Simulation and prediction of solubility phase diagram for the separation of MgCl2 from LiCl brine using HCl as a salting-out agent

The phase equilibrium of the HCl–LiCl–MgCl2–H2O system was simulated over a wide range of temperature and concentration by using an extended BET model. The experimental solubility and water activity in the binary HCl–H2O, LiCl–H2O, MgCl2–H2O and ternary HCl–LiCl–H2O, HCl–MgCl2–H2O and LiCl–MgCl2–H2O systems were used to obtain the model parameters. Then the solubility isotherms in the quaternary HCl–LiCl–MgCl2–H2O system were predicted and compared with the available experimental data. It was shown that the extended BET model with few model parameters can perfectly predict the solubility of the highly soluble quaternary HCl–LiCl–MgCl2–H2O system over a wide temperature range from 273 K to 413 K. The predicted phase diagram proved to be trustworthy and reliable for the industrial process design of separating MgCl2 from LiCl-containing natural brine using HCl as a salting-out agent.