Selection of Solvents and Their Diluents for Solvent Extraction of Metals

本研究从动力学和平衡学的角度阐明了络合金属萃取剂及其稀释剂选择的基本概念。并对微乳液萃取金属进行了研究，为金属萃取提供了可供选择的分离场所。结果表明：1)1：1金属络合物吸附在界面上与溶解在水相中的溶剂之间的反应决定了工业上使用的络合剂萃取金属的速度。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和溶剂的质子解离平衡常数三个因素对溶剂和稀释剂的最佳选择是重要的。工业用溶剂在自然界中具有界面活性，吸附过程不如其他两个因素重要。2)络合剂分子中碳氢基的链长对分配系数有影响，这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)实验结果表明，微乳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。还进行了热力学分析，以控制微乳液滴的大小与水相的盐度。我们正在计划对由两亲试剂组成的有序组装的稳定性和与此组装有关的相图进行研究。

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.