Vanadium extraction from roasted vanadium-bearing steel slag via pressure acid leaching

In this study, pressure acid leaching technology was used to extract vanadium from vanadium-bearing steel slag, and the optimum parameters and mechanism for vanadium extraction were investigated. Pressure acid leaching significantly enhanced vanadium leaching from roasted vanadium-bearing steel slag. The suitable leaching conditions were liquid/solid ratio of 5:1, sulfuric acid concentration of 20%, oxygen pressure of 1.0 MPa, and leaching temperature of 160 °C. The maximum leaching rate was 87.8%, which was obviously higher than that under atmospheric acid leaching at 60 °C. Regardless of pressure acid leaching or roasting pretreatment, the increase in the oxidation degree facilitated efficient vanadium extraction from vanadium-bearing steel slag. As pressure acid leaching was employed for vanadium extraction, both the interfacial transfer and diffusion across the product layer could affect the leaching rate. The variant of the shrinking core model was more suitable for describing the leaching kinetics of vanadium, and the activation energy calculated from the apparent rate constant was 20.87 mol−1.