Non-salt roasting mechanism of V–Cr slag toward efficient selective extraction of vanadium

Abstract

Developing a clean method for the sustainable utilization of reducing slag containing vanadium and chromium (V–Cr slag) is necessary, with the non-salt roasting method exhibiting considerable potential. In this study, we conducted a detailed analysis of the mechanisms driving non-salt roasting of the V–Cr slag by investigating phase transformations, valence transition, and redistribution of vanadium and associated transition elements. Based on our findings, we performed efficient selective extraction experiments and revealed that spinel (Fe,Mn)(V,Cr)2O4, the carrier of vanadium, is converted to acid-soluble products, including VO2, Mg2V2O7, and Mn2V2O7, and acid-insoluble products, such as (Fe,Cr)2O3, TiO2, MnO2, and Fe2TiO5 at a roasting temperature of 700 °C; At roasting temperatures > 850 °C, MnO2 is converted to half Mn2V2O7 and half (Fe,Cr,Mn)2O3. Vanadium is separated from Fe, Cr, Ti, Si, and half Mn via selective leaching. Under optimized conditions, the leaching efficiency of V reached 94.55%, and those of Fe, Cr, Ti, Si, and Mn were 0.71%, 0.50%, 0.44%, 0.23%, and 50%, respectively. This study provides a technical and theoretical basis for cleaner and safer utilization of V–Cr slag.