Phase behavior of aqueous Na-K-Mg-Ca-Cl-NO3 mixtures : Isopiestic measurements and thermodynamic modeling

• Published in: Journal of solution chemistry Vol. 36; no. 6; pp. 723 - 765
• Main Authors: GRUSZKIEWICZ, Mirostaw S, PALMER, Donald A, SPRINGER, Ronald D, PEIMING WANG, ANDERKO, Andrzej
• Format: Journal Article
• Language: English
• Published: New York, NY Springer 01-06-2007; Springer Nature B.V
• Subjects: ACCURACY; Calcium ions; Chemical precipitation; Chemistry; DILUTION; ELECTROLYTES; Exact sciences and technology; Freezing; General and physical chemistry; Hygroscopicity; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; Magnesium; MELTING POINTS; MIXTURES; MOLTEN SALTS; ORNL; PRECIPITATION; Research facilities; Saline solutions; SIMULATION; Sodium; Solid phases; Solutions; Subsystems; THERMODYNAMIC MODEL; Thermodynamic models; THERMODYNAMIC PROPERTIES; THERMODYNAMICS; WATER; Mixed brines; Thermodynamics; Thermodynamic model; Fused salt; Brine; Activity coefficient; Isopiestic measurements; Thermodynamic properties; Osmotic coefficient; Deliquescence; Modeling
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-007-9145-2

A comprehensive model has been established for calculating thermodynamic properties of multicomponent aqueous systems containing the Na+, K+, Mg2+, Ca2+, Cl− and NO3− ions. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300 °C and concentrations ranging from infinite dilution to the fused salt limit. The model has been parameterized using a combination of an extensive literature database and new isopiestic measurements for thirteen salt mixtures at 140 °C. The measurements have been performed using Oak Ridge National Laboratory’s (ORNL) previously designed gravimetric isopiestic apparatus, which can also detect solid phase precipitation. In addition to various Na–K–Mg–Ca–Cl–NO3 systems, results are reported for LiCl solutions. Water activities are reported for mixtures with a fixed ratio of salts as a function of the total apparent salt mole fraction. The isopiestic measurements reported here simultaneously reflect two fundamental properties of the system, i.e., the activity of water as a function of solution concentration and the occurrence of solid–liquid transitions. The thermodynamic model accurately reproduces the new isopiestic data as well as literature data for binary, ternary and higher-order subsystems. Because of its high accuracy in calculating vapor–liquid and solid–liquid equilibria, the model is suitable for studying deliquescence behavior of multicomponent salt systems.