Separation and recovery of vanadium and chromium from acidic leach solution of V-Cr-bearing reducing slag

The separation and recovery of vanadium and chromium from an acidic V-Cr-bearing reducing slag leach solution was investigated by selective oxidation of V(IV) using manganese dioxide, followed by precipitation of V(V) and Cr(III), respectively. The potential-pH diagrams for vanadium-manganese-water systems and chromium-manganese-water systems were drawn. E(MnO2/Mn2+) is higher than E(VO2+/VO2+) but lower than E(Cr2O72−/Cr3+), which proves manganese dioxide can be used to selectively oxidize V(IV). The oxidation of V(IV) can reach 99.5% at a temperature of 95 °C for a oxidation duration of 3 h with the addition of 40 g/L manganese dioxide, and Cr(III) cannot be oxidized. The V(V) in the oxidized solution was precipitated in the form of ammonium polyorthovanadate and Cr(III) was precipitated as chromic hydroxide. The overall recovery of vanadium and chromium from the acidic leach solution was 98.7% and 99.4%, respectively.