membrane (HFM) via self-polymerization with an immersion time of 6 h/12 h/18 h/24 h. Then, N-TiO2-NH2 (NTN) was introduced to the LDOPA layer via chemical bonding. The NTiO2 NPs were able to degrade humic acid (HA) under visible light irradiation. Various methods were applied to characterize the photocatalyst and membrane, including thermal gravimetric analysis, scanning electron microscopy, and cyclic filtration tests of deionized water and HA solution. The normalized water flux of PSF 18LDOPA-NTN HFM was 22% higher than that of PSF HFM under visible light condition or 25% higher under the UV irradiation, measured in filtration tests lasting 6 days. In comparison with the pristine PSF HFMs under visible light irradiation, the self-cleaning performance of the modified PSF HFMs was significantly improved due to the photocatalytic property of N-TiO2 (12%, 25%, and 30% enhancements of normalized flux by 6LDOPA-NTN HFM, 18LDOPA-NTN HFM, and 24LDOPA-NTN HFM, respectively) as indicated by the experimental results of the two-day filtration.