Determination and Analysis of Solubility of Na3VO4 in Aqueous NaOH Solutions Containing Na2CO3, NaAlO2, or Na2SiO3 at 298.15-353.15 K

In a new vanadium extracting process, the effective separation of Na3VO4 from the aqueous NaOH solution containing impurities of Na2CO3, NaAlO2, or Na2SiO3 plays a significant role. The solubility data of NaOH-Na3VO4-H2O system and NaOH-Na2CO3-Na3VO4-H2O system at 298.15, 313.15, and 353.15 K were measured. The Na3VO4 solubility in NaOH solutions containing 30.4 g.L-1 NaAlO2 or Na2SiO3 at 313.15 and 353.15 K were also studied for comparison. Na2CO3 has a strong salting-out effect on Na3VO4 with NaOH molality 10 mol.kg(-1). The determined solubility data and equilibrium solid phases are essential in optimizing the operating parameters for Na3VO4 crystallization from actual NaOH solutions. To balance the crystal purity and vanadium recovery, a strategy has been proposed for the effective separation of Na3VO4 by evaporation/cooling crystallization after decreasing the Na2CO3 concentration