title: [Dechlorination degradation of 2,4-D by nanoscale Fe3O4].
abstract: Reductive transformation of 2,4-Dichlorophenoxyacetic acid (2,4-D) by nanoscale Fe3O4 was studied, and the effects of 2,4-D initial concentration, the dosage of nanoscale Fe3O4, pH and temperature on degradation rate of 2,4-D were investigated. The results showed that 48% 2,4-D with initial concentration of 10 mg/L was transformed within 48 h in the presence of 300 mg/L nanoscale Fe3O4. The degradation of 2,4-D was a reductive dechlorination process, and the concentration of chloride ion increased sharply with the degration of the 2,4-D. Disappearance of parent species and formation of reaction intermediates and products were analyzed by LC/MS. The transformation of 2,4-D followed a primary pathway of its complete reduction to phenol and a secondary pathway of sequential reductive hydrogenolysis to 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP) or 2-chlorophenol (2-CP) and phenol. The degradation equations of 2,4-D by nanoscale Fe3O4 conformed to pseudo-first-order kinetics, and the reaction rate constant (K) of 4-CP, 2,4-DCP and phenol were 0.0043 h(-1), 0.0026 h(-1) and 0.0032 h(-1), respectively. The degradation rate increased with an increase in initial concentration of 2,4-D from 0 mg/L to 10 mg/L, and increasing the dosage of nanoscale Fe3O4 from 0 mg/L to 300 mg/L. The pH of reaction solution significantly influenced reductive degradation of 2,4-D, and the optimum pH value was 3.0. Besides, high temperature could improve dechlorination rate of 2,4-D.
authors.affiliation: School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China. fangguodong1983@yahoo.cn
authors.forename: Guo-Dong
authors.initials: GD
authors.lastname: Fang
authors.forename: You-Bin
authors.initials: YB
authors.lastname: Si
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry / Q000302:isolation & purification*; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry / Q000302:isolation & purification; D053768:Metal Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical; D015084:2,4-Dichlorophenoxyacetic Acid; D052203:Ferrosoferric Oxide