为了获取铷镁、铯镁共存硫酸盐体系在273.2 K下各盐结晶的形式,文章采用等温溶解平衡法、Schreinemakers湿渣法,结合X射线粉晶衍射开展了在273.2 K下三元体系Rb+,Mg2+//SO42--H2O和Cs+,Mg2+//SO42--H2O固液相平衡研究.结果表明,两个三元体系在273.2 K时均为复杂体系,分别生成拥有较大结晶相区的复盐Rb2SO4·MgSO4·6H2O和Cs2SO4·MgSO4·6H2O,即铷镁、铯镁共存硫酸盐体系在273.2 K下铷铯不易单独析出.多温对比结果表明,三元体系Rb+,Mg2+//SO42--H2O在 273.2、298.2 和 308.2 K 时均生成 Rb2SO4·MgSO4·6H2O、Rb2SO4和MgSO4·7H2O,且复盐 Rb2SO4·MgSO4·6H2 O的结晶区均最大,单盐Rb2SO4的结晶区均最小,三个结晶区均随温度升高而增大.三元体系Cs+,Mg2+//SO42--H2O 在 273.2、298.2 和 308.2 K 均有三个结晶区(Cs2SO4·MgSO4·6H2O＞MgSO4·7H2O＞Cs2SO4),随着温度的升高,三个结晶区均略有减小.
Solid-Liquid Phase Equilibria in the Aqueous Ternary System Rb+(Cs+),Mg2+//SO42-H2O at 273.2 K
In order to determine the crystalline forms of in the rubidium-magnesium and cesium-magnesium coexisting sulfate system at 273.2 K,the isothermal dissolution method combined with Schreinemakers method and X-ray powder diffraction was used to conduct the solid-liquid phase equilibria studies of two ternary systems Rb+,Mg2+//SO42-H2O and Cs+,Mg2+//SO42-H2O at 273.2 K.The results indi-cate that these two ternary systems are both complex systems at 273.2 K,each forming a double salt with large crystallization region,namely Rb2SO4·MgSO4·6H2O and Cs2SO4·MgSO4·6H2O,which means that rubidium and cesium are not easily precipitated and separately in the coexisting sulfate system of Rb+,Mg2+//SO42-H2O and Cs+,Mg2+//SO42-H2O.Comparative results at multiple temperatures show that the ter-nary system Rb+,Mg2+//SO42-H2O at 273.2,298.2 and 308.2 K consistently forms Rb2SO4·MgSO4·6H2O,Rb2SO4 and MgSO4·7H2O.The crystallization region of the double salt Rb2SO4·MgSO4·6H2O is the larg-est,while that of salt Rb2SO4 is the smallest,with all three crystallization regions increasing as the tempera-ture rises.For the ternary system Cs+,Mg2+//SO42-H2O has three crystalline regions at 273.2,298.2 and 308.2 K(Cs2SO4·MgSO4·6H2O＞MgSO4·7H2O＞Cs2SO4),and these areas slightly decrease as the tem-perature rises.
Phase equilibriumRubidium sulfateCesium sulfateDouble salt
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