Efficient Recovery of Vanadium from Vanadium–Titanium Slag (VTS) via Calcification Roasting and Acid Leaching: Process and Mechanism

As a strategically important metal, vanadium (V) plays a crucial role in resource security, and its efficient extraction is therefore of great significance. Traditional sodium roasting processes suffer from gaseous pollutant emissions and high costs, while calcification roasting–acid leaching has emerged as an alternative due to its environmental friendliness and economic viability. This study focuses on VTS (mainly composed of FeV2O4 and Fe2SiO4), systematically optimizing the calcification roasting–hydrochloric acid leaching process and investigating its reaction mechanism. By comparing the Gibbs free energy changes of reaction products and the acid leaching process with different additives using DFT calculations, calcium oxide was selected as the optimal calcifying agent. Experimental results show that CaO significantly promotes the transformation of FeV2O4 into soluble calcium vanadate and preferentially reacts with SiO2 to inhibit vanadate encapsulation, creating a structural basis for the selective dissolution of V. Under optimal process conditions, the leaching efficiency of V can reach 94.23%. Furthermore, density functional theory (DFT) calculations substantiate that the inherently weak bonding in Ca2V2O7 facilitates its effortless dissociation during the acid leaching phase. The Douglas hierarchical decision-making method is further adopted for secondary economic potential, and this proposed method has the lowest investment risk. This study provides an experimental and theoretical basis for the efficient and clean extraction of vanadium.