Catalytic decomposition of hydrogen peroxide by ferric ion in dilute sulfuric acid solutions

Abstract

Hydrogen peroxide decomposition in acidic solutions is catalyzed by the free ferric ion, Fe3+. The following rate law for this reaction is determined by the initial rate method in solutions similar to those used for acidicin situ uranium leaching:\( - (dm_{H_2 O_2 } /dt)_{25^\circ C} = k\frac{{(m_{H_2 O_2 } )(m_{Fe} 3 - )}}{{(m_H - )}}\) wherek = 4.3 × 10−3 s°1 at 25 °C. From 25° to 50 °C, the activation energy is 85.6 kJ/mol. The decomposition of hydrogen peroxide proceeds by a particular redox reaction sequence that depends on the ratio of the concentrations of hydrogen peroxide to free ferric ion. The rate law determined here is consistent with the form derived from the redox sequence for the case where the ratio of hydrogen peroxide to free ferric ion concentration is greater than 1.0. The magnitude of the rate constant indicates that the decomposition of hydrogen peroxide may cause rapid loss of this oxidant in leaching solutions containing ferric ion.