Vanadium, calcium, iron vanadate salt precipitation method is mainly used in low concentration of vanadium from vanadium recovery solution.
1. Calcium vanadate method
CaCl 2 , Ca(OH) 2 , CaO were added, and different precipitates were formed as the pH of the solution changed.
pH value | 10.8~11 | 7.8 to 9.3 | 5.1 to 6.1 |
Precipitate | Calcium orthovanadate | Calcium vanadate | Metavanadic acid |
Ca 3 (VO 4 ) 2 | CaV 2 O 7 | Ca(VO 3 ) 2 | |
Solubility | small | small | Slightly larger |
Gradually add vanadium intensively under strong agitation, add Ca 2 + 
The impurities will also enter the precipitate, and the silica gel will also be mixed into the precipitate. The most economical and effective precipitation of calcium pyrovadate, the vanadium precipitation rate is generally 97% to 99.5%.
Second, iron vanadate precipitation method
The iron salt or the ferrous salt is used as a precipitating agent, and the vanadium-containing solution is poured into the ferrous sulfate solution under weakly acidic conditions, and continuously stirred and heated to precipitate a green precipitate. Since the divalent iron is partially oxidized to ferric iron, V 2 O 5 is partially reduced to V 2 O 4 , so the composition of the precipitate is variable, including Fe(VO 3 ) 2 , Fe(VO 3 ) 3 , VO. 2 · xH 2 O, Fe(OH) 3 and the like. If FeCl 3 or Fe 2 (SO 4 ) 3 is used as the precipitant, a yellow xFe 2 O 3 ·yV 2 O 5 ·zH 2 O precipitate is precipitated. The precipitation rate of vanadium in this method can reach 99% to 100%.
Both iron vanadate and calcium vanadate can be used as raw materials for smelting vanadium iron or as a raw material for further purification of V 2 O 5 .
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