Electrorefining of carbothermic and carbonitrothermic vanadium: a comparative study

Electrorefining is a very effective technique for transforming impure vanadium to a state of high purity. Besides being semi-continuous in nature, this process removes all the interstitial impurities to well below their respective tolerable limits, together with a number of commonly associated metallic impurities. Among different types of vanadium materials used for anode feed, carbothermic vanadium is not only relatively, less costly and easy to prepare, but also could be electrorefined into high purity vanadium. However, the presence of relatively high amount of carbon in the anode feed critically affects the electrorefining process resulting in lesser purity and poorer recovery of the vanadium. In the present study, a low-cost vanadium intermediate, essentially a solid solution of vanadium, nitrogen, carbon and oxygen was studied for electrorefining. The anode feed, containing ∼94% vanadium, was prepared by nitridation-cum-denitridation of a mixture, comprised of V2O5 and petroleum coke powders. The electrorefining was carried out in a LiCl–KCl–VCl2 bath at 893 K under high purity argon atmosphere. The current efficiency, vanadium recovery and purity were 90, 86, and 99.85%, respectively.