Separation and recovery of sulfuric acid from acidic vanadium leaching solution of stone coal via solvent extraction
Abstract The separation and recovery of sulfuric acid from an acidic leaching solution of stone coal containing 110 g/L of H2SO4 and 1.98 g/L of vanadium and other metal ions with the use of TEHA was investigated. Vanadium valence has a significant effect on the separation of sulfuric acid and vanadium because of the speciation of the anion VO2SO4 of V(V) in the solution. V(IV) almost has no effect on sulfuric acid separation from vanadium because V(IV) exists as VO2+ in the acidic leaching solution, and the influence of vanadium on sulfuric acid recovery can be decreased by reducing V(V) to V(IV) with Na2SO3. Acid extraction rate increases with an increase in TEHA concentration and O/A phase ratio but decreases with an increase in temperature. Under optimized conditions, sulfuric acid extraction capacity is 86.25 g/L of sulfuric acid with 40% TEHA and a phase ratio (O/A) of 2:1 in a 10 min phase contact at 25 degC. The raffinate containing only 12.74 g/L of sulfuric acid can be directly used for vanadium extraction. Approximately 99% of sulfuric acid could be stripped with hot water at 65 degC and an O/A ratio of 1/3 in a three stage extraction process.