Measurement and correlation on stable phase equilibria of ternary system NaBr−Na2SO4−H2O at 273.2 K and 308.2 K and its application for sodium sulfate separation from underground brines

• Published in: Fluid phase equilibria Vol. 570; p. 113781
• Main Authors: Zeng, Xing-Xing, Sang, Shi-Hua, Zhang, Han-Zhong, Zhu, Kuang-Yi, Hu, Chun-Tao, Cui, Rui-Zhi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2023
• Subjects: Industrial separation; Phase equilibrium; Pitzer model; Sodium sulfate; Underground brine; Industrial separation; Pitzer model; Phase equilibrium; Sodium sulfate; Underground brine
• ISSN: 0378-3812; 1879-0224
• DOI: 10.1016/j.fluid.2023.113781

The stable phase equilibria of the ternary system NaBr−Na2SO4H2O at 273.2 K and 308.2 K were determined using the isothermal dissolution equilibrium method. The phase diagrams of the ternary system at different temperatures were plotted using the solubility of each salt in the equilibrium liquid phase, and the solid phases of invariant points in the ternary system were determined by X-ray powder diffraction. The ternary system NaBr−Na2SO4−H2O at 273.2 K has one invariant point, two univariate curves and two solid-phase crystallization regions, namely NaBr·2H2O and Na2SO4·10H2O, respectively. When the temperature rises to 308.2 K, Na2SO4·10H2O is completely dehydrated due to the effect of temperature increase, leading to the crystallization of sodium sulfate in the form of Na2SO4. The ternary system at 308.2 K has only one invariant point, two univariate curves and two solid-phase crystallization regions for NaBr·2H2O and Na2SO4, respectively. Furthermore, the solubilities of the ternary system NaBr−Na2SO4−H2O at different temperatures were predicted by using the Pitzer model. Comparing with the experimental data and phase diagram, it was found that the calculated solubility data and the experimental data were in good agreement. Finally, the separation process of sodium sulfate was designed by using the phase diagram of the ternary system, and the material balance of the separation process was established, which provides a guidance for the comprehensive utilization of the underground brines.