Evaluation of the Electroextractions of Ce and Nd from LiCl-KCl Molten Salt Using Liquid Ga Electrode

The aim of this work is to explore the electroextractions and related thermodynamic properties of Ln (Ce and Nd) as actinide surrogates on the liquid Ga media, aiming at further Ln/An separation. The activities, activity coefficients and solubilities of Ce and Nd in the liquid Ga media were determined by open circuit potential at the temperature range from 698 to 798 K. The electroextractions of Ce and Nd and their corresponding current efficiencies on a static liquid Ga electrode were investigated by gavanostatic electrolysis. The electrochemical behaviors of Ce and Nd on a liquid Ga electrode in LiCl-KCl eutectic were explored by the cyclic voltammetry. It was found that both of the reductions of Ce(III) and Nd(III) on a liquid gallium electrode start at about −1.1 V at 773 K and are a one-step process with three electrons transferred. Semi-differential method was applied so as to more accurately determine the apparent standard potential of Nd(III)/Nd(II) which actually hadn't been well clarified in literatures. Open circuit potential technique was also utilized to determine the apparent standard potentials of Ce(III)/Ce and Nd(III)/Nd redox couples and to evaluate the thermodynamic properties of Ce and Nd in the liquid Ga media. Galvanostatic electrolyses on the static liquid Ga electrode were conducted to extract the Ln elements with or without the formation of intermetallic compounds at 723 or 773 K. The current efficiencies for the electroextraction of Ce and Nd were calculated to be about 90%. X-ray diffraction (XRD) characterizations identified the formation of intermetallic compounds CeGa 6 and NdGa 6 after the electrolysis. The Gibbs free energies for the formation of LnGa 6 were also calculated.