Effective degradation of fenitrothion by zero-valent iron powder (Fe0) activated persulfate in aqueous solution: Kinetic study and product identification

Abstract

Fenitrothion (FNT), a common organophosphorus pesticide, has been regarded as a contaminant because it is adverse to the environment. In this study, we chose the highly effective technique, persulfate (PS) activation by zero-valent iron powder (Fe0), to degrade FNT. The effects of several experimental parameters including PS and Fe0 dosages, pH, temperature, and common natural water constituents were systematically investigated via kinetics studies. We found that the addition of Fe0 significantly enhanced the FNT degradation by PS under any of the studied conditions. Under the optimal conditions of [FNT]:[PS] = 1:500 (molar ratio), Fe0:PS = 1:1.5 (molar ratio), pH = 3.0, and 35 °C, 10 mg L−1 of FNT could be completely degraded in 45 min and 20 μg L−1 FNT was removed 96 ± 0% in 12 h. Sulfate (SO4−) radicals led the degradation of FNT in the Fe0/PS system. Twelve transformation products of FNT were determined by LC-MS/MS analysis, and the vulnerable sites in FNT were predicted by a density-functional-theory-based descriptor, 2∑(CriHOMO)2, to illustrate the generation of initial reaction products. The overall acute and chronic toxicity of FNT and its products, as predicted by the ecological structure–activity relationship model (ECOSAR), decreased in the Fe0/PS process. The present work proves that FNT could be efficiently degraded by Fe0-activated PS, which may also contribute to future research on the removal of other organophosphorus pesticides.