Vanadium extraction from water-cooled vanadium converter slag via salt-free roasting and acid leaching

Vanadium extraction from water-cooled vanadium converter slag (VCS) is of great importance for improving the production efficiency of the vanadium industry. A clean process for extracting vanadium from water-cooled VCS is proposed. This process includes sieving, salt-free roasting, and sulfuric acid leaching. First, through sieving at 100 meshes, large particles of metallic iron are removed and vanadium is preliminarily enriched. Then, salt-free roasting at 950 degrees C for 1 h can destroy the structures of vanadium ferrospinel and fayalite completely. Vanadate (manganese vanadate, magnesium vanadate, and calcium vanadate), Fe2O3, SiO2, and Fe2TiO5 are formed in the roasted product. Mechanistic analysis shows that as the roasting temperature is increased, oxidation starts from the edges of particles. Vanadium is first oxidized into V4+ and gradually oxidized into V5+. Finally, systematic leaching experiments illustrate that under the optimal conditions, the leaching yields of V, Ca, Mn, and Mg are 94.99%, 89.24%, 46.81%, and 33.11%, respectively, whereas those of Fe, Si, and Cr are only 0.77%, 1.51%, and 1.03%, respectively. Furthermore, phase analysis demonstrates that only vanadate is selectively leached into the solution. The leaching residue does not contain alkali metals and can thus be used as raw material for iron production.