298 K四元体系LiCl-MgCl2-CaCl2-H2O相平衡实验及溶解度计算

采用等温溶解平衡法测定了四元体系LiCl-MgCl₂-CaCl₂-H₂O在298 K下的溶解度，由此绘制了相应的相图和水含量图。实验结果表明，该体系在298 K时有三种复盐生成，无固溶体生成。其相图中含有五个共饱点，十一条单变量曲线以及七个平衡固相结晶区，分别为四个单盐结晶区（CaCl₂·6H₂O、CaCl₂·4H₂O、MgCl₂·6H₂O和LiCl·H₂O）以及三个复盐结晶区（LiCl·MgCl₂·7H₂O、LiCl·CaCl₂·5H₂O和2MgCl₂·CaCl₂·12H₂O）。运用Pitzer模型，采用文献中报道的参数对该四元体系进行了298 K条件下的溶解度计算。对比发现，计算结果与实验数据基本吻合。

Measurements and calculations of solid-liquid equilibria in quaternary system LiCl-MgCl2-CaCl2-H2O at 298 K

Solid-liquid equilibria in the quaternary system LiCl-MgCl₂-CaCl₂-H₂O at 298 K were studied by the method of isothermal solution saturation method. Using the experimental data, the phase diagram and the relevant water diagram of the quaternary system were obtained. The results show that the phase diagram of the quaternary system consists of seven crystallization fields, eleven univariant curves, and five invariant points. In addition to four simple salts CaCl₂·6H₂O, CaCl₂·4H₂O, MgCl₂·6H₂O and LiCl·H₂O, the three double salts LiCl·MgCl₂·7H₂O, LiCl·CaCl₂·5H₂O and 2MgCl₂·CaCl₂·12H₂O also crystallizes from the saturated solutions. The crystallized area of single salt MgCl₂·6H₂O is the largest because of its smallest solubility. The solubility of the quaternary system at 298 K was calculated by Pitzer model using the parameters reported in the literature. The calculated results are basically consistent with the experimental data.