Photocatalytic degradation of methylene blue, rhodamine B, methyl orange and Eriochrome black T dyes by modified ZnO nanocatalysts: A concise review

One of the issues receiving global attention is the prevalence of dyes in wastewater and water resources. These chemicals' persistence, toxicity, and carcinogenic potential have a significant influence on aquatics and humans, making their removal prior to discharge into the environment necessary. Semiconducting metal oxide and modified metal oxide-mediated photocatalysis has emerged as a superior wastewater treatment process to tackle the major challenges faced by traditional technologies. The multifunctional ZnO nanomaterial due to its inexpensive nature, eco-friendly, structure-dependent properties, and complete mineralization of pollutants make them more efficient semiconducting photocatalysts than other materials. It has been seen that ZnO nanomaterials can show high performance in photo-induced degradation of cationic and anionic dyes and for the treatment of industrial effluent due to its high efficiency under ultraviolet light, with a 3.37 eV the bandgap. Taking account of all these crucial aspects, this paper presents a review of recent achievements in the degradation of methylene blue, and rhodamine B as a cationic dye, and methyl orange andEriochrome black T as an anionic dye, by studying the operating parameters like reaction time, pH, initial dye concentration, and catalyst concentration, etc.