Abstract
In this study, we paid attention to separate and recover samarium, europium and gadolinium, which are typical rare-earth metals. Since rare-earth metals have almost the same property, it is very difficult to separate them from each other. Instead of using conventional solvent extraction and ion-exchange methods, a microcapsule method was employed in this work. Chemical method has generally been used in preparing microcapsules. We used here in situ polymerization method among them.
In this study, a fundamental investigation of the mutual separation of samarium, europium and gadolinium from an aqueous solution by using microcapsules containing a metal extractant was undertaken. As the extractant, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA) was used. The extractant was successfully encapsulated in microcapsules during in situ microencapsulation process. Metals extractabilities into the microcapsules were examined from metal ions extraction isotherm. The extraction behaviour of the metals was well explained by using the Langmuir adsorption isotherm model. According to the Langmuir adsorption model, the saturation amount of metal extracted and the extraction equilibrium constant were determined. The microcapsules containing EHPNA were found to be suitable for the extraction of the rare-earth metals. Using a reactor in which two columns packed with the microcapsules are connected in series, the separation and recovery of the metals was examined. In this way, the mutual separation of the rare-earth metals could be almost achieved by feeding a suitable eluent stepwise into the column.
