Metastable Phase Equilibrium Of Quaternary System Li～+, Na～+, Mg～(2+)//Cl～--H₂O And Ternary System Na～+(K～+), Mg～(2+)//Cl～--H₂O At 35℃

It is famous for high composition containing boron and lithium in brines of saltlakes in Qinghai-Xizang Plateau of China. The brine systems mainly belong toLi⁺,Na⁺,K⁺,Mg²⁺(Ca²⁺)//Cl^-,CO₃^2-(HCO₃^-),SO₄^2-,borate-H₂O. It is normally called assalt-lake-brine-system for its different characters with the typical sea-water-system. Todemonstrate the recta-stable solution chemistry in the fields are essential for both intheory and multi-proposed utilization. Based on the financial supported from "AHundred Talent Program" of Chinese Academy of Sciences (0560051057) to mysupervisor, the metastable phase equilibrium and main physico-chemical properties ofthe ternary system Na⁺(K⁺),Mg²⁺//Cl^--H₂O and the quaternary system Li⁺,Na⁺,Mg²⁺//Cl^--H₂O at 35℃are studied using isothermal evaporation method.The main contents in the thesis are summarized as: solubilities and physico-chemical properties in all studied systems were determined. Based on the experimentaldata, the metastable dried salt diagram and water phase diagram in the quaternarysystem and metastable phase diagrams in the 2 ternery systems as well as the diagramsof physico-chemical properties via composition in all studied systems were plotted; Thepredictive solubilities of quaternary system were calculated using Pitzer's modelling.The main solutions got are as following:â‘ the interference of lithium ion can besuccessfully eliminated after adding an alternative amounts of the mixture solutions ofn-butyl alcohol and ethanol corresponding to the content of lithium ion. The relativeerror of the analytical results for magnesium is within 0.3%;â‘¡the meta-stable phaseequilibrium and main physico-chemical properties in the ternary system of Na⁺(K⁺),Mg²⁺//Cl^--H₂O at 35℃were studied with the isothermal evaporation method. In themeta-stable phase diagram, neither new complex salt nor solid solution are formed inthis ternary system, and there are two co-saturation points (wt/%):(KCl 0.45 MgCl₂35.98), (KCl 3.39 MgCl₂ 28.18). The prediction results of physico-chemical propertieswere in agreement with the experimental data essentially;â‘¢the phase equilibrium andmain physico-chemical properties in the quaternary system of Li⁺,Na⁺, Mg²⁺//Cl^--H₂Oare studied with the isothermal evaporation method at 35℃. The result shows that thereis neither new complex salt nor solid solution formed in this quaternary system. Thereare two co-saturation points, and their compostions are as in (wt/%): (LiCl 27.31 NaCl 0.30 MgCl₂ 14.57), (LiCl 40.54 NaCl 0.24 MgCl₂ 6.68). The meta-stable phenomenawere significant in areas near MgCl₂;â‘£solubilities of the stable quaternary systemLi⁺, Na⁺, Mg²⁺//Cl^--H₂O at 25℃is predicted finally.