Photocatalytic anti-biofouling performance of nanoporous ceramic membranes treated by atomic layer deposited ZnO

Biofouling caused by microorganisms is a critical problem in membrane treatment systems. In this study, we immobilized a highly photocatalytic active thin ZnO film on the surface of a nanoporous ceramic membrane using atomic layer deposition (ALD). Through a series of membrane characterizations, we confirmed that ALD ZnO is successfully deposited uniformly along the inner surface of the nanopores in the active layer of the membrane as desired. Additionally, the ALD ZnO-treated ceramic membrane exhibited excellent photocatalytic activity with a ZnO thickness of 36.5 nm under 1 mW/cm² of UV-A light irradiation. Compared to the bare ceramic membrane, the ALD ZnO-treated membrane with UV-A irradiation showed higher anti-biofouling efficacy. We propose that reactive oxygen species generated from ZnO may impede microbial initial adhesion, thus inhibiting biofilm formation. However, with high irradiation intensity of UV-A, water flux decreased owing to membrane pore constriction, although no significant biofilm formation was observed. Nevertheless, the proposed ALD ZnO treatment on the nanoporous ceramic membrane is expected to provide a promising novel approach for effective prevention of biofouling in membrane-based processes.