Photo Catalytic Degradation of Chloropyrifos, Endosulphon, Imidocloprid and Quinolphos by Nano Crystalline TiO<SUB>2</SUB> – a Kinetic Study with pH and Mass Effects

Abstract

Intense and massive agricultural methods ultimately lead to accumulation of pesticides in high concentrations for long durations of time in soil. With increasing demand for vegetables and agro products a crisis on the environmental problems and propagation of pollutants through food products prevail. Novel oxidation methods involving eco-benign, cheap and reusable catalysts are required for the degradation of pesticides. In the present work, among the widely used pesticides Chloropyrifos, Quinolphos, Imidocloprid and Endosulphon are chosen for degradation studies. Titanium dioxide (TiO2) is a popular photo catalyst, with emergence of catalysis by metal oxide nanoparticles, nano crystalline TiO2 was synthesized by adopting combination of hydrothermal and sol gel method has been utilized. XRD and SEM-EDX measurements are made for size characterization of nano TiO2 and it is found to be 20±0.5 nm. Under visible light absorbance variation with time is recorded and used for the determination of kinetic parameters such as rate coefficient. Effects of pH and catalyst mass are studied. The optimum pH values for maximum rates are found to be 4.8, 5.2, 5.8 and 6.5 corresponding to Chloropyrifos, Quinolphos, Imidocloprid and Endosulphon respectively. In the absence of TiO2 such reactions did not proceed even under visible light.