The Oxidation of Fe(II) in Acidic Sulfate Solutions with Air at Elevated Pressures. Part 1. Kinetics above 1 M H2SO4

Abstract

The oxidation of ferrous ions in acidic sulfate solutions at elevated air pressures was investigated. The effect of the Fe2+ concentration, initial H2SO4 concentration and partial oxygen pressure on the reaction rate were determined at three different temperatures, that is, T = 90, 70, and 50 °C. The effect on the reaction rate of the components that H2SO4 dissociates into, that is, HSO4–, H3O+, and SO42–, was established as well. A second order of reaction in Fe2+ and a first order of reaction in O2 were determined. No clear order in either H2SO4 or the components H2SO4 dissociates into, could be established. For the experiments with initial concentrations of H2SO4 of 1 M and higher the oxidation rate was not affected, that is, a zero order of reaction in H2SO4 for these concentrations. Therefore, the kinetic rate expression for the oxidation of Fe2+ at concentrations of H2SO4 of 1 M and higher can be calculated with RFe2+ = d[Fe2+]/dt = k[Fe2+]2PO2, where the activation energy EA was determined to be 60.3 kJ/mol.