摘要
The photocatalytic degradation of parathion using UV radiation in combination with hydrogen peroxide and titanium dioxide or iron compounds was studied. Apparent first-order rate constants (k <sub>obs</sub> ) and initial rate constants were used to describe the degradation behavior of parathion under different conditions. The addition of TiO <sub>2</sub> or iron compounds in combination with hydrogen peroxide was effective in the detoxification of parathion. The k <sub>obs</sub> and initial rate constants increased with the increase of TiO <sub>2</sub> loading from 0.1 g1 <sup>-1</sup> to 1 g1 <sup>-1</sup> . However, the degradation rates of parathion decreased when the TiO <sub>2</sub> dose was increased to 2 g1 <sup>-1</sup> . No significant difference between buffered and unbuffered solutions was observed. The addition of oxyanion oxidant can enhance the degradation rate of parathion in the order of ClO <sub>2</sub> <sup>-</sup> >IO <sub>3</sub> <sup>-</sup> >BrO <sub>3</sub> <sup>-</sup> >CIO <sub>3</sub> <sup>-</sup> . The existence of oxygen increased the initial rate of parathion in a TiO <sub>2</sub> -amended system, but has little effect on k <sub>obs</sub> . Also, the addition of iron compounds is a promising technique for the photodegradation of parathion. The rate constants for parathion ranged from 0.029 to 0.033 min <sup>-1</sup> in the iron-amended system, which corresponds to 3-fold increase relative to UV/H <sub>2</sub> O <sub>2</sub> system. Diethylphosphoric acid, p-nitrophenol, diethylmonothiophosphoric acid, O,O-ethyl p-nitrophenyl monothiophosphoric acid and oxalate were identified as intermediates and shown to be oxidized further. Moreover, oxalate and 4-nitrophenol were found to be the major intermediates in the degradation of parathion. © 1998 Elsevier Science S.A. All rights reserved.