Comparative study of zinc oxide nanocomposites with different noble metals synthesized by biological method for photocatalytic disinfection of Escherichia coli present in hospital wastewater

Abstract

Binary zinc oxide (ZnO) nanocomposites with different noble metals silver (Ag) and ruthenium (Ru) were prepared from an aqueous leaf extract of Callistemon viminalis. The biosynthesized photocatalysts were characterized and examined for their photocatalytic disinfection against Escherichia coli isolated from hospital wastewater. The influence of the different noble metals showed a difference in physicochemical characteristics and photocatalytic efficiency between Ag朲nO and Ru朲nO. The photocatalytic degradation of methylene blue and photocatalytic disinfection were found to be in the order Ag朲nO . Ru朲nO . ZnO. The photocatalytic disinfection of Ag朲nO reached a 75% reduction in 60 min compared to 34 and 9% reductions of Ru朲nO and ZnO respectively. The kinetic reaction rate for the photocatalytic disinfection of Ag朲nO was found to be 2.8 times higher than that of Ru朲nO. The outstanding photocatalytic activity of Ag朲nO over Ru朲nO was attributed to higher crystallinity greater UVA adsorption capacity smaller particle size and the additional antimicrobial effect of Ag itself. The C. viminalis-mediated Ag朲nO nanocomposites can be a potential candidate for photocatalytic disinfection of drug-resistant E. coli in hospital wastewater. ? 2023 The Authors.