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

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 degrees 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 P-S double bond, and the P-O 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.