The kinetics of the oxidation of iron(II) by chlorate in the leaching of uranium ores

The oxidation of iron(II) is an essential step in the oxidative leaching of uranium(IV) minerals such as uraninite and one of the reagents used in practice for this oxidation is sodium chlorate. This paper presents the results of an investigation into the kinetics of the oxidation of iron(II) by chlorate in solutions typical of the leaching of uranium. The results have confirmed the known form of the rate equation which is first-order in each of iron(II), chlorate and acid concentration. An overall rate equation has been derived which can be used to model the rate of iron(II) oxidation as a function of the reactant concentrations and the temperature. The half-life was found to be less than 1 min under typical leach conditions at the Olympic Dam operation in South Australia and this species cannot be considered to be the direct oxidant for uranium(IV) minerals.