Stable Phase Equilibrium of the Aqueous Quaternary System (MgCl2 + MgSO4 + MgB6O10 + H2O) at 323.15 K

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• 作者：Lingzong Meng ; Dan Li ; Yafei Guo ; Tianlong Deng
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2011
• 出版时间：December 8, 2011
• 年：2011
• 卷：56
• 期：12
• 页码：5060-5065
• 全文大小：794K
• 年卷期：v.56,no.12(December 8, 2011)
• ISSN：1520-5134

文摘

The solubilities and relevant physicochemical properties including density and pH values of the aqueous quaternary system (MgCl₂ + MgSO₄ + MgB₆O₁₀ + H₂O) at 323.15 K were determined for the first time with the method of isothermal dissolution. According to the experimental results, the dry-salt-phase diagram, water-phase diagram, and physicochemical properties versus composition diagrams were plotted. It was found that there are three three-salt cosaturated invariant points, seven univariant solubility isotherm curves, and five stable crystallization fields corresponding to bischofite (MgCl₂路6H₂O, Bis), kieserite (MgSO₄路H₂O, Kie), tetrahydrite (MgSO₄路4H₂O, Tet), hexahydrite (MgSO₄路6H₂O, Hex), and mcallisterite (Mg(B₆O₇)(OH)₆路4.5H₂O, Mca). Neither solid solution nor double salts were found. On the basis of the extended Harvie鈥揥eare (HW) model and its temperature-dependent equation, single-salt parameters 尾⁽⁰⁾, 尾⁽¹⁾, 尾⁽²⁾, and C for MgCl₂, MgSO₄, and Mg(B₆O₇)(OH)₆, mixed ion-interaction parameters 胃_C1,SO4, 胃_{C1,B6O7聽(OH)6}, 胃_{SO4,B6O7(OH)6}, 唯_Mg,Cl,SO4, 唯_{Mg,Cl,B6O7(OH)6}, and 唯_{Mg,SO4,B6O7(OH)6}, and the Debye鈥揌眉ckel parameter A at 323.15 K were obtained. In addition, the average equilibrium constants of stable equilibrium solids at 323.15 K were obtained with the method of the activity product constant. The prediction of solubilities of the quaternary system is then demonstrated. A comparison between the calculated and the experimental results shows that the predicted solubilities agree well with experimental data.