Novel Technology for Vanadium and Chromium Extraction with KMnO(4) in an Alkaline Medium

[Image: see text] This paper focused on the oxidation–alkaline extraction process of vanadium–chromium–reducing residue. The affected parameters including reaction temperature, KMnO(4) dosage, reaction time, NaOH dosage, and liquid-to-solid ratio on the extraction process were investigated. The E–pH diagram and the thermodynamic analysis indicated that KMnO(4) was suitable for the oxidation of low-valence vanadium and chromium. Vanadium (97.24%) and chromium (56.20%) were extracted under the following optimal reaction conditions: reaction temperature of 90 °C, reaction time of 90 min, dosage of KMnO(4) at m(KMnO(4))/m(residue) = 0.40, dosage of NaOH at m(NaOH)/m(residue) = 0.30, and liquid-to-solid ratio at 5:1 mL/g. The extraction process of vanadium was controlled by the reactant through the solid product layer and the extraction kinetics behavior fitted well with the shrink core model with an E(a) of 15.37 kJ/mol. At the same time, the surface chemical reaction was the controlling step for chromium extraction, which was difficult with an E(a) of 39.78 kJ/mol.