Oxidation of Iron(II) Ion in Sulfuric Acid Solution by Oxygen with Activated Carbon Catalyst

Abstract

The kinetic study of the oxidation of iron (II) ion in sulfuric acid solution by oxygen has been carried out using activated carbon as a catalyst. The oxidation rate was found to increase with an increase of the initial concentration of iron (II) ion and of an amount of the activated carbon catalyst, but to decrease with the increase of the initial concentration of iron (III) ion or sulfuric acid. It was newly observed that the oxidation rate decreased with a further increase of the initial concentration of iron(II) ion when the activated carbon with high catalytic activity was used. No linear relations were obtained between the oxidation rate and the amount of the catalyst. It was considered that such a result was caused by insufficient input of oxygen to the reaction system due to its slow dissolving rate in the solution. The main course of the oxidation process is estimated by the following surface reactions,
It was concluded that the activated carbon could act not only as an electrode for cell reactions between iron (II) ion and oxygen and/or between iron (II) ion and hydrogen peroxide, but also a catalyst for decomposition of hydrogen peroxide. Experimental data indicate that the oxidation rate follows the rate equation,
derived from the Langmuir-Hinshellwood mechanism postulating the forementioned surface reactions as a rate-determing step.