Electrochemical degradation of the insecticide methyl parathion using a boron-doped diamond film anode

Abstract Methyl parathion is one of the most toxic of the organophosphate insecticides. While this agent continues to be used, natural waters in agricultural areas are likely to contain significant amounts of the biocide, representing a threat to beneficial insects, freshwater organisms, birds and mammals. The electrochemical oxidation of methyl parathion in acidic medium has been studied using a boron-doped diamond (BDD)/Ti anode under galvanostatic current control. Chronoamperometry showed that significant oxidation of reference standard methyl parathion commenced at 1.8 V vs Ag/AgCl, while spectrophotometric studies revealed that the absorbance of a commercial formulation of the insecticide decayed according to time in electrolysis. Electrochemical degradation experiments were performed in a laboratory-constructed polypropylene cell in which solutions containing methyl parathion (equivalent to 60 mg L −1 ) were subjected to electrolytic treatment at different current densities (5, 10, 25, 50 and 100 mA cm −2 ). High performance liquid chromatographic analysis demonstrated that 81.2% of the insecticide was removed in 180 min at an applied current density of 100 mA cm −2 , and a compound, identified from its UV spectrum as 4-nitrophenol, was formed either as an intermediate or as a byproduct. Under these conditions, mineralization efficiency (determined by total organic carbon analysis) was 67.6%, and the toxicity of the original electrolyte against the bioluminescent bacterium Vibrio fischeri was reduced considerably by the electrochemical treatment. It is concluded that electrooxidation using BBD/Ti electrodes represents an appropriate method for the removal of methyl parathion from contaminated waters.