title: Effects of combined and sequential addition of dual oxidants (H2O2/S2O8(2-)) on the aqueous carbofuran photodegradation.
abstract: Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) (CBF) is a widely used insecticide. Traditional methods like hydrolysis and direct photolysis cannot remove CBF effectively. In this study, the photodecay of 0.1 mM CBF in UV/H2O2, UV/S2O8(2-), and UV/H2O2/S2O8(2-) and sequential addition of a second oxidant were studied under UV light at 254 nm. The degradations of CBF follow pseudo-first-order decay kinetics. Direct photolysis was slow, but the corresponding degradation rate was increased with the addition of hydrogen peroxide (H2O2) or potassium peroxydisulfate (K2S2O8). In the UV/H2O2 reaction, the optimum reaction rate was 0.9841 min-1 at 10 mM H2O2 (pH 7); however, retardation is observed if H2O2 is overdosed. Such retardation is not observed in the UV/S2O8(2-) system, but a nonlinear increment of removal efficiency is identified. The UV/H2O2/S2O8(2-) process on the other hand shows the best performance in CBF degradation, but it has a less effective mineralization than that of the sole UV/S2O8(2-) reaction.
authors.affiliation: Department of Civil and Structural Engineering, Research Centre for Environmental Technology and Management, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
authors.forename: Wei
authors.initials: W
authors.lastname: Chu
authors.forename: Tim K
authors.initials: TK
authors.lastname: Lau
authors.forename: Sai C
authors.initials: SC
authors.lastname: Fung
mesh_terms: D002235:Carbofuran / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000008:administration & dosage*; D006863:Hydrogen-Ion Concentration; D007306:Insecticides / Q000737:chemistry*; D007700:Kinetics; D016877:Oxidants / Q000008:administration & dosage*; D010777:Photochemistry; D017680:Potassium Compounds / Q000008:administration & dosage*; D013431:Sulfates / Q000008:administration & dosage*
chemical_list: D007306:Insecticides; D016877:Oxidants; D017680:Potassium Compounds; D013431:Sulfates; C009007:potassium persulfate; D006861:Hydrogen Peroxide; D002235:Carbofuran