Na+,K+,Rb+,Cs+//SO2-4-H2O体系固液相平衡热力学模拟
Thermodynamic Modeling of the Solid-Liquid Phase Equilibrium in the Na+,K+,Rb+,Cs+// SO42--H2O System 
投稿时间:2022-08-19  修订日期:2022-09-23
DOI:10.12119/j.yhyj.202204008
中文关键词:  铷铯  硫酸盐溶液  相平衡模拟  热力学模型  碱金属分离
英文关键词:Rb and Cs  Sulfate leachate  Phase equilibrium modeling  Thermodynamic model  Alkali metal separation
基金项目:
作者单位
樊燕飞 中南大学化学化工学院,湖南 长沙 410083 
庄子宇 中南大学化学化工学院,湖南 长沙 410083 
高丹丹 中国科学院青海盐湖研究所, 中国科学院盐湖资源综合高效利用重点实验室,青海 西宁 810008
青海省盐湖资源综合利用工程技术中心,青海 西宁 810008 
曾德文 中南大学化学化工学院,湖南 长沙 410083
中国科学院青海盐湖研究所, 中国科学院盐湖资源综合高效利用重点实验室,青海 西宁 810008 
李东东 中国科学院青海盐湖研究所, 中国科学院盐湖资源综合高效利用重点实验室,青海 西宁 810008
青海省盐湖资源化学重点实验室,青海 西宁 810008 
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中文摘要:
      锂云母、铯榴石等矿物的硫酸盐焙烧浸出,是从中提取锂铷铯钾等碱金属元素的重要步骤,所得硫酸盐浸出液可近似看作Li+,Na+,K+,Rb+,Cs+ // SO42--H2O六元水盐体系;其在浓缩过程呈现复杂的成盐特征,增加了各碱金属元素分离提取的难度,研究其相关水盐体系相图和相平衡性质对理解浸出液中碱金属的分离具有重要的理论指导意义。本文采用Pitzer-Simonson-Clegg超额Gibbs自由能方程和具有内在热力学一致性的CALPHAD方法,构建了Na+,K+,Rb+,Cs+//SO42--H2O五元体系的多温固液相平衡热力学模型。借助该模型:1)实现了对Na2SO4+Rb2SO4+H2O、Na2SO4+Cs2SO4+H2O和K2SO4+Cs2SO4+H2O三元体系的多温溶解度等温线的准确描述,并进一步构建了这些体系在240.15~380.15 K温度范围内的多温相图;2)实现了对K2SO4+Rb2SO4+H2O和Rb2SO4+Cs2SO4+H2O体系中存在的固溶体相—水溶液平衡关系的准确描述,确认了(K,Rb)2SO4连续固溶体、以及(Rb,Cs)2SO4(α)和(Rb,Cs)2SO4(β)间断固溶体存在的合理性;3)预测了上述五元体系中所包含的全部4个四元子体系(Na2SO4+ K2SO4+ Rb2SO4+H2O、Na2SO4 + K2SO4+Cs2SO4+ H2O、Na2SO4+ Rb2SO4+Cs2SO4 + H2O和K2SO4+Rb2SO4+Cs2SO4+ H2O)的相图,明确了四元相图中固溶体的类型及形成区域。然而,模型预测结果与现有四元体系实验数据间存在普遍的不一致性,尤其是固溶体形成区域,但模型预测结果从非实验角度给出了重要参考,对现有实验提出了挑战,未来对这些体系开展更为精细的实验研究非常必要。
英文摘要:
      Sulfate roasting-leaching of the mineral paragenesis of lithium,rubidium and cesium,e.g.lepidolite and pollucite,is an important step for the extraction of rare alkali metal elements such as lithium,rubidium,cesium and potassium. However,the complex salt-forming behavior of the leachate during concentrating makes it difficult to separate these alkali metal elements. The leachate can be seen as a six-component water-salt system,i.e. Li+,Na+,K+,Rb+,Cs+//SO42--H2O. Accordingly,a central scientific problem is to well understand the salt-aqueous equilibrium relation in the system. In this study,Pitzer-Simonson-Clegg excess Gibbs free energy equations and the CALPHAD method are adopted to develop a temperature-dependent solid-aqueous equilibrium model for the Na+,K+,Rb+,Cs+//SO42--H2O quinary system. Using the model,firstly,the solubility isotherms of the Na2SO4+Rb2SO4+ H2O,Na2SO4+Cs2SO4+H2O and K2SO4+Cs2SO4+H2O ternary systems are accurately represented at various temperatures,and the polythermal phase diagrams of these systems are constructed for the temperature range of 240.15 K to 380.15 K. Secondly,the solid solution-aqueous solution equilibrium in the K2SO4+Rb2SO4+H2O and Rb2SO4+Cs2SO4+H2O systems are also well represented,and the existence of a continuous solid solution (K,Rb)2SO4 and discontinuous solid solutions (Rb,Cs)2SO4(α) and (Rb,Cs)2SO4(β) are recognized. Finally,the phase diagrams of all the four quaternary sub-systems included in the above mentioned quinary system,i.e.,Na2SO4+K2SO4+Rb2SO4+H2O,Na2SO4+K2SO4+Cs2SO4+H2O,Na2SO4+Rb2SO4 +Cs2SO4+H2O and K2SO4+Rb2SO4+Cs2SO4+H2O,are predicted with the salt-formation regions of solid solution phases. However,some significant inconsistency between model prediction and the available experimental data,especially for the regions where solid solutions form,still noticeable. Nonetheless,the model predictions provide important references for understanding the solid-aqueous equilibrium in these systems,but more elaborate experiments are still necessary.
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