Catalytic degradation of propetamphos and azamethiphos using silver ion

Abstract

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^-1, 187-2.1 min, and 0.005-0.164 min^-1 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.

Keywords: Azamethiphos; Degradation; Hydrolysis; Organophosphate; Propetamphos; Silver ion.