10.1007/s10975-008-1005-6

Abstract

The kinetics of iron(II) sulfate oxidation with molecular oxygen on the 2% Pt/Sibunit catalyst was studied by a volumetric method at atmospheric pressure, T = 303 K, pH 0.33-2.4, [ FeSO 4 ] = 0.06-0.48 mol/l, and [ Fe 2 (SO 4 ) 3 ] = 0-0.36 mol/l in the absence of diffusion limitations. Relationships were established between the reaction rate and the concentrations of Fe 2+ , Fe 3+ , H + , and Clions in the reaction solution. The kinetic isotope effect caused by the replacement of H 2 O with D 2 O and of H + with D + was measured. The dependence of Fe 2+ and Fe 3+ adsorption on the catalyst pretreatment conditions was studied. A reaction scheme is suggested, which includes oxygen adsorption, the formation of a Fe(II) complex with surface oxygen, and the one-electron reduction of oxygen. The last step can proceed via two pathways, namely, electron transfer with H + addition and hydrogen atom transfer from the coordination sphere of the iron(II) aqua complex. A kinetic equation providing a satisfactory fit to experimental data is set up. Numerical values are determined for the rate constants of the individual steps of the scheme suggested.