Comprehensive thermodynamic modeling of saline water with electrolyte NRTL model: A study of aqueous Sr2+-Na+-Cl−-SO42− quaternary system

This study reports the parameters of electrolyte nonrandom two-liquid (eNRTL) model for aqueous Sr2+-Na+-Cl--SO42- quaternary system. The molecule-electrolyte interaction parameters of eNRTL model and their temperature coefficients are identified for the H2O:(Sr2+-Cl-) pair via regression of available experimental data including vapor pressure, mean ionic activity coefficient, osmotic coefficient, liquid molar enthalpy, and liquid molar heat capacity. The electrolyte-electrolyte interaction parameters and their temperature coefficients are determined for the (Sr2+-Cl-):(Na+-Cl-) pair via regression of available solubility data of SrCl2 and SrSO4 in aqueous NaCl solution. Due to the low solubility of SrSO4 in water, the eNRTL interaction parameters corresponding to the Debye-Hückel theory are chosen for the H2O:(Sr2+-SO42-) pair and the interaction parameters for the (Sr2+-SO42-):(Na+-SO42-) and (Sr2+-Cl-):(Sr2+-SO42-) pairs are set to zero. The interaction parameters for the remaining molecule-electrolyte pairs, H2O:(Na+-Cl-) and H2O:(Na+-SO42-), and the electrolyte-electrolyte pair, (Na+-Cl-):(Na+-SO42-), are directly retrieved from the literature. The resulting eNRTL model satisfactorily calculates all thermodynamic and calorimetric properties for the quaternary system at 273.15-523.15 K and salt concentrations up to saturation.