Abstract:

The degradation efficiency of dichlorvos(DDVP) pesticide was conducted using a mixture of hydrogen peroxide and sodium persulfate, catalyzed by cobalt meso-tetrakis(4-sulfonatophenyl)porphyrin(CoTPPS4). Influencing factors on degradation ratio of dichlorvos were discussed, such as oxidant species, mixing ratio between oxidants, amount of additional catalyst, initial concentration of pesticide, pH value and temperature. Reaction kinetics of degradation reaction under optimized conditions was also studied. The degradation rate increased with the increases of catalyst dosage, pH (5～9) and reaction temperature as well as the decrease of initial concentration of pesticide. The results indicated that the degradation rate of 1.015 mol/L DDVP can reach to 72.8% after 7 h, when an additional volume of mixed oxidants of Na2S2O8 and H2O2(4/1, volume ratio) with 0.050 mol/L is 5 mL, the catalyst dosage is 2.4×10-3 g at pH=9, rate constant is 0.190 h-1. Kinetic studies suggest that the catalyzed oxidative degradation of dichlorvos is a pseudo-first-order reaction with the activation energy Ea of 5.052 kJ/mol.

Key words: sodium persulfate, catalytic degradation, dichlorvos, activation energy