C3N4-BiOBr/PVC photocatalytic submerged membrane for oil-in-water emulsion separation with visible light-driven self-cleaning performance

Membrane separation has been widely used for oil-in-water separation, but the fouling of oil droplets on the membrane surface is still a challenge. Coating a photocatalyst layer on the membrane surface is an effective method for the regulation of hydrophobicity, degradation of stuck oil, and boosting the self-cleaning properties of the membranes. Thus, in this work, a heterostructure photocatalyst of carbon nitride-bismuth oxybromide (C3N4-BiOBr) with different proportions was coated on a polyvinyl chloride (PVC) layer and the performance of the resultant membrane was studied in the separation of oil-in-water emulsion under visible light. The experimental results exhibited that the membrane with C3N4 to BiOBr ratio of 40:10 coating had the lowest water contact angle of 42°, the maximum light harvesting, the lowest surface roughness, and the low recombination rate of charge carriers. The correlations drawn between surface morphology and fouling behavior of this membrane led to the maximum flux of 65 L·m−2·h−1, 99% separation efficiency, 100% Total Organic Carbon (TOC) removal, and excellent self-cleaning properties (flux recovery ratio of 93.8%). Therefore, this study provides a novel design strategy for multifunctional membranes that achieve effective treatment of oil-in-water emulsion wastewater.