Recovery of vanadium from calcification roasted-acid leaching tailing by enhanced acid leaching

•Recovery and hazard-free treatment for low-grade vanadium tailings.•Atmospheric and pressurized leaching were conducted and compared.•About 91.7% of vanadium could be recovered by pressurized leaching method.•The mechanisms of the leaching processes were revealed by the combined analysis methods. Vanadium contained tailing generated from the typical calcium roasting-acid leaching process is contaminant and waste of resource. Atmospheric and pressurized leaching were conducted and compared to recover the vanadium from the vanadium tailing and improve the tailing’s environmental quality. Orthogonal experiments were designed and applied for the atmospheric leaching study. It is shown that the extraction efficiency of V changed from 29.6% to 43.5% while the extraction efficiency of Fe, Cr, Ti, Mg remained stable under 4% with variable atmospheric leaching conditions. In the pressurized leaching experiments, the effects of leaching temperature, H2SO4 concentration, liquid to solid ratio and leaching time on the extraction of V, Fe, and Ti were investigated. Under the optimum conditions (the temperature of 413.15 K, H2SO4 concentration of 300 g/L, liquid to solid ratio of 8:1 mL/g and the reaction time of 100 min), the extraction efficiencies of V, Fe, and Ti reached 91.7%, 60.1% and 46.5% respectively, a leach residue contains only 0.13% of stable vanadium was obtained.