Catalytic decomposition of hydrogen peroxide by Fe(III) in homogeneous aqueous solution: Mechanism and kinetic modeling

This paper describes a kinetic model for the decomposition of hydrogen pero xide by ferric ion in homogeneous aqueous solution (pH < 3). The reaction w as investigated experimentally at 25.0 degrees C and I = 0.1 M (HClO4/NaClO 4), ina completely mixed batch reactor and under a wide range of experiment al conditions (1 less than or equal to pH less than or equal to 3; 0.2 mM l ess than or equal to [H2O2](0) less than or equal to 1 M; 50 mu M less than or equal to [Fe(III)](0) less than or equal to 1 mM; 1 less than or equal to [H2O2](0)/ [Fe(III)](0) less than or equal to 5000). The results of this study demonstrated that the rate of decomposition of hydrogen peroxide by Fe(III) could be predicted very accurately by a kinetic model which takes i nto account the rapid formation and the slower decomposition of Fe(III)-hyd roperoxy complexes (Fe-III[(HO2)(2+) and Fe-III(OH)(HO2)(+)). The rate cons tant for the unimolecular decomposition of the Fe(Ill)-hydroperoxy complexe s was determined to be 2.7 x 10(-3) s(-1). The use of the kinetic model all ows a better understanding of the effects of operational parameters (i.e., pH and [H2O2](0)/ [Fe(III)](0)) on the complex kinetics of decomposition of H2O2 by Fe(III).