High-chromium vanadium residue (HCVR (HCVR: high-chromium vanadium residue)) is an important secondary resource of valuable metals such as vanadium (V), chromium (Cr), and molybdenum (Mo). The mainstream technology for the utilization of HCVR, the Na₂CO₃-assisted-roasting–water-leaching method, usually requires roasting temperatures of more than 800 °C and results in the synchronous leaching of Cr with V and Mo. This makes the subsequent separation of V, Mo, and Cr in the aqueous system difficult. In this study, an efficient and clean process for the selective separation of Cr and stepped recoveries of V and Mo from HCVR is proposed via K₂CO₃-mediated carbonation conversion. Using this process, the roasting temperature can be reduced from more than 800 °C to 200 °C, and 83.14%, 99.94%, and 0.33% of V, Mo, and Cr, respectively, can be leached. Further, using the weakly alkaline ammonium-salt and sulfide precipitation methods, 98.28% pure V₂O₅ and 98.65% pure MoS₂ can be obtained and the recoveries of V and Mo can reach 82.47% and 98.88%, respectively. While almost all Mo can be recovered from the HCVR, Cr and some V might be present as a stable ferrochrome spinel in the tailing, which may be returned to the main process for the extraction of V and Cr from vanadium slag. Thus, K₂CO₃ might be a more effective alternative to Na₂CO₃ for the separation and recovery of V and Mo from HCVR and, hence, may enable its more efficient utilization.

The mixing tank is important equipment for industrial applications in the wet vanadium extraction process, but in practice, there are problems, such as uneven mixing of minerals. In this study, the effect of different types of impellers and different mixing tank structures on the suspended mass of particles was simulated using the discrete element method and volume of fluid method (DEM-VOF). The simulation results show that the round-bottomed tank performed mixing better than the flat-bottomed tank at different particle densities, and the flat-bottomed tank was prone to particle stratification and other phenomena. The round-bottomed mixing tank could better improve the solid–liquid suspension effect. In this study, the coefficient of variation σ was introduced to characterize the suspended mass of particles. By monitoring the σ value, it was found that the blade pitch angle 45 (BPA45) had the best mixing uniformity in the inclined pitched blade turbine (PBT). As the PBT impeller pitch angle increased, the particle suspension increased. When comparing different types of impellers, the Rushton exhibited a 45% improvement in mixing uniformity relative to the BPA45. Second, the width and height of the trough bottom projection were optimized and their σ values were calculated separately for different parameter conditions. The width of 0.05 m and height T/4 (T being the diameter of the tank) were finally determined to be the optimum parameters for the optimal design of the vanadium shale leaching mixing trough.

During pressure acid leaching process of black shale-hosted vanadium, increasing the reaction interface of muscovite dissolution can enhance the vanadium release. In this paper, calcium sulfate (CaSO₄) deposition behavior and its effect on muscovite under K₂SO₄ assistance were focused on for demonstrating the function of CaSO₄ on vanadium leaching from the black shale. Results showed that as K₂SO₄ mediated, the apparent activation energy of vanadium leaching and the apparent reaction order of sulfuric acid decreased from 24.37 kJ/mol to 16.63 kJ/mol and 2.7 to 1.9, respectively. The leaching rate and dependence on pH value were modified. The vanadium leaching acceleration owed to CaSO₄ deposition on muscovite in the black shale. The ion absorption stimulations found that Ca²⁺ is confirmed to be easily absorbed on the six-membered ring cavity of silicon-oxygen tetrahedrons in muscovite structure prior to K⁺ and Na⁺. Meanwhile, SO₄²⁻ provides two oxygen atoms to bond with Ca²⁺ absorbed on muscovite (001) surface. The continuous absorption and bonding create CaSO₄ deposition on muscovite (001) surface which also involves the load transmitting. The stress load transmitting correlates to pore formation in muscovite particles. It was proved that massive micropores initiated and proliferated in the existing pores under K₂SO₄ assistance. The porosity caused by CaSO₄ deposition greatly increased the reaction interface of muscovite dissolution and accelerate internal diffusion of H⁺ to the reaction interface, which can significantly weaken the vanadium leaching dependence on acid.

Vanadium (V) was successfully extracted from a high phosphorus vanadium residue (HPVR) through a carbonation process. Vanadium within HPVR substitutes for Fe in the mineral structure of Ca₉(Fe,V)(PO₄)₇ at elevated temperatures, Na₂CO₃ reacts with V to form sodium metavanadate (NaVO₃), concurrently generating calcium carbonate (CaCO₃) through its interaction with Ca₉(Fe,V)(PO₄)₇. Subsequently, V is liberated and leached by water, dissolving in the aqueous phase as metavanadate ions (VO³⁻). Crucial factors influencing V leaching efficiency include roasting time, roasting temperature, and the amount of Na₂CO₃ utilized. Response Surface Methodology (RSM) was employed. The optimized parameters determined were as follows: a roasting temperature of 850 °C, a roasting duration of 120 min, a Na₂CO₃ dosage of 8.01%, a liquid-to-solid ratio (L/S) of 3, and a leaching time of 60 min. Under these conditions, a remarkable V leaching efficiency of 83.82% was achieved. This study underscores the viability of a simplified approach for treating solid waste containing metal slag, which not only mitigates environmental pollution but also yields valuable metals.