Novel Strategy for Green Comprehensive Utilization of Vanadium Slag with High-Content Chromium

A novel strategy for comprehensive utilization of vanadium slag with high-content chromium is proposed in the present study. This approach involves two steps: vanadium slag is first treated by the calcification roasting–sulfuric acid leaching method to extract vanadium. Then, high-carbon ferrochromium is smelted with the mixture by carbothermal reduction. In the first step, 99.41% vanadium in the vanadium slag can be enriched in the leaching liquor; however, the loss of chromium is negligible. The roasting and leaching parameters are studied. n(CaO)/n(V2O3) = 0.5, 900 °C, and 60 min are the optimum roasting conditions; 50 °C, 60 min, and sulfuric acid concentration of 20% are the optimum leaching conditions. In the second step, the chromium oxides and iron oxides are first reduced to chromium carbide and iron carbide, then further reduced to metallic chromium and iron with the increasing of temperature. The recoveries of chromium, iron, and metal reached all exceed 95.00%. The chromium content in high-carbon ferrochromium can achieve over 50%. Both the contents of impurity elements in high-carbon ferrochromium and toxic substances in reduction slag meet the expected requirements. The toxicity results show that tailings have been detoxified, and the reduced slag is harmless. This method has high extraction efficiency and is environmentally friendly.