Selection of Solvents and Their Diluents for Solvent Extraction of Metals

本文从动力学和平衡的角度阐述了螯合剂萃取金属时溶剂及其稀释剂选择的基本概念。研究了微乳液萃取金属的方法，为金属萃取提供了新的分离领域。结果表明：1)吸附在界面上的1:1金属配合物与溶解在水相中的溶剂之间的反应决定了商用螯合剂对金属的萃取速率。三个因素,即。溶剂在水相和有机相之间的分配、溶剂在界面上的吸附过程以及溶剂质子解离的平衡常数对溶剂和稀释剂的最佳选择具有重要意义。工业用途的溶剂在性质上具有界面活性，吸附过程不如其他两个因素重要。2)螯合剂分子中烃基的链长对配分系数有影响，与酸性有机磷化合物不同。然后，需要一种基于量子化学的方法来获得溶剂及其稀释剂选择的依据。3)结果表明，微乳液辅助金属分离是可行的。该体系的金属萃取平衡由库仑相互作用决定。热力学分析也用于控制微乳液滴的大小与水相的矿化度。我们目前正在计划研究由两亲性试剂组成的有组织组合物的稳定性和与该组合物有关的相图。

This research is concerned with elucidating the basic concept of selecting the solvents and their diluents for metal extraction with chelating agents, from the view points of kinetics and equilibrium. Metal extraction with microemulsion is also studied for providing alternative separation field for metal extraction. The results obtained are as follows: 1)the reaction between the 1:1 metal complex absorbed on the interface and the solvent dissolved in the aqueous phase determines the rates of metal extraction with chelating agents of commercial use. Three factors,i.e., the partition of the solvent between the aqueous and the organic phases, the adsorption process of the solvent on the interface, and the equilibrium constant of proton dissociation of the solvent are important for the optimal choice of the solvents and diluents. The solvent of commercial use has interfacial activity in nature, and the adsorption process is less important than the other two factors. 2)The chain length of the hydrocarbon group in a chelating agent molecule has an effect on the partition coefficient,which is different from that for acidic organophosphorous compunds. Then, an approach based on quantum chemistry is needed for obtaining the basis of solvent and its diluent selection. 3) It was shown that the metal separation with the aid of microemulsion is feasible. The metal extraction equilibrium for this system is determined by the Coulomb interaction. Thermodynamic analysis was also carried out for controlling the size of the microemulsion droplets with salinity for the aqueous phase. We are now planning the researches on the stability of the organized assemblies composed of amphiphilic agents and the phase diagrams concerned with this assemblies.