Investigation of Aqueous Biphasic Polyethylene Glycol Systems for the Selective Liquid/Liquid Extraction of Dissolved Metal Ions

这项建议涉及使用由聚乙二醇(PEG)和无机盐组成的双水相盐来分离溶解的金属离子。当向水中加入聚乙二醇和盐时，溶液分成两个不同的层；一个相富含聚乙二醇盐，另一个相含盐。溶解在该体系中的金属离子优先溶解在聚乙二醇富相中，因此，只需将聚合物和盐溶解在含金属的水溶液中，然后将其分离，就可以实现离子分离。影响金属分配的变量是pH、盐的选择、聚乙二醇的浓度、温度和到临界点的距离(即两相首先出现的聚合物/盐的组成)。提出了几个关键的研究领域：(I)在以前的研究中，PI已经在一系列间歇实验中证明，可以在不需要络合剂的情况下，用碳酸盐(K2CO3)和硫酸盐((NH4)2SO4)将TcO4-形式的TcO4-萃取到聚乙二醇富相中。PI打算进一步研究这一新的结果，并在此基础上找到一种方法，将金属离子从富含聚乙二醇相中剥离出来，完成分离过程。将测试几种方法，包括离子交换法和以聚乙二醇水相为水相的油水间歇萃取。(Ii)优化特定的两相体系(SO42-、CO32-、PO43-或碱性介质)，以选择性地去除(以CrO41-形式)的TC或Cr。(Iii)从高碱度和高硝酸盐浓度的合成废液中提取碱金属离子和碱土金属离子。(4)利用无机阴离子形成可萃取的金属络合阴离子来去除有毒金属阳离子的两相体系。(V)两相体系中的有机分离(Vi)使用双水相和水溶性萃取剂的组合萃取f元素。

This proposal is concerned with using aqueous biphasic salts composed of polyethylene glycol (PEG) and an inorganic salt to separate dissolved metal ions. When PEG and salt are added to water, the solution separates into two distinct layers; one phase is rich in PEG and the other in salt. Metal ions dissolved in this system preferentially dissolve in the PEG rich phase, and hence ion separation can be effected by simply dissolving polymer and salt in a metal-containing aqueous stream, and then separating the phases. The variables which affect the metal partitioning are the pH, salt selection, PEG concentration, temperature and distance from the critical point (i.e. the polymer/salt composition at which two phases first appear). Several critical areas are proposed for study: (i) In previous research, the PI has demonstrated in a series of batch experiments, that technetium in the form of TcO4- can be extracted into the PEG rich phase using carbonate (K2CO3) and sulphate ((NH4)2SO4 without the need of a complexing agent. The PI intends to study this novel result further, and to build on this discovery by finding a method to strip the metal ions from the PEG-rich phase and complete the separation process. Several methods will be tested including ion exchange, and oil-water batch extraction with the PEG as the aqueous phase. (ii) Optimize particular biphasic systems (SO42-,CO32-, PO43- or alkmaline media) for the selective removal of Tc or Cr (in the form of CrO41-). (iii) Base-Side extraction of alkali and alkaline earth metal ions from synthetic waste solutions of high alkalinity and high nitrate concentration. (iv) Biphasic systems for the removal of toxic metal cations using inorganic anions to form extractable complex anions of metals. (v) Organic separations in biphasic systems (vi) f-element extraction using a combination of aqueous biphase and water soluble extractant.