Electrolytic separation of Dy from Sm in molten LiCl-KCl using Pb-Bi eutectic alloy cathode

Abstract

• The reduction mechanism of Dy and Sm on liquid Pb-Bi eutectic was systematically investigated. • The separation of Dy from Sm on liquid Pb-Bi eutectic and the formation of PbBi, Pb 3 Dy and BiDy compounds. • DPV was used to monitor the progress during the separation process of pulse electrolysis. • The separation factors (SF Dy/Sm ) of the Dy/Sm couple was 786 and the extraction efficiency of Dy reached up to 98.9%. To study the application prospect of binary Pb-Bi eutectic (LBE) alloy electrode in pyroprocessing, the reduction mechanisms of Sm(III) and Dy(III) on W, liquid Bi, liquid Pb, and LBE alloy electrodes were explored. The reduction of Dy(III) and Sm(III) on LBE alloy electrode were found to proceed in one-step and two-step reactions, respectively. The reduction peaks of Dy(III)/Dy(0) and Sm(II)/Sm(0) on LBE alloy electrodes were −1.31 V and −1.56 V (vs. Ag/AgCl), respectively, which were located between the individual liquid Pb and liquid Bi electrodes. Then, the reduction process of Ln (Sm and Dy) in LiCl-KCl-BiCl 3 -PbCl 2 melt on the W electrode were also investigated to get more information on intermetallic compounds. The electrochemical separation of Dy from Sm was performed on the LBE alloy electrode by pulse potential electrolysis (PPE). X-ray diffraction analysis indicated the predominant separation products to be Pb 3 Dy and BiDy. The concentrations of Sm(III) and Dy(III) were monitored by differential pulse voltammetry and analyzed by ICP-MS. The average relative measurement errors obtained were 6.2% and 7.7% for SmCl 3 and DyCl 3 , respectively. The highest extraction efficiency of Dy could reach 98.9%, and the separation factors (SF Dy/Sm ) of Dy and Sm are reached up to 786.