Study Of The Meta-stable Phase Equilibrium Of The Quarternary System Li～+, Na～+, Ca～(2+)//Cl～--H₂O And Its Three Ternary Sub-systems At 15℃

The meta-stable phase equilibrium of the quarternary system Li⁺,Na⁺,Ca²⁺//Cl -- H₂O and its three sub-systems at 15℃were studied using isothermal evaporation method in the thesis. The solubilities and the physico-chemical properties in all studied systems were measured. The dry-salt diagram and water phase diagram of the quaternary system and the meta-stable diagrams of the ternary systems were plotted. The diagrams of the physico-chemical properties via the solution compositions in all systems were presented.First, when Li⁺ and Ca²⁺ coexisted in brine samples, the measurement of calcium ion with EDAT titration method is interfered by coexisted lithium ion. The interference-free method of Ca²⁺ titration with EDAT has been established when the concentration of Li⁺ is in high level. Meanwhile, the measurement of Li⁺ in brine was further disscussed, and the method of ICP-AES for Li⁺ measurement was finally confirmed.The meta-stable diagram of the ternary system Na⁺,Ca²⁺//Cl^--H₂O has one con-saturated point, two isothermal solubility curves and two crystallized zones corresponding to two single salts at 15℃and 35℃.The meta-stable system is a simple con-saturated type, and there are neither complex salts nor solid solutions formed. The calculated values of densities and refractive index in the ternary system are in good agreement with experiment values at 15℃.The meta-stable diagram of the ternary system Li⁺,Ca²⁺//Cl^--H₂O have two eutectic points, three isothermal solubility curves and three crystallized zones corresponding to three single salts at 15℃. The optical properties of the double-salt CaCl₂·LiCl·5H₂O were gained, and the optical properties of the man-made crystallization of LiCl·H₂O was also further confirmed. The meta-stable ternary system Li⁺,Na⁺//Cl^--H₂O is a simple eutectic type at 15℃. There has one eutectic point, two isothermal solubility curves and two crystallized regions corresponding to single salts of NaCl and LiCl·H₂O.As to the meta-stable diagram of quaternary system Li⁺,Na⁺,Ca²⁺//Cl^--H₂O at 15℃, there are two invariant points corresponding to CaCl₂·6H₂O +NaCl + CaCl₂·LiCl·5H₂O and LiCl·H₂O + NaCl + CaCl₂·LiCl·5H₂O, five co-saturated curves, and four co-saturated crystallizing zones corresponding to LiCl·H₂O, CaCl₂·6H₂O, LiCl·CaCl₂·5H₂O and NaCl. It was found that the physico-chemical properties in the meta-stable equilibrium solution are in changed regularly with the increasing of CaCl₂ concentration and the distinguished points are exited at the invariant points.The single-salt Pitzer parameters, Pitzer mixing parameters and the equilibrium constant of NaCl and CaCl₂ were respectively fitted using the solubility data of metastable ternary system NaCl-CaCl₂-H₂O at 15℃and 35℃. The mixing Pitzer parameters and the equilibrium constant of LiCl·CaCl₂·5H₂O in the system LiCl-CaCl₂-H₂O were also fitted according to the stable ternary system data at 25℃.