Effect of Oxidative Pretreatment for the Dissolution of Cr-Substituted Hematites/Magnetites

• Published in: Industrial & engineering chemistry research 2002-06, Vol.41 (13), p.3053-3063
• Main Authors: Manjanna, Jayappa, Venkateswaran, Gopala
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemistry; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Inorganic chemistry and origins of life; Installations for energy generation and conversion: thermal and electrical energy; Miscellaneous; Preparations and properties
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie010344d

The presence of chromium in iron oxides such as hematite and magnetite hinders their dissolution in reductive-complexing formulations. The oxidative pretreatment (op) of such oxides, which results in Cr leaching from the oxide, has improved the dissolution when subsequently treated with a reductive-complexing formulation. In this study, various oxidative reagents such as Mn(III)−L and permanganate (acidic/alkaline) reagents were compared for their effectiveness of Cr2O3 dissolution. Because the permanganate reagents were effective for the op of Cr-substituted hematites/magnetites, the relative effectiveness of permanganate reagents can be shown as HMnO4 ≈ NP > AP. The op with permanganate reagents was found to be marginally advantageous for the reductive-complexing dissolution of Cr-substituted hematites (csh) and magentites (csm) in V(II) formulations such as vanadium(II) picolinate, vanadium(II) ethylenediaminetetraacetate, and vanadium(II) citrate. Nevertheless, the amount of chromium released during the op step was only a fraction of its original content in the oxide, and the use of higher concentrations (≥stoichiometric amounts) of oxidative reagents was not found to be advantageous. However, even this small amount of Cr removal could improve the dissolution of these oxides. The nature of the dissolution profiles of csh/csm has not varied because of the op step when compared with their dissolution profiles without the op step. The redox cycling in a typical case of 20% csh/csm has shown that the extent of dissolution can be further improved by adopting a multicycle dissolution process.