Solubility measurement and thermodynamic modeling of solid-liquid equilibria in quaternary system NaCl-CaCl2-SrCl2-H2O at 323.15 K

The solid-liquid phase equilibria in the systems NaCl-SrCl2-H2O and NaCl-CaCl2-SrCl2-H2O at 323.15 K were studied with the isothermal dissolution method. The solid-liquid equilibrium phase diagrams were constructed with the experimental results. A comparison of the diagrams of system NaCl-SrCl2-H2O from 288.15 to 373.15 K shows that area of strontium chloride salt region decreased obviously whereas the areas of NaCl almost invariant. The dry-salt diagram of the NaCl-CaCl2-SrCl2-H2O system consists of four single-salt crystallization regions for NaCl, SrCl2 center dot 6H(2)O, SrCl2 center dot 2H(2)O and CaCl2 center dot 2H(2)O, five univariant solubility curves and two invariant points. Combining Pitzer binary parameters obtained in the literatures, the Pitzer mixing parameters theta(Na,Ca), theta(Na),(Sr), theta(Ca,Sr) Psi(Na,Sr,Cl), Psi(Na,Sr,Cl) and Psi(Ca),(Sr,Cl) were fitted with the solubility data in this study and literatures. The model was then used for predicting the solubilities of the two systems. The experimental data are in accordance with the predicted results. (C) 2019 Elsevier Ltd.