Visible-Light-Driven Photocatalytic Inactivation of Bacteria, Bacteriophages, and Their Mixtures Using ZnO-Coated HDPE Beads as Floating Photocatalyst

Semiconductor materials used as photocatalysts are considered among the most effective ways to treat biologically polluted water. Certainly, efficiency depends on the selection of photocatalyst and its substrate, as well as the possibility of its application in a broader spectrum of light. In this study, a reactive magnetron sputtering technique was applied for the immobilisation of ZnO photocatalyst on the surface of HDPE beads, which were selected as the buoyant substrates for enhanced photocatalytic performance and easier recovery from the treated water. Moreover, the study compared the effect on the inactivation of the microorganism between ZnO-coated HDPE beads without Ni and with Ni underlayer. Crystal structure, surface morphology, and chemical bonds of as-deposited ZnO films were investigated by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. Visible-light-induced photocatalytic treatment was performed on the Gram-negative and Gram-positive bacteria and bacteriophages PRD1, T4, and their mixture. Higher bacteria inactivation efficiency was obtained using the ZnO photocatalyst with Ni underlayer for the treatment of S. Typhimurium and M. Luteus mixtures. As for infectivity of bacteriophages, T4 alone and in the mixture with PRD1 were more affected by the produced photocatalyst, compared with PRD1.