RbCl+CsCl+PEG1000+H_(2)O混合溶剂体系288.2 K相图及应用

Phase Diagram of the Mixed Solvent System RbCl + CsCl + PEG1000 + H_(2)Oand Application at 288.2 K

铷铯化合物盐性质相近、结构相似,在氯化物溶液中极易形成混晶,通过在水中引入聚乙二醇(PEG),形成聚乙二醇+水混合溶剂,有望影响铷铯混盐结晶析盐规律。论文采用等温溶解平衡法开展了288.2 K下混合溶剂体系RbCl+CsCl+PEG1000+H_(2)O〔溶剂中PEG1000的质量分数(w%)分别为20%、40%〕相平衡实验研究,提出了基于混合溶剂体系相图的铷、铯分离纯化工艺概念流程。研究结果表明,288.2 K下混合溶剂体系RbCl+CsCl+PEG1000+H_(2)O仅存在固-液相平衡关系,固液平衡相图包含3个结晶相区,分别对应RbCl、CsCl和固溶体[Cs_(x),Rb_(1-x)]Cl结晶区。随着混合溶剂中PEG1000质量分数R的增加,CsCl和RbCl在混合溶剂中的溶解度逐渐降低。比较而言,当w%=20%时,体系中的RbCl和CsCl单盐结晶相区面积更大。根据铷、铯分离纯化工艺概念流程,计算了初始组成为w_(CsCl)=0.4000,w_(RbCl)=0.6000时,添加两种不同混合溶剂时RbCl的产品收率,结果表明,w%=40%的混合溶剂(PEG1000+H_(2)O)获得的收率更高。

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+H_(2)O 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+PEG1000+H_(2)O at 288.2 K,and the phase diagram contains three crystal phase regions,corresponding to the single salt RbCl,CsCl and the solid solution[Cs_(x),Rb_(1-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 w_(CsCl)=0.4000 and w_(RbCl)=0.6000 by adding two different mixed solvents.The results showed that the higher yield was obtained by adding R=40%of the mixed solvent(PEG1000+H_(2)O).