Phase Relations of "FeO"–SiO2–CaO–V2O3 System: Basic Research on Vanadium Slag.

The lack of thermodynamic data on vanadium slag, the main raw material for vanadium extraction, limits the efficient extraction of vanadium from vanadium slag. According to the composition and smelting process of industrial vanadium slag, this study firstly investigated the phase equilibria of the "FeO"–SiO₂–CaO–16 wt pctV₂O₃ system at 1673 K and 1473 K under oxygen partial pressure of 10⁻¹⁰ atm via XRD, SEM and EPMA, based on which the phase diagrams of that at 1673 K and 1473 K were constructed. The results showed that the vanadium-enriched phases mainly consisted of V₂O₃, Fe₂VO₄, and Ca₃[Fe,V]₂(SiO₄)₃, where Ca₃[Fe,V]₂(SiO₄)₃ was generated due to the replacement of a large amount of Fe³⁺ by V³⁺ in Ca₃Fe₂(SiO₄)₃. On this basis, the phase relations of the "FeO"–SiO₂–CaO–16 wt pctV₂O₃ system were further discussed. It was found that the decrease in temperature promoted the crystallization of Fe₂VO₄ and Ca₃[Fe,V]₂(SiO₄)₃, but had an inhibitory effect on the crystallization of V₂O₃. And Fe₂VO₄ was transformed to V₂O₃ or Ca₃[Fe,V]₂(SiO₄)₃ by decreasing Fe/Si (Mass fraction of "FeO" and SiO₂). This study supplements the thermodynamic data for vanadium slag and provides a theoretical basis for the recovery of vanadium from vanadium slag. [ABSTRACT FROM AUTHOR]