Studies On The Metastable Phase Equilibria Of The Quinary Systems Li⁺(Mg²⁺),Na⁺,K⁺,Rb⁺//Cl^--H₂O And Their Partial Subsystems At T=298.2K And 323.2K

Aiming to the phase equilibrium relationship of water and salt systems involved in the development of liquid mineral resources,the metastable equilibria of the quinary systems Li+?Mg2+?,Na+,K+,Rb+//Cl-H2O and their sub-systems at 298.2 K and 323.2 K are studied,which provides the theoretical basis and technological parameters for comprehensive utilization of chloride type Salt Lake brine.The specific research system of the dissertation covers:the quinary systems Li+;Na⁺,K⁺,Rb⁺//Cl^--H₂O at 298.2 K and 323.2 K;the quinary system Na⁺,K⁺,Mg²⁺,Rb⁺//Cl^--H₂O at 323.2 K;the quaternary system Na⁺,K⁺,Rb⁺//Cl^--H₂O at 298.2 K and 323.2 K;the quaternary system Li⁺,Na⁺,Rb⁺//Cl^--H₂O at 298.2 K and 323.2 K.According to the data of solubility and physicochemical properties of the equilibrium solution obtained from the experiment,the metastable dry-salt phase diagram,water content diagram and physicochemical property composition diagram of these systems are constructed respectively,and the solubility law of chloride salts in each system presented in the graph is summarized.The quaternary system Li⁺,Na⁺,Rb⁺//Cl^--H₂O at 298.2 K and 323.2 K,without double salt and solid solution formed,which belongs to simple system.The dry-salt phase diagram consists of one saturation point,three single variable curves and three crystalline regions.Although the change of temperature has influence on the solubility of LiCl,the order of the crystalline region in the phase diagram is NaCl>RbCl>LiCl·H20.The quaternary system Na⁺,K⁺,Rb⁺//Cl^--H₂O at 298.2 K or 323.2 K without double salt formed,while solid solution?K,Rb?Cl found in the solid phases of the system,thus this system belongs to a complex type.The metastable phase diagram of the system consists of two saturation points,five single variable curves and four crystalline regions.Compared with the phase diagrams of the system at 298.2 K and 323.2 K,it was found that the crystalline forms of salts have not changed,while the size of the crystallized zone has changed.With the increase of temperature,the solid solution area of NaCl and?K,Rb?Cl decreases,and that of KC1 increases.The comparison results show that the reduction temperature is beneficial to the precipitation of KCl during the evaporation process of the system.The quinary system Li⁺,Na⁺,K⁺,Rb⁺//Cl^--H₂O in the crystalline phase region of 298.2 K and 323.2 K,with solid solution?K,Rb?Cl appeared,which is of complex system.There are two saturation points,seven univariate curves,and six crystallization zones in the metastable dry-salt phase diagram at 298.2 K or 323.2 K.At different temperatures,the crystalline form of each salt has no change,while the size of the corresponding phase area has changed.As the temperature increases,the precipitation phase associated with?K,Rb?Cl solid solution decreases.The quinary system Na⁺,K⁺,Mg²⁺,Rb⁺//Cl^--H₂O is a complex system at 323.2 K.In the equilibrium solid phase,carnallite?KCl·MgCl2·6H2O?,rubidium carnallite?RbCl·MgCl2·6H2O?and solid solution based on potassium chloride and rubidium chloride?K,Rb?Cl are formed.The spatial three-dimensional dry-salt phase diagram of the system consists of four saturation points,thirteen single variable curves and thirteen crystalline regions.Due to the high solubility of MgCl2 in the system,and its easy formation of complex salts with other monohydrates in the form of hydrates,the saturation points of this system are concentrated in the vicinity of the MgCl₆·H₂O crystal phase region.