Solubility Phase Diagram of the Ternary System MgCl₂–MgSO₄–H₂O at 323.15 and 348.15 K

Abstract

Utilizing improvements in experimental equipment, analytical methods and the initial material, the solubility isotherms of the ternary system MgCl 2 −MgSO 4 −H 2 O were determined in detail at T = (323.15 and 348.15) K using an isothermal method of solid−liquid equilibrium. The results indicate that the solid phases MgSO 4 •nH 2 O (s) (n = 6, 1) and MgCl 2 •6H 2 O (s) are stable and MgSO 4 •nH 2 O (s) (n = 5, 4) are metastable at 323.15 K, which contradicts the results of a previous experimental study 1 in which the phase MgSO 4 •4H 2 O (s) was reported as stable. The liquidus of the four solid phases MgSO 4 •nH 2 O (s) (n = 6, 4, 1) and MgCl 2 •6H 2 O (s) were measured at 348.15 K in this work. The findings indicate that the phases MgSO 4 •H 2 O (s) and MgCl 2 • 6H 2 O (s) are stable and MgSO 4 •6H 2 O (s) and MgSO 4 •4H 2 O (s) are metastable at 348.15 K. Remarkable differences between this work and the literature solubility data for the phase MgSO 4 •H 2 O (s) at 348.15 K are observed. A Pitzer−Simonson−Clegg thermodynamic model was chosen to simulate the properties of the binary systems and to correlate the solubility isotherms of the ternary system at 298.15 K in our previous study and 323.15 K and 348.15 K in this work. Good agreement has been found between the calculated and experimental results. Applying the model parameters and solubility isotherms in the ternary system measured in this work, we obtained the solubility product parameters ln K and chemical potentials for the solid phases MgSO 4 •nH 2 O (s) (n = 6, 5, 4, 1) over a wider temperature range than those for the binary system MgSO 4 −H 2 O.

Solubility Data of Potential Salts in the MgO-CaO-SO2-H2O-O2 System for Process Modeling

“…pentahydrate, may coexist in this temperature range [16][17][18] and different studies give partially contradictory new insides in the complicated reaction system [18].…”

“…Many studies have examined the stability of different hydrate forms of MgSO 4 [16][17][18][19][20]. Following the study by Li et [17].…”

Thermodynamic Properties of LiCl + MgSO4 + H2O at Temperatures from 273.15 K to 373.15 K and Representation with Pitzer Ion-Interaction Model

“…The thermodynamic properties of the binary subsystems of LiCl + H 2 16 have been reported. The thermodynamic properties and phase diagrams predicted by using the Pitzer ion interaction model for some seawater systems at various temperatures, 9,17 as well as for salt lake brine systems containing lithium at 298.15 K, have also been reported.…”

“…The thermodynamic properties of the binary subsystems of LiCl + H 2 O, MgCl 2 + H 2 O, Li 2 SO 4 + H 2 O, and MgSO 4 + H 2 O have been extensively studied, and their models are available over a wide range of molality and temperature. 1−9 The ternary subsystems with a common ion like LiCl + MgCl 15 and 348.15) K 16 have been reported. The thermodynamic properties and phase diagrams predicted by using the Pitzer ion interaction model for some seawater systems at various temperatures, 9,17 as well as for salt lake brine systems containing lithium at 298.15 K, have also been reported.…”

“…LiCl + MgSO 4 + H 2 O is a subsystem of the quaternary reciprocal system of Li + + Mg 2+ + Cl – + SO 4 2– + H 2 O, which occurs in many salt lake brines and ground brines of oil field and is important to the utilization of brine resources. The thermodynamic properties of the binary subsystems of LiCl + H 2 O, MgCl 2 + H 2 O, Li 2 SO 4 + H 2 O, and MgSO 4 + H 2 O have been extensively studied, and their models are available over a wide range of molality and temperature. − The ternary subsystems with a common ion like LiCl + MgCl 2 + H 2 O, Li 2 SO 4 + MgSO 4 + H 2 O, LiCl + Li 2 SO 4 + H 2 O, and MgCl 2 + MgSO 4 + H 2 O at T = 298.15 K have been measured. − Experimental redetermination and model simulation of the solubility phase diagram for the quaternary system of Li + , Mg 2+ //Cl – , SO 4 2– –H 2 O at 298.15 K and 323.15 K and the solubility phase diagram of the ternary system of MgCl 2 –MgSO 4 –H 2 O at (323.15 and 348.15) K have been reported. The thermodynamic properties and phase diagrams predicted by using the Pitzer ion interaction model for some seawater systems at various temperatures, , as well as for salt lake brine systems containing lithium at 298.15 K, have also been reported. − However, the studies for the salt lake brine system and its ternary subsystems containing lithium at a wide range of temperatures are lacking.…”