Effectiveness of AOPs processes on the removal of contaminants and their oxidation intermediates: the mepanipyrim case

Different degradation methods have been applied to assess the suitability of advanced oxidation process (AOPs) to promote the mineralization of mepanipyrim (4-Methyl-Nphenyl- 6-(1-propynyl)-2-pyrimidinamine), a fungicide belonging to the family of the anilinopyrimidine, active against gray mold (Botrytis cinerea) on grapevine, strawberry and tomato. The persistence of this active substance has been demonstrated in soil, surface and ground waters, and in water destined to human uses. Degradation processes were carried out in aqueous solutions by means of UV light, Ozone (O3), UV/O3, and heterogeneous photocatalysis using TiO2 and Pilkington Active Blue glass. The experiments were performed through a solar simulator (Suntest CPS) furnished with a xenon lamp. The identification and quantification of mepanipyrim residues and its degradation products were achieved by using liquid chromatography/DAD coupled with mass spectrometry (LC/DAD-MS). The efficiencies of the different oxidation methods were compared. Independently of the oxidation process assessed, the decomposition of mepanipyrim always followed pseudo first order kinetics, and new oxidation by-products were identified compared to literature. A large difference in the production of derivatives was observed between degradation mechanism of ozonation and heterogeneous photocatalysis using Pilkington Active Blue glas. Results showed that direct photolysis is less efficient in terms of pesticide degradation rate than the other AOPs adopted. Toxicity assays were also performed on final degradation solutions to verify if the detoxification process was really achieved