title: Kinetics and modeling of the Fe(III)/H2O2 system in the presence of sulfate in acidic aqueous solutions.
abstract: This work examined the effect of sulfate ions on the rate of decomposition of H2O2 by Fe(III) in homogeneous aqueous solutions. Experiments were carried out at 25 degrees C, pH < or = 3 and the concentrations of sulfate ranged from 0 to 200 mM ([Fe(III)]0 = 0.2 or 1 mM, [H2O2]0 = 10 or 50 mM). The spectrophometric study shows that addition of sulfate decreased the formation of iron(III)-peroxo complexes and that H2O2 does not form complexes with iron(III)-sulfato complexes. The rates of decomposition of H2O2 markedly decreased in the presence of sulfate. The measured rates were accurately predicted by a kinetic model based on reactions previously validated in NaClO4/HClO4 solutions and on additional reactions involving sulfate ions and sulfate radicals. At a fixed pH, the pseudo-first-order rate constants were found to decrease linearly with the molar fraction of Fe(II) complexed with sulfate. The model was also able to predict the rate of oxidation of a probe compound (atrazine) by Fe(III)/H2O2. Computer simulations indicate that the decrease of the rate of oxidation of organic solutes by Fe(III)/H2O2 can be mainly attributed to the complexation of Fe(III) by sulfate ions, while sulfate radicals play a minor role on the overall reaction rates.
authors.affiliation: Laboratoire de Chimie de l'Eau et de l'Environnement, CNRS UMR 6008, Ecole Supérieure d'Ingénieurs de Poitiers, Universite de Poitiers, 86 022 Poitiers Cedex, France. joseph.delaat@esip.univ-poitiers.fr
authors.forename: Joseph
authors.initials: J
authors.lastname: De Laat
authors.forename: Giang
authors.initials: G
authors.lastname: Le Truong
mesh_terms: D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry*; D014865:Waste Disposal, Fluid
chemical_list: C045076:Fenton's reagent; D007220:Industrial Waste; D013431:Sulfates; D006861:Hydrogen Peroxide; D007501:Iron