Advanced Oxidation Processes for Remediation of Persistent Organic Pollutants

Abstract

Advanced oxidation processes are very efficient set of chemical reactions used for the treatment of contaminated effluents, at ambient temperature and pressure. Advanced oxidation processes (AOPs) produce reactive oxygen species (ROS) such as hydroxyl radicals (∙OH), superoxide radicals, hyperoxides (O2−), peroxides (O22−), ozone (O3), sulfides (S2−) and sulfate radicals (SO2−4). A variety of ROS are produced by either photocatalytic, physicochemical or photochemical methods. The in situ production of ROS by photochemical and non-photochemical reactions leads to secondary redox reactions to degrade organic pollutants in air and water. A variety of advanced oxidation processes are being employed for decomposition of recalcitrant pollutants in addition to cost-effective synthesis of useful organic compounds. Photocatalysis is the branch of AOPs in which a photocatalyst is irradiated with photonic energy of appropriate wavelength and used for treatment of polluted air and water, non-specifically. Basically, this technology accelerates the process of oxidation, with high rate of reaction due to the involvement of free radicals. Thus, AOPs are a very promising, eco-friendly, cost-effective and emerging technology used for effluent treatment. The main aim of this chapter is to summarize the basic mechanism of radical generation in photochemical and non-photochemical techniques of AOPs and select the most efficient advanced oxidation process. To assess the extent of degradation of organic pollutants in effluent, various technologies, their benefits and their limitations will also be summarized. The chapter summarizes the applications of AOPs, their advantages compared to other techniques, trends in pollutant remediation and future prospects.