Electroextraction of gadolinium from Gd2O3 in LiCl–KCl–AlCl3 molten salts

Abstract

This work concerns directly the extraction of gadolinium from Gd2O3 by co-reduction with Al3+ in the LiCl–KCl–AlCl3 molten salts on the molybdenum and aluminum electrode, respectively, at temperature of 773K. Gibbs energy calculation shows that AlCl3 can favorably chloridize Gd2O3 and release Gd3+ ions. The electrochemical behaviors of Al3+, Gd3+ and the mechanisms of alloy formation were investigated by conducting a series of electrochemical techniques. Four typical signals were observed in cyclic voltammetry, square wave voltammetry and chronopotentiometry, while five plateaus were observed in open circuit chronopotentiometry, which might correspond to different kinds of Gd–Al intermetallic compounds. Potentiostatic and galvanostatic electrolysis were conducted to extract gadolinium from the LiCl–KCl–AlCl3 melts by the co-reduction method, and it was found that if the molybdenum cathode was used, GdAl2 particles would be deposited and adhere to a large amount of salt electrolytes. In contrast, when the aluminum plate was used as the cathode, a layer formed by potentiostatic electrolysis corresponding to an intermetallic compound (GdAl3) and three layers formed by galvanostatic electrolysis corresponding to three different Gd–Al intermetallic compounds such as GdAl3, GdAl2 and GdAl could be collected and identified through scanning electron microscopy (SEM)–energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis. Besides, electroextractions of gadolinium by co-reduction with Al3+ on the aluminum electrode have been performed with extraction efficiency of 89.7% for potentiostatic electrolysis and 96.5% for galvanostatic electrolysis, respectively.