Abstract The solid-liquid phase equilibria of the solution in the quaternary system Na+ //Cl−, SO42−, CO32−-H2O and its subsystems Na+ //Cl−, CO32−-H2O and Na+ //SO42−, CO32−-H2O at 353.15 K were measured by isothermal solution saturation method. The equilibrium solids were determined by the Schreinemaker's method of wet residues and X-ray diffraction (XRD). Based on the experimental data, the phase diagrams were plotted and analysed. There is one monohydrate in the ternary system Na+ //CO32−, Cl−-H2O at T = 353.15 K, and the phase diagram contains one invariant point, two univariant curves and four crystallization regions. The ternary system Na+ //SO42−, CO32−−H2O at T = 353.15 K is more complex than the previous system since one monohydrate and one anhydrous double salt are found; the phase diagram contains two invariant points, three univariant curves and six crystallization regions. The phase diagram of the quaternary system Na+ //Cl−, SO42−, CO32−-H2O at 353.15 K includes two invariant points, five univariant curves, and four crystallization fields of single salts corresponding to NaCl, Na2SO4, Na2CO2·H2O and 2Na2SO4·Na2CO2. The results obtained in this study can help identify the solutions from which fractional crystallization of Na2SO4 and NaCl will be more effective.

中文翻译：

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四元系统 Na+ //Cl−, SO42-, CO32−-H2O 及其子系统 Na+ //Cl−, CO32−-H2O 和 Na+ //SO42-, CO32−-H2O 在 353.15 K 的固液稳定相平衡

摘要 四元体系中溶液的固液相平衡 Na+ //Cl−, SO42−, CO32−-H2O 及其子系统 Na+ //Cl−, CO32−-H2O 和 Na+ //SO42−, CO32−-通过等温溶液饱和法测量 353.15 K 的 H2O。通过湿残留物的 Schreinemaker 方法和 X 射线衍射 (XRD) 确定平衡固体。根据实验数据，绘制和分析相图。在 T = 353.15 K 的三元体系 Na+//CO32-、Cl--H2O 中有一个一水合物，相图包含一个不变点、两条单变曲线和四个结晶区。T = 353.15 K 的三元系统 Na+ //SO42-, CO32--H2O 比之前的系统更复杂，因为发现了一种一水合物和一种无水复盐；相图包含两个不变点，三个单变量曲线和六个结晶区域。四元体系Na+//Cl-, SO42-, CO32--H2O 在353.15 K 的相图包括两个不变点、五个单变曲线和四个对应于NaCl、Na2SO4、Na2CO2·H2O 和2Na2SO4 的单盐结晶场·Na2CO2。本研究中获得的结果有助于确定 Na2SO4 和 NaCl 分步结晶更有效的溶液。