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

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-BiCl3-PbCl2 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 Pb3Dy 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 SmCl3 and DyCl3, respectively. The highest extraction efficiency of Dy could reach 98.9%, and the separation factors (SFDy/Sm) of Dy and Sm are reached up to 786.

Automated summary

The reduction mechanisms of Sm(III) and Dy(III) on different electrodes were explored, leading to successful separation of Dy from Sm using pulse potential electrolysis on a LBE alloy electrode. Analysis using differential pulse voltammetry and ICP-MS showed low relative measurement errors for monitoring the concentrations of Sm(III) and Dy(III).