Journal of Chemical and Engineering Data, Vol.66, No.1, 85-93, 2021
Experimental Determination of Phase Equilibria in the Quaternary NaOH-Na3VO4-Na2MoO4-H2O System at 298.15-353.15 K
The equilibrium solubility of the quaternary NaOH-Na3VO4-Na2MoO4-H2O system was investigated from 298.15 to 353.15 K using an isothermal equilibrium method. From the results, the solubility of Na3VO4 decreased appreciably as temperature decreased. The solubility of Na3VO4 decreased sharply as the NaOH concentration increased, and the effect of temperature on the Na3VO4 solubility was not obvious. The dry-salt phase diagram of the system consists of three crystallization zones (where the solid phases are Na3VO4 center dot 12H(2)O at 298.15 K and Na3VO4 center dot 3H(2)O at 313.15-353.15 K, Na2MoO4 center dot 2H(2)O, and NaOH center dot H2O). The solubilities of Na3VO4 and Na2MoO4 were compared with those of their ternary subsystems of NaOH-Na3VO4-H2O and NaOHNa2MoO4-H2O, respectively. Na2MoO4 has a strong salting-out effect on Na3VO4 solubility when the NaOH concentration was smaller than approximately 30 wt %. The addition of Na3VO4 has almost no salting-out effect on the Na2MoO4 solubility especially when the NaOH concentration was above 20 wt %.