Synthesis method, antibacterial and photocatalytic activity of ZnO nanoparticles for azo dyes in wastewater treatment: A review

Abstract

These days, with the increasing problem of water contamination by effluents released from rising expansion of textile, leather, paper and ink industries and problems related to disease causing pathogenic microorganisms, the need for a substance with antimicrobial and photocatalytic activity is very high. Interesting properties of ZnO nanoparticles (NPs) such as non-toxicity, low cost, biocompatibility, chemical stability, thermal and photostability, high UV absorption ability have made it a promising photocatalyst for removing hazardous contaminants especially azo dyes in wastewater. However, the toxic nature of ZnO NPs for microbes, in particular, bacteria coupled with the properties mentioned have made it a preferable antimicrobial agent in medicine and food packaging for inhibiting microbial growth. In this review, the physical and chemical properties, synthesis approaches, antibacterial activity, and photocatalytic activity of ZnO NPs are discussed. Since many properties of ZnO NPs, and hence its application, depend on the synthesis method employed, focus is given on the biosynthesis of ZnO NPs from plant extracts. Moreover, factors affecting photocatalytic activity in the photocatalytic degradation of azo dyes in wastewater treatment as well as antibacterial activity of ZnO NPs are highlighted based on recent reports in the literature.