Sonophotocatalytic Degradation of Pollutants by ZnO-Based Catalysts: A Review

Sonophotocatalyticprocess (SPC) is the simultaneous use of ultraviolet radiation (UV), ultrasonic radiation (US), and semiconductor materials as photocatalysts and sonocatalysts for the generation of reactive oxygen species (ROS). These free radicals oxidize several pollutant molecules in various industrial wastewaters. The objective of this review was to compare the papers published on the sonophotocatalytic degradation of different pollutants in the presence of zinc oxide-based particles. The elimination rate of contaminants in this process was compared with individual methods such as sonocatalysis and photocatalysis. The experimental conditions, including the catalyst dosage, the pollutant concentration, the radiation power, the applied frequency, the initial pH, and the reaction time were further investigated. ZnO nanoparticles are well-known as semiconductor materials with good sonophotocatalytic activity. In general, sonophotocatalysis is emerging as one of the most efficient treatment techniques for degrading the recalcitrant pollutants in the aqueous medium. It is expected that these technologies result in more progressive research with the most degradation efficiency.