Oxidation of dichlorvos by UV/hydrogen peroxide process

The objective of this study was to explore the oxidation of dichlorvos, an insecticide, with UV/H2O2 process. Batch experiments were carried out to investigate the efficiency of initial dichlorvos concentration, initial pH, hydrogen peroxide concentration, light intensity, and electrolytes on the oxidation of dichlorvos. By kinetic analysis, it was found that the initial rate of dichlorvos oxidation is independent of initial pH range 3-8. The rates of dichlorvos oxidation were similar because in all cases the solution pH dropped down to around 3. The rate of dichlorvos oxidation increased with increasing hydrogen peroxide concentration as well as light intensity used in this study. In the presence of phosphate and nitrate ions, inhibition of dichlorvos oxidation could be expected. The rate of dichlorvos oxidation was reduced due to the competition of hydroxyl radicals by phosphate ions, which also induced consumption of hydrogen peroxide. UV light could be absorbed by nitrate ions, leading to the reduction of UV light absorption by hydrogen peroxide. Under this condition, the rate of hydroxyl radical generation with nitrate ions was not as high as that with other salts.