Phase Diagram of the Mixed Solvent System RbCl+CsCl+PEG1000+H2O and Application at 288.2 K
It is easy to form mixed crystals in chloride type aqueous solution because cesium and rubidium compound have similar properties and similar structures.The introduction of polyethylene glycol(PEG)in aqueous solution can change the properties of solvent,and then affect the law of crystallization salt,which is expected to achieve the separation of cesium rubidium mixed salts.In this work,the phase equilibrium with PEG mass fraction w％=20％and 40％for mixed solvent system RbCl+CsCl+PEG1000+H2O at 288.2 K were investigated by isothermal dissolution method,and the conceptual process of rubidium and cesium separation and purification based on phase diagram of mixed solvent system acquired by this work was proposed.Results show that only solid-liquid equilibrium relationship in the system RbCl+CsCl+PEG 1000+H2O at 288.2 K,and the phase diagram contains three crystal phase regions,corresponding to the single salt RbCl,CsCl and the solid solution[Csx,Rb1-x]Cl crystal region,respectively.With the con-tent of PEG1000 increase,the solubility of CsCl and RbCl in the mixed solvent gradually decreased,and the crystalline phase region of the two single salts increased.It can be shown that when w％=20％,crystal-line areas of the single salt RbCl and CsCl is much larger.According to the conceptual flow of rubidium and cesium separation and purification process,the product yield of RbCl was calculated with the initial mate-rial composition of wCsCl=0.400 0 and wRbCl=0.600 0 by adding two different mixed solvents.The results showed that the higher yield was obtained by adding R=40％of the mixed solvent(PEG1000+H2O).
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