Pesticide chemical oxidation: state-of-the-art

The various currently used chemical oxidation processes (AOPs), for pesticide elimination from wastewater are reported. Heterogeneous TiO2 photocatalysis, ozonation and photo-Fentonʹs reagent are the most intensively investigated technologies. Theoretical and practical advantages and limitations of each method are discussed. Degradation mechanism and experimental conditions employed for the optimization of each technology are reviewed. Performances such as the achieved degree of mineralization and obtained degradation rates are detailed. The various analytical approaches for studying pesticide degradation by AOPs are also discussed. Formation of by-products is unavoidable during cost effective treatments. Their detection and identification are required in order to determine which kind of chemical structures are left at the end of the process. For this purpose, the crucial role of gas and liquid mass spectrometry is emphasized. The review reveals a general lack of data on kinetics of formation and disappearance of the major by-products. The efficiency of AOPs has scarcely been investigated at industrial scales, i.e. in presence of a mixture of active ingredients together with their formulating agents and at concentration levels above 10 mg/l. The more polar by-products are largely unknown and their toxicity is usually not addressed.