title: Kinetics and mechanism for degradation of dichlorvos by permanganate in drinking water treatment.
abstract: The degradation kinetics and mechanism of dichlorvos by permanganate during drinking water treatment were investigated. The reaction of dichlorvos with permanganate was of second-order overall with negligible pH dependence and an activation energy of 29.5 kJ x mol(-1). At pH 7.0 and 25 degrees C, the rate constant was 25.2+/-0.4M(-1)s(-1). Dichlorvos was first degraded to trimethyl phosphate (TMP) and dimethyl phosphate (DMP) simultaneously which approximately accounted for <5% and >or=95% with respect to phosphorus mass, respectively. Further oxidation of DMP generated a final byproduct, monomethyl phosphate (MMP). MMP was for the first time identified as a major byproduct in chemical oxidation of dichlorvos. The kinetic model based on degradation mechanism and determined reaction rate constants allowed us to predict the evolution of dichlorvos and its byproduct concentrations during permanganate pre-oxidation process at water treatment plants. These results suggest that even though the dichlorvos concentration in surface water complies with the surface water quality standards of China (50 microg L(-1)), its concentration after conventional water treatment will most probably exceed the drinking water quality standards (1 microg L(-1)). Moreover, luminescent bacteria test shows that the acute toxicity of dichlorvos solution evidently increased after permanganate oxidation.
authors.affiliation: Research Center for Eco-Environmental Sciences (RCEES), Chinese Academy of Sciences, 18 Shuang-qing Road, Hai-dian District, Beijing 100085, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Qiang
authors.forename: Craig
authors.initials: C
authors.lastname: Adams
authors.forename: Fang
authors.initials: F
authors.lastname: Tian
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
mesh_terms: D001419:Bacteria / Q000187:drug effects; D004006:Dichlorvos / Q000737:chemistry* / Q000633:toxicity; D052918:Environmental Restoration and Remediation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D017895:Manganese Compounds / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D013696:Temperature; D018675:Toxicity Tests; D018508:Water Purification / Q000379:methods*
chemical_list: D017895:Manganese Compounds; D010087:Oxides; C048856:permanganic acid; D004006:Dichlorvos