A Method to Extract Vanadium from HIsmelt Reduction Slag: In Situ Sodium Salt Oxidation and Alkali Leaching

The HIsmelt smelting reduction process is an efficient direct reduction process for smelting vanadium titanomagnetite ores. About 80% vanadium is enriched in the reduction slag, however, due to the low vanadium and high calcium content in reduction slag, it is difficult to extract the vanadium economically. In this study, a process featuring in situ sodium salt oxidation and alkali leaching was proposed to extract vanadium. Efficiently in situ sodium salt oxidation process was achieved by adding sodium salts to the molten reduction slag, which was freshly discharged from HIsmelt SRV furnace. The equilibrium phases of the slag after the introduction of sodium salts were calculated and simulated by thermodynamic software. The vanadium containing phase was detected used XRD and SEM–EDS analysis. For the leaching process, the effects of NaOH concentration, temperature, particle size, liquid–solid ratio (mass ratio), and stirring speed were investigated. The optimal reaction conditions were confirmed to be the mass fraction of Na 2 CO 3 of 10 wt%, the oxygen pressure of 0.5 MPa, oxygenation time of 10 min, the temperature of 90 °C, the liquid–solid ratio of 4:1, the stirring speed of 500 rpm, the mass concentration of NaOH of 35 wt%, and the reaction time of 240 min. The final vanadium extraction rate reached 85.5% under optimal conditions. Kinetic analysis indicated that the internal diffusion was the controlling step of the leaching reaction, and the apparent reaction activation energy value was calculated to be 18.34 kJ/mol. This method is expected provide an attractive approach to extract vanadium from HIsmelt reduction slag with low energy consumption. Graphical Abstract