Phototransformation of pesticide by UV, H2O2/UV and the combination of moroccan natural phosphate and UV radiation in dilute aqueous solution

The degradation of oxamyl in purified water has been studied in the process of photolysis under polychromatic radiation (lambda>285 nm), process of photolysis in homogeneous media using a combination of ultraviolet light (lambda = 253.7 nm) with hydrogen peroxide H2O2/UV and process of photolysis in heterogeneous media using a quasi-monochromatic irradiation (lambda = 365 nm) in aqueous suspensions containing natural phosphate (NP). Upon polychromatic excitation, apparent first-order kinetic constants have been determined. For oxidation by H2O2/UV the rate constant of the reaction of hydroxyl radicals HO center dot with oxamyl, determined by kinetic experiments, was evaluated to be equal to 2,45.10(9) L.mol(-1)s(-1). The same primary photoproducts: the isomer (E) and nitrile derivative (N,N-dimethyl-2-nitrilo-acetamide) have been formed in the process of photolysis under polychromatic radiation and the process H2O2/UV. In the case of the phototransfomation of oxamyl in the presence of NP, a single photoproduct was identified by LC/MS analysis as the derivative of oxime.