Stable Phase Equilibrium in the Aqueous Quaternary System Rb+, Mg2+//Cl–, borate–H2O at 323 K

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• 作者：Ying Zeng ; Gang Xie ; Chun Wang ; Xudong Yu
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2016
• 出版时间：July 14, 2016
• 年：2016
• 卷：61
• 期：7
• 页码：2419-2425
• 全文大小：380K
• 年卷期：0
• ISSN：1520-5134

文摘

The quaternary water–salt system Rb⁺, Mg²⁺//Cl^–, borate–H₂O is an important subsystem of the composition of Pingluo underground brine, Sichuan province. An isothermal dissolution equilibrium method was used to study the phase equilibrium of the system, and the solubilities, densities, and refractive indices of the equilibrated solution of the system were determined. On the basis of the solubility data, the isothermal dissolution phase diagram, the water figure, the diagrams for the density-composition and refractive index-composition were obtained. Results suggest that the quaternary system is of a complex reciprocal system with the formation of double salt RbCl·MgCl₂·6H₂O. Three invariant points and seven univariant curves divide the phase diagram into five crystalline zones. The five crystalline regions correspond to four single salts, rubidium chloride (RbCl), bischofite (MgCl₂·6H₂O), rubidium pentaborate tetrahydrate (RbB₅O₆(OH)₄·2H₂O), and hungchaoite (MgB₄O₅(OH)₄·7H₂O), and one double salt rubidium-carnallite (RbCl·MgCl₂·6H₂O). The size of the RbB₅O₆(OH)₄·2H₂O crystallization field is the largest, whereas that of MgCl₂·6H₂O is the smallest. Comparisons between the stable phase diagrams at 323 K and 348 K show that there is no change with the crystallization forms of the salts, while the crystallization field of salt RbB₅O₆(OH)₄·2H₂O becomes obviously larger with the increase of temperature; a rise in temperature is beneficial to separate RbB₅O₆(OH)₄·2H₂O from the solution.