Metastable Equilibria Of The Quarternary System Li～+,K～+,Mg～(2+)//SO₄～(2-)-H₂O And Its Ternary Subsystem

In this dissertation, the metastable equilibria of the quaternary system Li+,K+,Mg²⁺// SO₄⁽2-_-H₂O at 15℃and its ternary subsystem K+,Mg²⁺//SO₄⁽2-_-H₂O at 15℃and 35℃were studied respectively with the method of isothermal evaporation. The solubilities of the composition and physicochemical properties such as density, refractive rate, viscosity, pH index, conductivity and total dissolved salt in the solutions were aLiSo measured. Then, the metastable phase diagrams of the ternary system, and the dry salt phase diagram and the water phase diagram of the quaternary system as well as the physicochemical via composition in the solution were plotted.In the metastable phase diagrams of the ternary system K+,Mg²⁺//SO₄⁽2-_-H₂O both at 15℃and 35℃, there are two co-saturated points, three solubility curves and three crystallizing zones. Comparison of the metastable phase diagrams at different temperatures respecitvely shows the crystallizing zone of K2SO4 at 35℃is larger than that at 15℃. When compared the metastable and stable phase diagrams at the same temperature, it is found the metastable phenomena of MgSO4 is more obvious. The calculated densities of the ternary system using the empirical equation reported in literature are in good agreement with the experimental values.In the metastable phase diagram of the quaternary system Li+,K+,Mg²⁺//SO₄⁽2-_-H₂O at 15℃, there are three invariant points of four co-existed phases, seven univariant metastable solubility curves and five crystallizing zones. When compared with the equilibrium phase diagram of the system at 35℃, it shows that the metastable effect of MgSO4 is more obvious, and the crystallizing zones of MgSO4?7H₂O and K2SO4 are much larger than those in the stable phase diagram. The physicochemicalproperties of the quaternary system are varied regularly according to the changes of composition in aqueous solutions. The calculated data of densities and refractive indexes in the quaternary system using the empirical equation reported are in a well match with the measured values.The predictive equilibrium phase diagram of the ternary system K+,Mg²⁺// SO₄⁽2-_-H₂O and the quaternary system Li+,K+,Mg²⁺//SO₄⁽2-_-H₂O at 25℃were calculated using Pitzer Modelling. The phase diagram plotted with the calculated values and the experimental values reported in literature of the ternary system at 25℃do not match with each other satisfactorily. While the calculated solubilities of the quaternary system are in good agreement with the data reported in literature at 25℃.