Catalytic degradation of propetamphos and azamethiphos using silver ion.

In this study, the degradation of two organophosphate pesticides, namely, propetamphos and azamethiphos, in the presence of Ag at different mole ratios was investigated. Moreover, the kinetic and degradation pathways of both chemicals in the range of 0-60 min were explored. Gas chromatography equipped with a thermionic specific detector was used to investigate the pesticide degradation kinetics and mechanism. The results show that the degradation rate of both pesticides follows first-order kinetic. The first-order rate constant and the half-life of reaction were in the range of 0.002-0.143 min, 187-2.1 min, and 0.005-0.164 min and 60-1.8 min, for propetamphos and azamethiphos, respectively, at ambient temperature (25 ºC). Because group containing sulfur atom is a better leaving group than group containing nitrogen, the rate of degradation of azamethiphos is higher than propetamphos. In a higher mole ratio of Ag to pesticides, the degradation rate was increased, and it is possible to predict the rate of degradation of pesticides according to the chemical composition of leaving group.