Photocatalytic removal of the insecticide fenitrothion from water sensitized with TiO2

The photocatalytic removal of the insecticide fenitrothion (IUPAC name: O,O-dimethyl O-4-nitro-m-tolyl phosphorothioate), C9H12NO5PS, from water suspension of TiO2, was investigated by following the disappearance of the original substance along with the formation and disappearance of intermediates via recording NMR (1H and 31P) and UV spectra, as well as by pH measurements. Based on the obtained data, a possible reaction mechanism was proposed. It was found that 31P-NMR spectrometry can be successfully used to follow the kinetics of transforming organic into inorganic phosphorus in the course of the degradation (ka=9.2×10−7 mol dm−3 min−1, r=0.980 for the illumination period after 15 h). The rate of fenitrothion aromatic ring decomposition was followed by UV spectrometry during the illumination (ka=3.1×10−6 mol dm−3 min−1, r=0.989). The complete mineralization was attained after about 66 h of irradiation.