Phase Equilibria Of The Quaternary Systems Containing Lithium And Magnesium Ions At 15?

In this dissertation,the phase equilibria of the quaternary system?Li+,Na+,Mg+//S042+-H₂0?at 15 ? the quaternary system?Li+,Mg2+//Cl-?SO42--H₂0?at 15? and its ternary subsystem?Li+//C1-,5042-H₂0?at?15? and 35??were studied with the method of isothermal solution equilibrium,respectively.The solubilities and physicochemical properties including density,refractive index and pH values in the above mentioned systems were also determined.On the basis of experimental data,the phase diagrams and the physicochemical properties versus composition diagrams were all plotted.In the stable phase diagram of the ternary system?Li+//Cl-,SO42--H₂O?at 15?,there are one invariant point,two univariant curves and two crystallization regions.The similar structure can be found in this system at 35 ?.With the increasing of experimental temperature?15? to 35 ??,the crystallized area of LiCl·H₂O is decreased sharply,whereas the crystallization region of LiZSO4·HZO is increased.The solution densities,refractive index and pH value of the ternary system both at?15? and 35??change regularly with the increasing of lithium chloride concentration in solution.Based on the Pitzer ion-interaction model and its extended HW model of aqueous electrolyte solution,the solubility of the ternary system at?15? and 35 ??has been calculated.The predicted solubilities agree well with the experimental values.In the stable phase diagram of the quaternary system?Li+,Mg2+//Cl-,S042--H₂O?at 15?,there are foure invariant points,nine univariant solubility curves and six crystallizing zones.When compared with the stable equilibrium phase diagram of the system at 25 ?,the crystallized zone of MgSO4·5H₂O is found in the stable equilibriumat 25 ?;The crystallized area of MgSO4·7H₂O are decreased sharply,whereas the crystallization region of MgSO4·6H₂O and Li2SO4·H₂O are increased,meanwhile others are small and changing weakly,with the increasing of experimental temperature?15? to 25??.The physicochemical properties of the equilibrium solutions change regularly with the changing concentration of the system.In the stable phase diagram of the quaternary system?Li+,Na+,Mg2+//SO42'-H₂o?at 15?,there are two invariant points,five univariant solubility curves and four crystallizing zones.When compared with the stable equilibrium phase diagram of the system at 25?,the crystallized zone of Na2SO4.MgSO4·4H₂O is found in the stable equilibrium at 25 ?;the crystallized area of MgSO4·7H₂O and Na2SO4·10H₂O are decreased sharply,whereas the crystallization region of Li2SO4·3Na2SO4·12H₂O and Li2SO4·HZO are increased,with the increasing of experimental temperature?15 ? to 25 ??.The physicochemical properties of the equilibrium solutions change regularly with the changing concentration of the system.