Photo-fenton assisted reaction of dimethoate in aqueous solutions

The photo-Fenton reaction of an organophosphorus insecticide, dimethoate (O,O-dimethyl methylcarbamoylmethyl phosphorodithioate), was studied by following the identification and determination of the decomposition products and the total carbon removal rate. The reactions were performed in a batch recycle reactor, at room temperature, using UV radiation, H2O2 as oxidant, and FeCl3 x 6H2O as catalyst. The oxidation results were determined with a total organic carbon (TOC) analyzer and ion chromatography. The presence of reaction products was identified by gas chromatography-mass spectrometry (GC-MS). Apart from the sulfate, phosphate, and ammonium ions, the presence of dimethyl phosphite, N-methyl-acetamide, and formic acid was also detected. Excess of H2O2 concentration did not influence the reaction rate. The expression for the total carbon removal was assessed and the TOC removal rate constants were calculated.