A clean metallurgical process for separation and recovery of vanadium and chromium from V-Cr-bearing reducing slag

In this work, a clean metallurgical process is used to separate and recover vanadium and chromium from V-Cr-bearing reducing slag. Comparing with the traditional process, the process not only reduces the use of sulfuric acid, but also saves the cost of wastewater purification. The process consists of four procedures: low temperature sulphating roasting, reduction leaching, selectively oxidizing and the oxides of vanadium and chromium preparing. Among these, the reduction leaching and selectively oxidizing are the key steps. Low temperature sulphating roasting is used to strengthen the decomposition of V-Cr-bearing reducing slag, Na2SO3 is used for the reduction of vanadium from V(V) to V(IV) or V(III), CrO3 is used to selectively oxidize the vanadium in the leached solution, (NH4)2SO4 is used to make the vanadium precipitated in the form of ammonium polyvanadate, and NaOH is used to precipitate Cr(III) from the V precipitated solution. It was found that the leaching efficiencies of Cr and V can reach 99.7% and 99.6% respectively by low temperature sulphating roasting and reduction leaching. The products of V2O5 with purity 99.1% and Cr2O3 with purity 98.9% were obtained by treating the ammonium polyvanadate and the precipitate of Cr(III), respectively.