Selective extraction of gadolinium from Sm2O3 and Gd2O3 mixtures in a single step assisted by MgCl2 in LiCl–KCl melts

Abstract

The chloration of MgCl2 was studied in the LiCl–KCl–MgCl2–Gd2O3–Sm2O3 melts. Gd(III) and Sm(III) ions were observed by cyclic voltammetry and square wave voltammetry assisted by MgCl2 in melts. X-ray diffraction (XRD) patterns of melts indicated Gd2O3 and Sm2O3 were chlorinated by MgCl2 and formed GdCl3 and SmCl3. XRD patterns of non-dissolved residues, which were left after the melts were washed with water to remove the soluble salt, showed that the new compounds (i.e., GdOCl, SmOCl, MgO, Gd(OH)3, and Sm(OH)3) were produced. Potentiostatic electrolysis experiments were performed to extract Gd from Gd2O3 and Sm2O3 mixtures assisted by MgCl2. Separation between Gd2O3 and Sm2O3 was also achieved in a single step with the formation of Mg–Li–Gd alloys. XRD patterns of alloys indicated that Mg3Gd phase was formed. Scanning electron microscope images with energy dispersive X-ray spectroscopy showed Gd elements were mainly distributed in the grain boundary.