碱（土）金属氯化物八元体系（25-75）℃相平衡及光卤石型复盐热力学研究

The underground brine, which characterized as high concentration with potassium, sodium, boron, lithium, rubidium, and cesium, possess great development value. When the underground brine evaporated to the old brine stage，the main contents of the brine can be described as the alkalis(alkaline earth)-chloride type complex system Li+Rb+Na+K+Cs+Ca+Mg+Cl+H2O. In the above mentioned aqueous system, the alkalis, alkaline earth and chloride can form various hydrated salts, solid solution, and double salt, which increase the difficulty of the separation and extraction technique. It is well known that phase diagram is the basis and guidance of utilization of liquid mineral resources and separation techniques of salts. Therefore, the metastable phase equilibria on the aqueous chlorides system containing lithium, potassium, rubidium, and cesium at multi-temperature are essential. To the best of our knowledge, research aimed at the component characteristics of the old underground brine has not been reported in the literature yet. Accordingly, the measurements of the metastable phase equilibrium of the eight - component system are new development about phase equilibrium research. By means of the isothermal evaporation method, the metastable phase equilibrium on the eight - component system at 25-75℃ and the solubilities of the chloride salt(lithium, potassium, rubidium, magnesium, and cesium) at different temperature will be investigated, the metastable phase diagram can be constructed based on the measured data. According to the phase diagram, the crystallized fields of the salts and the law of precipitation of salts can be obtained. Meanwhile, the research about the thermodynamics of the carnallite double salts, such as the formulation condition, spectroscopy characterization, crystalline structure, and solubility idiosyncrasy, will be done. Through the above research, the thermodynamic basis data will be more plentiful and can be give guidance about the trace elements extraction process.

地下卤水以富钾、钠、硼、锂、铷、铯为特征，极具开发价值。地下卤水蒸发至老卤阶段，其主要组分可归属于以碱金属氯化物为主体的八元体系Li+Na+K+ Rb+Cs+Ca+Mg+Cl+H2O。因碱金属、碱土金属的氯化物间极易形成水合物、复盐或固溶体，按常规盐类提取分离技术，难以彻底分离，急需含锂钾铷铯的高元体系多温介稳相图研究成果作指导。八元体系相关系研究是相平衡研究的新开拓，表征地下卤水老卤组成特点的高元体系多温相关系研究未见报道。本课题拟开展该八元体系及子体系25 ℃-75 ℃范围内的介稳相平衡研究，测定锂钾铷铯镁的氯化物盐在不同温度下的溶解度数据，探求盐类溶解析出规律及平衡固相盐的客观存在形式，并绘制多温介稳相图；同时全面系统地研究光卤石型复盐的生成条件、光谱学特性、晶体结构及水溶解特性，丰富热力学基础数据，并指导制定卤水微量元素分离提取工艺路线。

地下卤水以富钾、钠、硼、锂、铷、铯为特征，极具开发价值。地下卤水蒸发至老卤阶段，其主要组分可归属于以碱金属氯化物为主体的八元体系Li+Na+K+Rb+Cs+Ca+Mg+Cl+H2O。本项目针对地下卤水老卤组成特点，开展了该八元体系及子体系25 ℃-75 ℃范围内的介稳相平衡研究，主要创新点及成果如下：（1）获取了大量的热力学基础数据。采用等温蒸发法，开展了该简单八元体系及其子体系25~75℃介稳相平衡研究，测定了锂钾铷铯镁的氯化物盐在不同温度下的溶解度数据，同时测定了对应体系饱和溶液的密度、折光率等物化性质，绘制了相图、水图、密度—组成图和折光率—组成图，确定了不同体系在25~75℃间的研究温度下的结晶析出形式、析盐相区等析盐规律及温度对析盐规律的影响。（2）建立了复杂高元碱金属氯化物体系相图的实验研究方法。八元体系相关系研究是相平衡研究的新开拓，不但体系组分多，且共同组分的原子结构、离子半经、晶格类型及晶格参数相近，组分间极易形成复盐或固溶体，大大增加了相图研究的复杂性。本项目在原有基础上，改进实验装置控制湿度、温度等实验条件，改进分析测试方法，并采用Schreinemarkers湿渣法、油浸法及XRD法联用鉴定平衡固相，很好地解决了固液相的快速分离、溶解度的准确测定、析盐区的准确判断、高元体系相关系图的合理表征等一系列技术问题。（3）发现了锂钠钾铷铯等碱金属氯化盐水盐体系相关系特征。研究发现，KCl和RbCl间易形成固溶体[(K, Rb)Cl]；KCl和CsCl间易形成固溶体[(K, Cs)Cl]；RbCl和CsCl间易形成固溶体[(Rb, Cs)Cl]；[(K, Rb)Cl]、[(K, Cs)Cl]、[(Rb, Cs)Cl]等三种固溶体的析出相区受温度影响较大；LiCl和NaCl间不易形成固溶体或复盐；LiCl和CsCl不易形成固溶体或复盐；LiCl和RbCl间也不易形成固溶体或复盐。（4）发现了锂钾铷铯镁共存的MeCl--MgCl2-H2O水盐体系相关系特征。锂、钾、铷、铯的氯化物盐和氯化镁间极易形成复盐，复盐形式分别为锂光卤石 (LiCl·MgCl2·7H2O)、钾光卤石(KCl·MgCl2·6H2O)、铷光卤石(RbCl·MgCl2·6H2O)和铯光卤石(CsCl·MgCl2·7H2O)；氯化钠与氯化镁盐间无复盐形成。