Self-cleaning and antifouling polyvinylidene difluoride hollow fiber membrane enabled by visible light irradiation for water treatment

A polydopamine (PDA) layer was attached onto the surface of a polyvinylidene difluoride hollow fiber membrane via the self-polymerization of the dopamine. Amine-functionalized N-TiO2(N-TiO2-NH2) nanoparticles were covalently bound with the PDA layer via amine-catechol adduct formation. N-TiO2 anchored onto the membrane surface could be activated by visible light irradiation, thus imparting the membrane's self-cleaning activities. The coating method enhanced the contact area between photocatalytic particles and contaminants when compared to the membrane fabricated by the blending method. In comparison with ultraviolet (UV) light irradiation, the application of visible light irradiation could save energy and prevent membranes from deterioration. The membranes were characterized by scanning electron microscopy and their performances were evaluated based on the water permeability, humic acid (HA) rejection and antifouling property. Under visible light irradiation, the pure water flux of the membrane modified with (N-TiO2-NH2) (NTN) via dopamine could recover 100% of its original flux in the second day. The antifouling property of membranes modified with NTN could be further increased by UV irradiation; however, the UV light might deteriorate quickly the modified layer on the membrane surface. These results demonstrated that the methodology developed here was capable of preventing membrane fouling and cleaning the fouling surfaces. An important advantage using visible light irradiation is its relatively low energy costs and minimal deterioration of the membrane structure.