Fabrication of a superhydrophilic PVDF-g-PAA@FeOOH ultrafiltration membrane with visible light photo-fenton self-cleaning performance

A self-cleaning surface can effectively solve the accumulation problem of irreversible contamination of ultrafiltration membranes. In this work, a (polyvinylidene fluoride)-g-(polyacrylic acid) (PVDF-g-PAA) ultrafiltration membrane, hereafter denoted as FAS, was prepared by a one-pot method. A superhydrophilic self-cleaning ultrafiltration membrane, hereafter denoted as FASF, was then obtained based on the strong complexation of Fe3+ with the abundant carboxyl groups at the FAS surface, which then mineralized Fe3+ into β-FeOOH nanoparticles and deposited them onto the FAS surface. This deposition was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. Bovine serum albumin (BSA) cross-flow filtration experiments confirmed the high ultrafiltration performance of FAS and FASF. FASF exhibited highly efficient degradation of methylene blue (MB) solution under visible light photo-Fenton conditions. The optimum amount of acrylic acid was 6 wt% in the one-pot reaction system, and the alkaline coagulation bath enhanced the wettability of FAS. The β-FeOOH nanoparticle content of the surface-mineralized FASF tended to be saturated after 24 h. β-FeOOH can significantly enhance the hydrophilicity and wettability of FASF and further enhance the antifouling performance of BSA. After four cycles of cleaning operation under visible light photo-Fenton conditions, the flux recovery rate of BSA-contaminated FASF reached 96.2%, and the rejection rate remained stable. FASF had superhydrophilicity, high antifouling, and fast photocatalytic self-cleaning performances, indicating good application prospects in organic wastewater treatment.