A cleaner method for preparation of chromium oxide from chromite

A new leaching process for preparing chromium oxide from chromite was studied in this paper, using Cr(VI) extracted from the remediation treatment of chromite ore processing residue (COPR) as an oxidant. Thus, the “detoxification” of deposited COPR could be achieved and no new Cr(VI)-bearing substances would be generated in preparation process of chromium oxide. Thermodynamic analysis was applied and several tests were conducted. It was found that a chromite with higher Fe(II) content showed lower stability in an oxidizing solution. A general decomposition mechanism of chromite is proposed and suggests that the oxidation of ions in spinel plays a significant role in decomposing chromite. Furthermore, the extraction process of chromium from leachate was investigated. Results demonstrated that iron, magnesium and aluminum could be effectively removed via oxalic acid treatment and subsequent pH adjustment, with chromium oxide as the final product.