柴达木盆地盐湖以卤水中富含锂钾硼而闻名于世。盐田生产分卤点采用海水型五元体系相图指导，各分卤点存在明显偏离，致使锂、钾、硼在各阶段分散析出而损失严重，锂的富集成卤率仅为20～30%，导致该卤水资源的严重浪费。因此，开展富锂钾硼卤水体系相平衡与化学模型研究对合理开发该硫酸镁亚型盐湖卤水至关重要。本项目采用等温溶解平衡法开展含锂硼溶液体系Li+,Na+,K+,Mg2+//Cl-,SO42-,B4O72-—H2O及其子体系在0℃、25℃、50℃相平衡研究；采用微量热法开展含锂硼体系热容、稀释热、混合热等热力学性质研究，结合相平衡和微量热法实验研究结果，拟合所缺的含锂、硼体系Pitzer模型参数，发展Pitzer电解质溶液模型，构建该卤水体系溶解度理论计算的化学模型。研究成果为该类型宝贵盐湖资源锂钾硼产品开发及其综合利用提供重要的化工热力学基础数据；同时也会极大地丰富和发展电解质溶液理论。

Salt lake brines in Qaidam Basin are famous for their abundance of lithium and boron resources around the word. The point of brine separation in solar pond adopted the simplified phase diagrams of the seawater quinary system and the obvious deviation existed in each point of brine separation, which led to the heavy losses of potassium, lithium, and boron owing to their precipitation at each stage, and the rate of bittern of lithium is only twenty to thirty percent. It results in the serious waste of the brine resources. Therefore, it is very significant to develop the phase equilibrium and chemical model study of the brine systems containing lithium and boron for rationally exploiting and comprehensively utilizing the magnesium sulfate subtype salt lake brine resources. In this project, the novel experimental methods including the isothermal dissolution equilibrium method for stable phase diagram of the multi-systems containing lithium and boron Li+,Na+,K+,Mg2+//Cl-,SO42-,B4O72-—H2O at 0℃, 25℃, 50℃, and microcalorimetric method for the thermodynamic properties of heat capacity, heat of dilution, and heat of mixing of the binary and ternary systems containing lithium and boron will be adopted. Combined the experimental measuring results on phase equilibria and microcalorimetry, a further extends the electrolyte theory on the basis of Pitzer’s theory, and a series of the single salt parameters and the mixing-ion interaction parameters will be obtained. And then, a new predictive chemical model for the magnesium sulfate subtype of brine resources will be formed based on Pitzer model. The research results obtained in this project will provide a series of significant fundamental thermodynamic data of chemical engineering to promote the development of lithium, potassium, and boron products and to guide the comprehensive utilization of this precious salt lake brine resources, and also can enrich and develop the theory of electrolyte solution.