Photo-oxidative degradation of insecticide dichlorovos by a combined semiconductors and organic sensitizers in aqueous media

Organophosphorus insecticide dichlorovos (DDVP) can be photodegraded into chloride ion, water, carbon dioxide and other compounds in an aqueous solution containing semiconductor powder suspensions, using ultraviolet light. Thermostatic photolytic photocell (35 ml) is used. The rate of this photodegradation has been measured by monitoring concentration of Cl− ion, pH, conductivity of the solution and change in the absorption spectra of compound during irradiation. The effect of various parameters, including semiconductors (TiO2, ZnO, TiO2/VxSy), organic sensitizers (p-nitrophenol, hydroquinone, riboflavine), H2O2 concentrations and radiation sources (UV, visible and sunlight), has been studied and new experimental optimized conditions have been established. ing to the experimental and kinetic results, the photocatalytic degradation reaction is followed up first order, and possible mechanisms are suggested.