PHOTOOXIDATION OF CARBOFURAN BY A POLYCHROMATIC UV IRRADIATION WITHOUT AND WITH HYDROGEN-PEROXIDE

The photodegradation of carbofuran aqueous solutions has been conducted with direct photolysis provided by a polychromatic UV radiation source and by the combination of this UV radiation with hydrogen peroxide. In both processes, the decomposition level obtained as a function of the operating variables is reported, and the presence of tert-butyl alcohol, a scavenger of free radicals, is discussed. While the contribution of hydroxyl radicals is negligible in the direct photolysis, its reactions in the UV/H2O2 system clearly increase the carbofuran decomposition and therefore must be taken into account in the reaction rate equation for the total insecticide degradation. From the mechanisms proposed, the quantum yields for the direct photolysis and the kinetic constants for the reaction between carbofuran and the hydroxyl radicals generated in the H2O2 photolysis in the combined process are respectively evaluated.