Process mineralogical characterization and vanadium extraction from vanadium-bearing shale by oxidation roasting-acid leaching

Abstract

• Modern technology was used to study mineralogical characteristics of V-bearing shale. • The key to vanadium extraction is to destroy the lattice of mica and oxidize V(III). • Oxidation roasting is an optimal process for V-bearing shale with complex structure. • After roasting, the holes and cracks will enlarge and improve vanadium leaching rate. Vanadium, as an important rare metal, was listed as national strategic metal in the 14th Five-Year Plan of China. Vanadium-bearing shale is a unique resource in China and the reserve of vanadium in its accounts for 87% of the total. However, the production processes for vanadium-bearing shale ores from various origins are different due to the difference in mineral composition, the occurrence of vanadium, and the embedded relationship of main minerals. Analyzing their process mineralogical characterization is key to selecting an efficient vanadium extraction process. Therefore, in this work, we systematically studied the mineralogical characteristics of vanadium-bearing shale from Shaanxi province. Analysis results of process mineralogical showed that vanadium was the most valuable element for recovery, with a grade of 1.67%. Mica was the main vanadium-bearing mineral and coexisted closely with limonite, kaolinite, quartz, and feldspar. In the mica, vanadium generally presented the trivalent state of form. According to the analysis of mineralogical characterization, the process of “oxidation roasting-acid leaching” was used to extract vanadium from the shale ore. Under the condition of roasting temperature 900 °C, roasting time 3 h, air flow 600 mL·min-1, leaching temperature 25 °C, leaching time 4 h, leaching acid dosage 10 wt% and the liquid–solid ratio of 2:1, vanadium leaching rate was 75.24%. After oxidation roasting, the lattice of mica was destroyed, and the distribution of V(Ⅴ) increased from 0 to 89.68%. Meanwhile, holes and cracks appeared on the surface of mica particles, which promoted the contact between vanadium and acid, and improved the leaching efficiency of vanadium. Therefore, a link between process mineralogical characterization and selection of vanadium extraction process could be developed, which would be helpful in the efficient utilization of vanadium-bearing shale resources.