Leaching Kinetics of Vanadium from Calcium-Roasting High-Chromium Vanadium Slag Enhanced by Electric Field

Vanadium exists as multivalent valences in high-chromium vanadium slag, and it is hard to leach out in low valence. Electro-oxidation technology has been applied to enhance the leaching process of calcium-roasting high-chromium vanadium slag. The effect of parameters that affect the leaching efficiency of vanadium including concentration of sulfur acid, current density, reaction temperature, and liquid-to-solid ratio was investigated. The results showed that vanadium in low valence could be oxidized and efficiently leached out enhanced with electricity. The leaching kinetics was analyzed, which indicates that the leaching rate was controlled by the surface chemical reaction with an apparent activation energy of 40.11 kJ/mol. On the basis of this process, vanadium could be efficiently leached out with a leaching efficiency of 92.14% under optimal conditions: concentration of sulfur acid of 40 vol %, current density of 750 A/m 2 , reaction temperature of 90 °C, reaction time of 180 min, particle size under 75 μm, liquid-to-solid ratio of 4:1 mL/g, and stirring rate of 500 rpm. The relationship between the leaching efficiency and the parameters affecting the leaching process could be described as 1 - (1 - x ) 1/3 = K 0 × [H 2 SO 4 ] 0.1390 × [ J ] 0.03354 × [ T ] 2.8247 × [ L / S ] -0.2598 × exp 40.11/ T × t .