A clean technology to separate and recover vanadium and chromium from chromate solutions

摘要

In this work, a clean technology is introduced to separate and recover vanadium and chromium from vanadium containing chromate solution. It was found that vanadium can be precipitated from vanadium-containing chromate solution by hydrolysis. The hydrolysate is the mixture of polyvanadic acid and sodium polyvanadate. The concentration of V in the solution can be decreased to 0.76 g/L under pH 2.0 at 95 degrees C. The Na in the mixture can be effectively removed by washing with (NH4)(2)SO4 solution as the bind of NH4-VO3 is stronger than that of Na-VO3. The V2O3 with purity 98.6% was acquired by calcining the washed mixture. The vanadium residue in precipitated solution can be completely removed by adding Fe2+ or Fe3+ to form iron vanadate under pH 3.8-4.5. The chromium in the V free solution was reduced from Cr(VI) to Cr(III) with Na2SO3, and then the precipitate of Cr2O3 center dot xH(2)O was formed under pH above 8.5 at 90 degrees C. At last, the Cr2O3 with purity 98.7% was obtained by the treatment of the chromic oxide hydrate. Using the process above, the generation of V-Cr-bearing reducing slag and the mixture of Na2SO4 and (NH4)(2)SO4 can be avoided in vanadium pentoxide production from vanadium-containing chromate solution.