Manganese Recovery from Vanadium Converter Slags after Leaching of Vanadium

A new technology for the production of pure vanadium pentoxide from manganese vanadium-containing metallurgical slags is being developed at the Institute of Metallurgy (Ural Branch, Russian Academy of Sciences). Solid residues (cakes) containing 7-10% Mn, which seems reasonable to extract, form due to selective vanadium recovery from the calcined slags. The study of the mineralogical content of the cakes shows that manganese exists in the cakes in the form of MnCO3. An aqueous solution of sulfuric acid is used as a leaching agent. According to the data obtained, the maximum solubility of manganese sulfate is 484-500 g/dm(3) at t = 25 degrees C and the H2SO4 concentration is 5 g/dm(3). Taking into account these data, the leaching of manganese from the cakes with aqueous solutions of H2SO4 is studied. The manganese recovery from the cakes to the solution is 75%, and the additional recovery of vanadium remained in the cakes is up to 50%. The complex solutions formed by leaching contain impurities of Fe3+, V5+, Al3+, and Si4+ and are purified by supplying them onto a fresh portion of the cake. These impurities are removed at pH 4-4.5. Manganese precipitates from solutions using ammonium carbonate (NH4)(2)CO3 to form MnCO3. The washed and calcined precipitate contains pure Mn3O4. A principal technological scheme for the combined processing of manganese-containing vanadium slags is presented. The technology developed provides the recovery of V2O5, Mn3O4, MgO, and (NH4)(2)SO4 from a solution, and complex master alloys form from the solid residues.