Evaluation of self-cleaning and photocatalytic properties of modified g-CN based PVDF membranes driven by visible light.

Recently, the application of membranes faces a big challenge due to membrane fouling, to alleviate this situation, the hybridization of photocatalysis and membrane filtration has aroused significant attention. In this study, we firstly introduced melamine, cyanuric acid and urea in dimethyl sulfoxide (DMSO) as precursors to fabricated the MCU(DMSO)-CN material with excellent photocatalytic performance, and immobilized it on PVDF membranes by vacuum filtration, subsequently adding polyethylene glycol and glutaraldehyde as crosslinkers from MCU-CN/PVDF membrane. The results demonstrate that with the MCU-CN ratio increasing, the membrane flux was gradually decreased. Besides, the photocatalytic efficiencies of MCU-CN/PVDF for rhodamine B (RhB) and tetracycline hydrochloride (TC) degradation are 84.24% and 71.26% respectively, which are about 8 times higher than that of the original membrane. To evaluate antifouling performance of photocatalytic membranes, we conducted a four-stage filtration system, and the flux recovery ratio (FRR) of MCU-CN/PVDF membranes reached over 80% (optimum 91%) under visible light irradiating (λ > 420 nm) for 30 min. Meanwhile, under visible light irradiation reversible fouling (Rr) gradually became the dominant fouling factor instead of the irreversible fouling (Rir), indicating the excellent antifouling performance of MCU-CN/PVDF membranes. This novel method to modify membranes with MCU-CN gives insight to photocatalytic and self-cleaning properties of photocatalytic composite membranes, providing theoretical basis for their broad application.