Advanced Oxidation Processes

Abstract

Advanced oxidation processes (AOPs) are effective at removing persistent organic pollutants (POPs) from water and wastewater. They are also promising and environmentally benign. AOPs mineralise pollutants by powerful oxidising agents such as hydroxyl radicals (HO^•) and sulphate radicals (SO₄^•−). This chapter presents an overview of various AOPs such as sonochemical processes, hydrocavitation, ozone-based processes, sulphate radical-based processes, and UV-based processes. The strategies to enhance the radical generation via various combinations of the above processes such as sono-Fenton, sono-photo-Fenton, sonophotolysis, sonophotocatalysis, and hydrocavitation combined with H₂O₂/O₃/persulphate; ozonolysis combined with UV/activated carbon/H₂O₂ were also explored. Along with improved pollutant degradation efficiency, processes such as sonophotocatalysis have an additional advantage as ultrasound cleans the catalyst surface providing additional surface area for the pollutants to degrade. In order to utilise the benefits of the coupling processes to the fullest, the proper study is necessary to diminish the radical scavenging effects and the associated drawbacks.