Competitive extraction behaviors of vanadium and chromium in the sodium roasting — Water leaching process

The separation of vanadium and chromium from vanadium-chromium slag constitutes the greatest bottleneck in the exploitation and utilization of high-chromium vanadium-titanium magnetite, which mainly results from the insufficient understanding of the behavior of similar elements vanadium and chromium during the extraction process. In this research, a series of spinels FeV x Cr 2- x O 4 (0 ≤  x  ≤ 2) were synthesized via the high-temperature solid-state method, and their sodium roasting and leaching behavior were comprehensively analyzed. The transformation rules of sodium vanadate and chromate were investigated by XRD, SEM-EDS, FTIR, and thermodynamic calculation. The results indicate that in the FeV x Cr 2- x O 4 (0 ≤  x  ≤ 2) − Na 2 CO 3 system, at 300°C, a portion of chromium spinel phase is preferentially and slowly oxidized to Cr 2 O 3 , while the vanadium spinel rapidly oxidizes to form NaVO 3 at 400°C. Above 500°C, NaVO 3 further reacts with Na 2 CO 3 to form Na 4 V 2 O 7 , and Na 2 CrO 4 also begins to form concurrently. As the proportion of Cr in FeV x Cr 2- x O 4 increases, both the leaching efficiencies of vanadium and chromium from the sodium-roasted samples decrease, with the leaching efficiency of chromium decreasing more significantly. Significant competitive and synergistic effects between vanadium and chromium are observed in the roasting of FeV x Cr 2- x O 4 with Na 2 CO 3 . This study is expected to provide theoretical support for the development of efficient vanadium-chromium extraction processes.