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Membrane fouling is still the main obstacle for the wider application of membrane processes. In this study, different amounts of silver modified graphitic carbon nitride (Ag/g-C3N4) were firstly introduced into polyethersulfone (PES) membranes by blending via a phase-inversion method. The impacts of Ag/g-C3N4 addition on the membrane morphology, filtration and photocatalysis antifouling properties of Ag/g-C3N4/PES nanocomposite membranes were systematically studied. The results illustrated that the addition of Ag/g-C3N4 could make the finger-like voids in Ag/g-C3N4 nanocomposite membrane longer and wider, increasing the hydrophilicity and filtration property of the nanocomposite membrane. Also the addition of Ag/g-C3N4 nanosheets could endow the nanocomposite membranes with excellent antibacterial, photocatalytic dye degradation and antifouling properties under visible light irradiation.

An improved photocatalytic microfiltration membrane was successfully prepared by the impregnation method with nitrogen-doped TiO2/graphene oxide (GO) (NTG). By utilizing the unique role of N and GO, the photocatalytic activity of the membrane in UV and sunlight was improved. Compared with the Polyvinylidene Fluoride (PVDF) microfiltration membrane which was modified by TiO2, N-TiO2 (NT) and TiO2-GO (TG), the NTG/PVDF membrane exhibited high photocatalytic efficiency and significantly improved photodegradation power to the methylene blue (MB) solution under ultraviolet light and sunlight, with the photocatalytic efficiency reaching 86.5% and 80.6%, respectively. Scanning electron microscopy (SEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the morphology, crystal structure and chemical bonds of the membrane surface. The hydrophilicity of the modified PVDF microfiltration membrane was significantly improved, the flux of the pure water membrane reached 1672 Lm&minus, 2h&minus, 1, the flux of the MB solution was also significantly improved due to photodegradation. Therefore, the nitrogen-doped titanium dioxide graphene oxide PVDF microfiltration membrane (NTG/PVDF membrane) has great development prospects in sustainable water treatment.