Sulfuric acid leaching and recovery of vanadium from a spinel concentrate beneficiated from stone coal ore

In order to recover vanadium from vanadium-bearing black shale efficiently, a hydrometallurgical process is developed in this paper to treat the concentrate beneficiated from stone coal ore, in which the vanadium mainly occurs in the form of Fe3-xVxO4 spinel. At the first step, the leaching behaviors of Fe and V from the concentrate by using sulfuric acid solution are investigated in detail. The extraction rates of vanadium and iron could reach 92.5% and 98.5% respectively under the optimum leaching conditions of leaching temperature of 90 degrees C, sulfuric acid concentration of 25 wt%, leaching time of 90 min, L/S mass ratio of 30 and stirring speed of 600 rpm. Secondly, the iron impurity in the pregnant solution is removed efficiently by the precipitation method with Fe2O3 as nucleating agent. The effect of pH value, the amount of Fe2O3 nucleating agent and the precipitating time on the removal of iron and losing of vanadium are systematically investigated, and thereby > 99.7% iron impurity can be removed with the loss rate of vanadium not higher than 2.5%. Finally, vanadium is precipitated from the purified leach solution as ammonium poly-vanadate by adding ammonium sulfate, and then the product of V2O5 is obtained by calcining the ammonium poly-vanadate. The purity of V2O5 powder can reach 92.0% approximately.