Efficient separation of chromium and vanadium by calcification roasting–sodium carbonate leaching from high chromium vanadium slag and V2O5 preparation

[Display omitted] •Calcification roasting–Na2CO3 leaching was used to separate vanadium and chromium.•93.19% vanadium and 0.04% chromium was leached.•V2O5 with a purity of 99.68% was prepared. Calcification roasting–sodium carbonate (Na2CO3) leaching process was carried out to separate chromium and vanadium efficiently from high chromium vanadium slag (HCVS). Then vanadium existed in the form of ammonium metavanadate (NH4VO3) after precipitation from the purified leaching liquid, and highly pure V2O5 was prepared, while chromium remained in the vanadium tailings in the form of (Fe0.6Cr0.4)2O3. The effects of separation behaviors of chromium and vanadium under different roasting and leaching conditions were studied systematically. In order to elucidate the phase evolution, XRD and SEM were used during the whole process. After calcification roasting and Na2CO3 leaching, 93.19% of vanadium and 0.04% of chromium was extracted when CaO was added to HCVS in a mole rate n(CaO)/n(V2O5) of 0.5, roasted at 900 °C and maintained for 60 min. The roasted samples were added to 160 g/L Na2CO3 solution with the mass ratio of liquid to solid (L/S) of 10, then heating at 80 °C for 60 min. CaO tended to combine with vanadium and form alkali soluble calcium vanadate, while almost all of chromium was more likely to react with iron and form (Fe0.6Cr0.4)2O3. 94.00% of vanadium was then precipitated as NH4VO3 from the vanadium–containing supernatant after CO32– removing, when NH4Cl was added with the mole rate of n(NH4+)/n(V) of 6 and precipitated for 120 min at 5 °C. The purity of V2O5 was 99.68%, which was prepared by roasting NH4VO3. This process achieved the high efficiency separation of chromium and vanadium from HCVS compared with the traditional calcification roasting–acid leaching process. And the chromium-containing vanadium tailings can be used as the raw material to extract chromium and prepare Fe-Cr alloy.