Kinetics and mechanism of the oxidative degradation of parathion by Ferrate(VI)

Abstract

The degradation of parathion (PTH) by ferrate(VI) was investigated to evaluate the potential application of this iron-based chemical oxidant in water treatment. A series of kinetic experiments were conducted to examine the effects of operational parameters like solution pH, oxidant dose and temperature, and water constituents including anions (Cl−, NO3−, HCO3−), cations (Ca2+, Mg2+, Cu2+, Fe3+), and humic acid (HA). The removal of PTH at an initial concentration of 5 mg/L could reach 99% in 300 s under the conditions of [Fe(VI)]:[PTH] = 15:1; T = 25 °C and pH = 7.0. The presence of HCO3−, Ca2+, Cu2+, Fe3+ and HA decreased the removal efficiency of PTH, while Cl−, NO3− and Mg2+ had no obvious effects on PTH removal. Moreover, real water samples were also used to explore the feasibility of this Fe(VI) oxidation method. Fe(VI) could attack the PS double bond, and the PO single bond connecting the nitrophenol or the ethyl group in PTH molecule, leading to the formation of six products (paraoxon, thiophosphates and phosphates), which were detected by liquid chromatography-time-of-flight-mass spectrometry (LC-TOF-MS). These findings may provide useful information for the environmental elimination of organophosphate pesticides.