Evaluation of Variables Determining Leaching Efficiency in Vanadium Extraction Using Alkali Roasting

Ever since its discovery, vanadium has been used in numerous fields such as steel, aerospace, and chemical industries. The extraction process of vanadium from vanadiferous titanomagnetite ore deposited in Korea was investigated using a combination of alkali roasting and water-leaching processes. The effect of Na 2 CO 3 addition on the efficiency with which the vanadium could be leached was investigated along with an X-ray diffraction analysis. To elucidate the determining factor in the alkali-roasting process, thermodynamic calculations were performed, revealing that the formation of the liquidus phase of Na 2 CO 3 enhanced the reaction between vanadium in the concentrate and sodium, resulting in a higher leaching efficiency for vanadium being attained. The thermodynamic calculation results were indirectly supported by the characteristic temperature determination through hot-stage microscope analysis. The minimum alkali-roasting temperature was determined to be 1273 K with the addition of 30-wt pct Na 2 CO 3 . After 30 min of thermal treatment, a leaching efficiency for vanadium of 75 pct was achieved, which remained constant as the thermal treatment time was increased. Finally, the effects of the leaching time and temperature on the efficiency with which vanadium and other impurities, namely, aluminum, silicon, and sodium, could be leached was analyzed by varying the leaching time. A higher leaching efficiency was attained at higher temperatures. The leaching rate of vanadium decreased considerably after 10 to 20 minutes and subsequently remained almost constant. Following the shrinking core model, the kinetic study of leaching process was carried out. Finally, the rate-controlling step was determined based on the calculated activation energy.