Cyclic metallurgical process for extracting V and Cr from vanadium slag: Part II. Separation and recovery of Cr from vanadium precipitated solution

Abstract

Cyclic metallurgical process for separation and recovery of Cr from vanadium precipitated solution by precipitation with PbCO3 and leaching with Na2CO3 was investigated. The concentration of Cr residue in the solution decreases from 2.360 to 0.001 g/L by adding PbCO3 into vanadium precipitated solution according to Pb/Cr molar ratio of 2.5, adjusting the pH to 3.0 and stirring for 180 min at 30 °C. Then, the precipitates were leached with hot Na2CO3 solution to obtain leaching solution containing Na2CrO4 and leaching residue containing PbCO3. The leaching efficiency of Cr reaches 96.43% by adding the precipitates into 0.5 mol/L Na2CO3 solution with the mass ratio of liquid to solid (L/S) of 10:1 mL/g and stirring for 60 min under pH 9.5 at 70 °C. After filtration, leaching residue is reused in Cr precipitation and leaching solution is used to circularly leach the Cr precipitates until Na2CrO4 approaches the saturation. Finally, the product of Na2CrO4·4H2O is obtained by evaporation and crystallization of leaching solution.