A Novel Process of Vanadium Extraction from Molten Vanadium Bearing Slag

Abstract

In this study, a novel process (melting process) of vanadium extraction from vanadium slag (V-slag) in its molten state was attempted at the laboratory scale by oxidizing slag with pure oxygen in the presence of sodium carbonate (Na2CO3). The effect of Na2CO3 content in the slag on the vanadium extraction was studied. The sintered samples were then leached by water and characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. The results showed that vanadium-rich phases, mainly NaVO3 and Na9V14O35 were formed in the melting process. About 80 % of the vanadium recovery was obtained by addition of 25 % Na2CO3 under certain leaching conditions (i.e. 85 % of the particle size <150 μm, leaching temperature 95 °C, leaching time 2 h, liquid to solid ratio 5:1 mL/g, stirring speed 500 rpm), which is in the same level comparing with the roast process. The side reactions could be easier to occur at elevated temperatures, causing more sodium salt consumption and vanadium loss. The overall vanadium loss was mainly attributed to the insufficient oxidizing reaction of V(IV) to V(V). Compared to the roast process, recovery of vanadium by the present melting process from V-slag and utilization of its heat energy are of significant importance not only for saving metal resources, but also for energy saving and emission reduction.