Photocatalytic microfiltration membranes produced by magnetron sputtering with self-cleaning capabilities

Abstract

In the present work, asymmetric alumina flat membranes were coated with TiO2 thin films of varying thickness for wastewater treatment application. The coating was produced by magnetron sputtering, a deposition technique of high industrial relevance which could enable high volume manufacturing of photocatalyst coated membranes. The photocatalyst was used against membrane fouling, by taking advantage of the self-cleaning capabilities of TiO2 when irradiated by UV light. The morphology and pore size of the coated membranes was evaluated by scanning electron microscopy. The antifouling property of the photocatalyst was assessed against two pollutants, methylene blue (MB) in aqueous phase and soybean oily emulsion. Under ultraviolet irradiation, the coating was able to restore membrane flux by degrading the fouling formed by MB, with selectivity reaching up to 86% of MB removal for the thickest TiO2 thin film. The thickness didn’t appear to have a significant impact on the photocatalytic activity, but it was negatively correlated with pore size, which enables membrane pore size and selectivity to be tailored. In oily conditions, the photocatalyst was not able to prevent membrane fouling, which was attributed to fouling inside the pores, catalyst inactivation through the formation of an oil layer at its surface, and to a low radiant flux.