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A B S T R A C TThe photocatalytic degradation of the insecticide methomyl in water using TiO 2 Merck Eusolex Ò T (anatase) under Osram ultra-vitalux Ò lamp light (315-400 nm, 300 W) was studied. The effect of the operational parameters, such as initial concentration of catalyst, initial methomyl concentration, initial salt concentration (NaCl), and pH, was studied. The optimal concentration of catalyst was found to be 2.0 g/L. Using the Langmuir-Hinshelwood mechanism as a base, a pseudo-first-order kinetic model was illustrated and the adsorption equilibrium constant and the rate constant of the surface reaction were calculated (K MT = 0.079 L/mg and k C = 0.134 mg/L min, respectively). The photodegradation rate was higher in acidic than in alkaline conditions. The presence of Cl -ions significantly affected the photodegradation of the pollutant. The rate of photodecomposition of methomyl was measured using UV spectroscopy and high performance liquid chromatography, while its mineralization was followed using ion chromatography and total organic carbon analysis. In addition, several photocatalysts were used: ZnO (Merck), TiO 2 P-25 (Degussa), TiO 2 Merck (anatase), and TiO 2 Merck R-706 (rutile), and were compared with TiO 2 Merck Eusolex Ò T (anatase).

A comparative study on photocatalytic degradation of the pesticide carbofuran and its commercial product Furadan 35-ST in an aqueous suspension of ZnO, irradiated by long-wave light (315-400 nm), is presented in this study. In order to assess the effects of inert ingredients present in the commercial product Furadan 35-ST, non-competitive and competitive adsorption and kinetic studies of carbofuran degradation processes were conducted. A higher photochemical degradation rate was found for pure carbofuran in comparison to a two-component system, carbofuran and single addition of ingredients at appropriate concentrations, and the commercial product Furadan 35-ST. The overall effect of inert ingredients was evaluated from a competitive study using the model system of Furadan 35-ST. The results of a mineralization study, obtained by ion chromatography (IC) and total organic carbon (TOC) analyses, revealed the formation of acetate, oxalate, and formate ions. Photodegradation products of carbofuran, three of them detected for the first time, were identified based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) results, and their photodegradation pathways were proposed.

Catalytic wet peroxide oxidation of methomyl over Fe-ZSM-5 and AlFe-pillared montmorillonite was carried out at room temperature, in a glass batch reactor, under constant airflow and halogen lamp light. Both catalysts have shown significant activity in the degradation reaction of methomyl at a concentration of 1.0x10 -4 mol.