A kinetics study of multi-stage counter-current circulation acid leaching of vanadium from stone coal

The multi-stage counter-current circulation acid leaching of vanadium from stone coal was presented to decrease sulfuric acid consumption and enhance the leaching efficiency. The main factors on multi-stage counter-current circulation acid leaching were investigated. The factors were analyzed in terms of kinetics using the shrinking core model (SCM). The results show that the vanadium recovery could reach 86% under the conditions of sulfuric acid concentration of 4 M, liquid to solid ratio of 2 mL/g, temperature of 95 °C, reaction time of 60 min, mean particle size of 125 μm and circulation acid leaching stage of three. During the four-stage acid leaching process, the KAl(SO4)2(H2O)12 could form and lead to the losses of vanadium in acid leaching solution due to the strong adsorption performance. The acid leaching process was controlled by chemical reaction with the sulfuric acid concentration under 4 M, but controlled by internal diffusion with the sulfuric acid concentration above 4 M. However, the acid leaching process was always controlled by internal diffusion at different temperatures.