Investigation of the applicability of TiO2, BiVO4, and WO3 nanomaterials for advanced photocatalytic membranes used for oil-in-water emulsion separation

Abstract

In the present study, a commercial TiO2, several BiVO4 photocatalysts, a WO3 nanomaterial, and their composites were used to prepare photocatalytic polyvinylidene fluoride (PVDF) ultrafilter membranes. Their photocatalytic activities and the effects of coatings on the filtration of oil-in-water emulsion (crude oil; coil = 100 mg L−1) were investigated. Fluxes, filtration resistances, purification efficiencies, and fouling resistance abilities—like flux decay ratios (FDRs) and flux recovery ratios (FRRs)—were compared. The solar light-induced photocatalytic decomposition of the foulants was also investigated. WO3 was used as a composite component to suppress the electron–hole recombination with the goal of achieving higher photocatalytic activity, but the presence of WO3 was not beneficial concerning the filtration properties. However, the application of TiO2, one of the investigated BiVO4 photocatalysts, and their composites was also beneficial. In the case of the neat membrane, only 87 L m−2 h−1 flux was measured, whereas with the most beneficial BiVO4 coating, 464 L m−2 h−1 flux was achieved. Pure BiVO4 coating was more beneficial in terms of filtration properties, whereas pure TiO2 coating proved to be more beneficial concerning the photocatalytic regeneration of the membrane. The TiO2(80%)/BiVO4(20%) composite was estimated to be the most beneficial combination taking into account both the aspects of photocatalytic activity and filtration properties.