Measurement and thermodynamic model study on equilibrium solubility in the aqueous system of magnesium chloride and magnesium bromide

Solubilities of the ternary system MgCl2–MgBr2–H2O at T=(288.15, 308.15, 323.15 and 333.15) K were investigated, and the crystallization behaviour of solid solution Mg(Cl,Br)2·6H2O was established. Combining our experimental results with other experimental data available in the literature at T=(298.15 and 313.15) K, the pure electrolyte solution parameters for binary systems, the T-variation mixing parameters θCl,Br and ψMg,Cl,Br and the equilibrium constants equations of the solid solution were obtained. Based on Pitzer model and Harvie–Weare solubility approach, the solubility modelling approach achieved a very good agreement with chloride and bromide salts equilibrium solubility data. Temperature-dependent equation in the system provides reasonable mineral solubility at T=(288.15–333.15) K. This model expands the solubility calculation in the systems containing solid solution by evaluating chloride–bromide mixing solution parameters. Limitations of the mixed solution models due to data insufficiencies are discussed.