Degradation and byproduct formation of parathion in aqueous solutions by UV and UV/H(2)O(2) treatment.
The photodegradation of parathion in aqueous solutions by UV and UV/H(2)O(2) processes was evaluated. Direct photolysis of parathion both by LP (low pressure) and MP (medium pressure) lamps at pH 7 was very slow with quantum yields of 6.67+/-0.33x10(-4) and 6.00+/-1.06x10(-4)molE(-1), respectively. Hydrogen peroxide enhanced the photodegradation of parathion through the reaction between UV generated hydroxyl radical and parathion with a second-order reaction rate constant of 9.70+/-0.45x10(9)M(-1)s(-1). An optimum molar ratio between hydrogen peroxide and parathion was determined to be between 300 and 400. Photodegradation of parathion yielded several organic byproducts, of which the paraoxon, 4-nitrophenol, O,O,O-triethyl thiophosphate and O,O-diethyl-methyl thiophosphate were quantified and their occurrence during UV/H(2)O(2) processes were discussed. NO(2)(-), PO(4)(3-), NO(3)(-) and SO(4)(2-) were the major anionic byproducts of parathion photodegradation and their recover ratios were also discussed. A photodegradation scheme suggesting three simultaneous pathways was proposed in the study.
Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708-0287, USA. cw10@duke.edu
Changlong
C
Wu
Karl G
KG
Linden
D006861:Hydrogen Peroxide / Q000737:chemistry*; D007306:Insecticides / Q000737:chemistry*; D010084:Oxidation-Reduction; D010278:Parathion / Q000737:chemistry*; D012996:Solutions; D014466:Ultraviolet Rays; D014867:Water
D007306:Insecticides; D012996:Solutions; D014867:Water; D010278:Parathion; D006861:Hydrogen Peroxide