Recovery of tailings from the vanadium extraction process by carbothermic reduction method: Thermodynamic, experimental and hazardous potential assessment.

A cleaner process is tremendously required to deal with the vanadium tailings, which may cause serious environmental problem due to the high content of water soluble hazardous elements such as V and Cr. This problem can be possibly solved by proposed high temperature reduction-magnetic separation process, in which, V, Cr and Fe can be recycled as ferroalloy. The thermodynamic calculation results reveal that a higher temperature (>1127.8 °C) promotes the reduction of Fe, V and Cr, and improves the recovery rates of V and Cr in liquid iron. The reduction behavior of vanadium tailings was investigated using XRD, TG/DSC, SEM, EDS and ICP-OES techniques. The EDS results show that a small portion of V was remained in the slag phase when roasted at 1300 °C, while nearly all of V and Cr can concentrate in ferroalloy at 1400 °C. Approximatly 90% of V and 95% of Cr recovery in magnetic fraction can be obtained for the magnetic separation step. A small portion of V and Cr is remained in the non-magnetic final tailings, however, the hazardous potential assessments results indicate that such kind of tailings can safely use as secondary materials or stockpiled as an end-waste.