Synthesis and Repetitive Application of Nanocrystalline ZnO Based Floating Photocatalyst for the Detoxification of Water from Bacteria and Viruses Mixtures

Abstract

Usually, the most efficient photocatalyst materials are synthesized as fine nanocrystalline powders and this rises significant handling and repetitive application issues. More recently, researchers started to immobilize photocatalyst (nano)materials on relatively large low density supports creating floating photocatalyst particles. Such approach allows to effectively retrieve and re-apply the used photocatalyst material. In current study we used reactive magnetron sputtering technique and deposited unconventional orange colour nanocrystalline ZnO based photocatalyst on floating high-density polyethylene (HDPE) grains. The structure of the synthesized photocatalyst was characterized by XRD, SEM, and XPS techniques. The repetitive measurements of Rhodamine B (RhB) dye bleaching by the ZnO based photocatalyst film under visible light irradiation showed high stability over ten cycles. Visible light induced photocatalytic efficiency of the floating photocatalyst grains (FPG) was also estimated by the repetitive treatment of water samples containing Salmonella typhimurium (strain SL1344) and Micrococcus luteus bacteria, as well as water samples containing PRD1 and T4 bacteriophages. These tests indicated complex interaction between the bacteria, viruses, photocatalyst and its HDPE support. For example, they revealed that FPGs lose most of its photocatalytic efficiency in just 3 cycles. To stabilize the ZnO based FPGs and enhance its photocatalytic efficiency under the visible light irradiation, before the depositing of ZnO films we pre-covered HDPE grains by Ni underlayer. The addition of Ni resulted in mixed results – Ni underlayer reduced the efficiency of S. typhimurium disinfection during the first cycle but increased the efficiency and detoxication stability over consecutive tests using the same set of FPGs.