Simulation studies on metastable phase equilibria in the aqueous ternary systems (NaCl-MgCl₂-H₂O) and (KCl-MgCl₂-H₂O) at 308.15 K

Abstract

The solubilities and densities of the aqueous metastable ternary systems (NaCl-MgCl₂-H₂O) and (KCl-MgCl₂-H₂O) at 308.15 K were determined by the isothermal evaporation method. On the basis of the experimental results, the phase diagrams for those systems were plotted. It was found that the former system belongs to the hydrate-I type with one invariant point of (NaCl+ MgCl₂·6H₂O), two univariant curves, and two crystallization regions corresponding to halite (NaCl) and bischofite (MgCl₂·6H₂O); and the latter system belongs to the type of incongruent-double salts with two invariant points of (KCl+ KCl·MgCl₂·6H₂O) and (MgCl₂·6H₂O+ KCl·MgCl₂·6H₂O), three univariant curves, and three crystallization regions corresponding to potassium chloride (KCl), carnallite (KCl·MgCl₂·6H₂O) and bischofite (MgCl₂·6H₂O). No solid solutions were found in both systems.

Keywords

green chemistry / solar pond technique / simulation / metastable phase equilibrium / solubility

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Acknowledgements

Financial support from the State Key Program of National Natural Science of China (No. 20836009), the National Natural Science Foundation of China (Grant Nos. 40573044, 40773045), the “A Hundred Talents Program” of the Chinese Academy of Sciences (No. 0560051057), and the Specialized Research Fund for the Doctoral Program of Chinese Higher Education (No. 20060616004) is greatly acknowledged. The authors also thank Professor Gao Z H, Sun B, and Wang P for their valuable help. Thanks also to the Editor and the anonymous reviewers for their active comments on the manuscript.

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