Measurement and Prediction of Phase Equilibria of Quaternary System LiCl–KCl–SrCl2–H2O at 273.2 K and its Applications

The underground brines in the Sichuan Basin of China are rich in lithium, potassium, strontium, chlorine, etc. In order to fully develop and utilize these brine resources, it is necessary to carry out phase equilibrium research about the quaternary system LiCl–KCl–SrCl₂–H₂O and develop a reasonable lithium extraction process. The quaternary system LiCl–KCl–SrCl₂–H₂O at 273.2 K were determined using the isothermal dissolution equilibrium method. As a result, the corresponding phase diagrams were drawn based on the data. The phase diagram shows that the quaternary system LiCl–KCl–SrCl₂–H₂O has no double salt or solid solution at 273.2 K and there are two invariant points, five univariate curves and four solid phase crystallization fields, which are LiCl·2H₂O, SrCl₂·2H₂O, SrCl₂·6H₂O and KCl. Furthermore, Pitzer’s model was used to predict the solubility of salts in the quaternary system. The calculated values are in good agreement with the experimental ones. Finally, combined with isothermal evaporation method and the phase diagram of the quaternary system, a brine evaporation process was designed.