Phase Equilibria Of Systems Containing Lithium,Sodium,Potassium,Calcium,Strontium And Chloride

The western region of China has a large amount of underground brine and oilfield brine resources,especially the oilfield brine in the South Wingshan area of the Qaidam Basin,which is rich in lithium,potassium,ammonia,strontium and other resources.The important theoretical basis of separation and extraction,so carrying out phase equilibrium research with the characteristics of the brine system of this oilfield is of great significance for the development and utilization of brine water resources in this area.In this paper,the isothermal dissolution equilibrium method is used to carry out phase equilibrium studies of some quaternary systems and ternary subsystems in systems containing lithium,sodium,potassium,calcium,and strontium,including four ternary systems:Li Cl-Sr Cl₂-H₂O(308K,323K),NH₄Cl-Na Cl-H₂O(308K),Ca Cl₂-NH₄Cl-H₂O(288K,308K),NH₄HB₄O₇-NH₄Cl-H₂O(288K,308K,323K,348K);three quaternary systems:Sr Cl₂-NH₄Cl-Na Cl-H₂O(308K),Sr Cl₂-KCl-Li Cl-H₂O(308K,323K)and Sr Cl₂-Na Cl-Li Cl-H₂O(308K).Based on the measured experimental data,phase diagrams of the ternary system and the quaternary system were drawn.The phase diagrams of the ternary system Li Cl–Sr Cl₂–H₂O at 288K,308K and 323K were compared.There was no double salt or solid solution formation at these three temperatures.The system has two invariable points,three invariable curves and three Single salt crystallization regions.The phase diagrams has two invariable points and the solid phase compositions are Sr Cl₂·6H₂O+Sr Cl₂·2H₂O,Sr Cl₂·2H₂O+Li Cl·2H₂O at 288K.The phase diagrams has two invariable points and the solid phase composition are Sr Cl₂·6H₂O+Sr Cl₂·2H₂O,Sr Cl₂·2H₂O+Li Cl·H₂O at 308K and 323K.The phase diagrams of the ternary system NH₄Cl-Na Cl-H₂O is a complex ternary system with solid solution formation at 308K.The phase diagrams of the ternary system NH₄HB₄O₇–NH₄Cl–H₂O at 288K,308K,323K and 348K were compared.At these four temperatures,no double salt and solid solution were formed.It belongs to a simple saturated system.The system has one invariable point,2 invariable curves and 2 Single salt crystallization regions.The phase diagrams of the ternary system Ca Cl₂-NH₄Cl-H₂O were compared at 288K and 308K.There was no double salt or solid solution formation at 288K and 308K.It belongs to a simple saturated system.The system has one invariable point,two invariable Curves and two Single salt crystallization regions.The crystallization area of NH₄Cl in the system increases with increasing temperature,while the crystallization area of Ca Cl₂·6H₂O hydrate becomes smaller.The phase diagrams of the quaternary system Sr Cl₂-KCl-Li Cl-H₂O were compared at288K,308K and 323K.No double salt and solid solution were formed.There were only two invariable points,four single salt crystallization regions and 5 five invariable curves at these three temperatures.Six strontium chlorides(Sr Cl₂·6H₂O)in the crystal water will gradually dehydrate in the crystallization process to become strontium chlorides(Sr Cl₂·2H₂O)in the two crystal waters due to the action of lithium chloride.The phase diagrams of the quaternary system Sr Cl₂-NH₄Cl-Na Cl-H₂O is a complex ternary system with solid solution formation.The phase diagrams of the quaternary system Sr Cl₂-Na Cl-Li Cl-H₂O has no double salt and solid solution formation at 308K.It is a simple saturated system.