Chapter 24 - ZnO-based nanoparticles for wastewater treatment: A review

Abstract

Rapid progress in industry and technological development has led to an unfortunate increase in deterioration of the health of the environment. A large number of contaminants are toxic and pose challenges in water treatment. Numerous methods are used in treatment of the pollutants, with nanotechnology being one of the promising methods. Nanomaterials have specific surface areas and properties suitable for environmental applications. ZnO is an n-type semiconductor with 3.2eV bandgap and with many active sites, and it is an effective and suitable photocatalyst that produces large numbers of hydroxyl radicals. Oxygen vacancies and oxygen and zinc interstitials are behind its photocatalytic reactions, which provide active sites for preventing electron-hole recombination. This improves the generation of hydrogen peroxide, superoxide, and hydroxyl radicals, responsible for the photocatalytic activity on the surface of ZnO. Doping increases surface defects and ZnO nanoparticles are doped with metals and transition metals that increase the photocatalytic activity, making ZnO the most efficient material in industrial wastewater treatment.