Kinetic studies of catalytic photodegradation of chlorpyrifos insecticide in various natural waters

The photocatalytic transformation of the insecticide chlorpyrifos O,O-diethyl-O-(3,5,6-trichloro-2-pyridinyl) phosphorothioate have been studied in different types of natural waters such as lake, river, ground as well as in distilled and drinking water under natural sun light and simulated irradiation sources. Physico-chemical properties of the natural water were determined which were chosen as the major indicators (namely pH, electric conductivity, turbidity, Cl−, Na+, K+, NO3−, SO42−, PO43− and NH4+). Kinetic experiments were monitored using high performance liquid chromatography connected with UV-spectrophotometer detector. It was found that the photocatalytic degradation in all systems used in this work exhibited pseudo-first-order kinetics. The degradation rate constants were always higher for the heterogeneous catalysis in a system (TiO2/UV) compared to the systems (radiation alone, TiO2/visible or TiO2/sun).