title: Kinetic modeling of 2,4-dichlorophenoxyacetic acid (2,4-D) degradation in soil slurry by anodic fenton treatment.
abstract: Anodic Fenton treatment (AFT) has been shown to be a promising technology in pesticide wastewater treatment. However, no research has been conducted on the AFT application to contaminated soils. In this study, the 2,4-D degradation kinetics of AFT in a silt loam soil slurry were investigated for the first time, and the effects of various experimental conditions including initial 2,4-D concentration, Fenton reagent delivery rate, amount of humic acid (HA) addition, and pH were examined. The 2,4-D degradation in soil slurry by AFT was found to follow a two-stage kinetic model. During the early stage of AFT (the first 4-5 min), the 2,4-D concentration profile followed a pseudo-first-order kinetic model. In the later stage (typically after 5 or 6 min), the AFT kinetic model provided a better fit. This result is most likely due to the existence of (*)OH scavengers and 2,4-D sorption on soil. The Fe(2+) delivery rate was shown to be a more significant factor in degradation rate than the H(2)O(2) delivery rate when the Fe(2+)/H(2)O(2) ratios were in the range of 1:2 to 1:10. The presence of HA in soil lowered the AFT rate, most probably due to the competition with 2,4-D for consumption of (*)OH and increased sorption of 2,4-D on soil. The optimal pH for 2,4-D degradation in soil slurry by AFT was observed to be in the range of pH 2-3.
authors.affiliation: Graduate Field of Environmental Toxicology, TXA, MVR Hall, Cornell University, Ithaca, New York 14853-4401, USA.
authors.forename: Lingjun
authors.initials: L
authors.lastname: Kong
authors.forename: Ann T
authors.initials: AT
authors.lastname: Lemley
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000032:analysis / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000032:analysis / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D012987:Soil / Q000032:analysis*
chemical_list: C045076:Fenton's reagent; D006540:Herbicides; D012987:Soil; D015084:2,4-Dichlorophenoxyacetic Acid; D006861:Hydrogen Peroxide; D007501:Iron