Reactivity of hydrogen peroxide towards Fe3O4, Fe2CoO4 and Fe2NiO4

The kinetics of CRUD oxidation by H2O2 has been studied using aqueous suspensions of metal oxide powder. Fe3O4, Fe2CoO4 and Fe2NiO4 were used as model compounds for CRUD. In addition, the activation energies for the reaction between H2O2 and the three CRUD models were determined. The rate constants at room temperature were determined to 6.6 (±0.4) × 10−9, 3.4 (±0.4) × 10−8 and 1.6 × 10−10 m min−1 for Fe3O4, Fe2CoO4 and Fe2NiO4, respectively. The corresponding activation energies are 52 ± 4, 44 ± 5 and 57 ± 7 kJ mol−1, respectively. The mechanism of the reaction is briefly discussed indicating that the final solid product in all three cases is Fe2O3. In addition to the experimental studies, the theoretical grounds for kinetics of reactions in particle suspensions are discussed. The theoretical discussion is also used to explain the somewhat unexpected trends in reactivity observed experimentally.