Separation of Na 3 VO 4 and Na 2 CrO 4 from high alkalinity solutions by solvent extraction

Purification of vanadium products by removal of chromium compounds, especially at high pH, remains a challenging task. In this contribution, purification of sodium vanadate solutions by selective solvent extraction of Cr(VI) from strong alkaline aqueous solution (initial pH 12 and above) was investigated, and the mechanisms governing the selectivity of quaternary ammonium salt Aliquat 336 were studied and discussed in detail. The influence of critical technological parameters including pH of the feed solution, added modifier, diluent, and contact time were examined and analyzed systematically. The experiments reveal a high extraction power for Cr (IV) using Aliquat 336 in the presence of TBP, realizing no extraction of V(V) under optimized condition. Stripping of Cr(VI) from the loaded organic phase was furthermore evaluated. The present work highlights a new approach to separate Cr(VI) from strong alkaline solution with a high degree of selectivity which enables the achievement of a high purity sodium vanadate