Study on the Phase Equilibria of the Ternary Mixed Solvent System NaCl–NaBr–CH3OH–H2O at 298 and 323 K

Abstract

Aiming to improve the utilization of bromine resources in bittern, the solubilities of the ternary NaCl–NaBr–CH3OH–H2O mixed solvent system at 298 and 323 K were measured by the method of isothermal dissolution equilibrium, and the corresponding phase diagrams were constructed. The results show that the phase diagrams at the two temperatures are similar, and both have only one univariant curve and one crystallization region corresponding to a solid solution Na(Cl, Br) without invariant points. Based on the extended Pitzer model, Pitzer parameters were calculated, and the activity product of the solid solution was regressed into a polynomial of Br– mole fraction in the solid solution. The solubilities of the ternary NaCl–NaBr–CH3OH–H2O mixed solvent system at 298 K were calculated. The computed results are in accordance with the experimental values.