Advanced oxidation for the treatment of chlorpyrifos in aqueous solution

Chlorpyrifos is an organophosphate pesticide and is significant because of its extensive use, persistence in the environment, wide distribution, and its toxicity may lead to lung and central nervous system damage, developmental and autoimmune disorders and vomiting. In the present study, the irradiation of chlorpyrifos in aqueous solution by 60Co gamma-rays was conducted on a laboratory scale and the removal efficiency of chlorpyrifos was investigated. The SPME-GC-ECD method was used for analysis of chlorpyrifos. Aqueous solutions of different concentrations of target compound (200-1000 mu g L-1) were irradiated through 30-575 Gy. Gamma irradiation showed 100% degradation for a 500 mu g L-1 solution at an absorbed dose of 575 Gy (the dose rate was 300 Gy h(-1)). The radiolysis of chlorpyrifos was pseudo-first order (decay) with respect to dose. The dose constants determined in this study ranged from 8.2 x 10(-3) to 2.6 x 10(-2) Gy(-1), and decreased with an increase in the initial concentration of chlorpyrifos, while the radiation chemical yield (G-value) for the loss of chlorpyrifos was found to decrease with increasing absorbed dose. The effect of saturated solutions of N-2 and N2O, and radical scavengers tert-butanol, iso-propanol, H2O2. NaNO3 and NaNO2 on the degradation of chlorpyrifos were also studied. The results showed that the oxidative center dot OH was the most important in the degradation of chlorpyrifos, while the reductive radicals, aqueous electron and H-center dot, were of less importance for the degradation of chlorpyrifos. The inorganic byproducts Cl-, SO42- and PO43- were quantitatively determined by IC. (C) 2013 Elsevier Ltd. All rights reserved.