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*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.

Key Words:

• Organophosphorus pesticides
• Dimethoate
• Photo-Fenton assisted reaction
• H₂O₂.