Phase Equilibria and Phase Diagrams for the Aqueous Ternary System (Na2SO4 + Li2SO4 + H2O) at (288 and 308) K

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• 作者：Yafei Guo ; Yuanhui Liu ; Qin Wang ; Chenxiao Lin ; Shiqiang Wang ; Tianlong Deng
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2013
• 出版时间：October 10, 2013
• 年：2013
• 卷：58
• 期：10
• 页码：2763-2767
• 全文大小：289K
• 年卷期：v.58,no.10(October 10, 2013)
• ISSN：1520-5134

文摘

The solubility and density of the thermodynamic phase equilibria ternary system (Na₂SO₄ + Li₂SO₄ + H₂O) at (288 and 308) K were determined using the isothermal dissolution method. According to the experimental results of the ternary system at (288 and 308) K, the phase diagrams and the diagrams of density versus composition were plotted. In the ternary system at 308 K, four crystallization regions corresponding to thenardite (Na₂SO₄, Th), two congruent double salts of Li₂SO₄路3Na₂SO₄路12H₂O (Db1) and Li₂SO₄路Na₂SO₄ (Db2), and lithium sulfate monohydrate (Li₂SO₄路H₂O, Ls) were found, whereas only three crystallization regions corresponding to Ls, one incongruent double salt of Db1, and mirabilite (Na₂SO₄路10H₂O, Mir) were found in the system at 288 K. No solid solution was found at either temperature. When the experimental phase diagram at 308 K was compared with that at 288 K, it shows that (1) a new phase region of double salt Db2 was formed and the mineral of Mir transformed into Th with the increase of temperature from (288 to 308) K and (2) the area of the crystallization region of sodium sulfate was decreased sharply and those of the crystallized regions of Li₂SO₄路H₂O and double salt Db1 increased obviously. The solution densities of the ternary system both at (288 and 308) K change regularly with increasing lithium sulfate concentration in solution. Based on the Pitzer model and its extended Harvie-Weare (HW) model, the mixing triple interaction parameter of 唯_Li,Na,SO4 at (288 and 308) K and the solubility equilibrium constants K_sp of solid phases Ls, Db1, Db2, Th, and Mir at (288 and 308) K, which are not reported in the literature, were acquired by fitting the experimental solubility data of the ternary system (Li₂SO₄ + Na₂SO₄ + H₂O) by the lease-square method. A comparison between the calculated and experimental results at (288 and 308) K for the ternary system shows that the predicted solubilities obtained with the extended HW model agree well with experimental data.