Electrochemical behaviors and electrolytic separation of Th(IV) and Ce(III) in ThF4-CeF3-LiCl-KCl quaternary melt

The extraction and recycle of thorium is an essential step in the thorium-uranium closed fuel cycle designed for Thorium-based Molten Salt Reactor system (TMSR), and the separation of thorium from FPs especially lanthanides is a key issue in the thorium recovery. In this paper, the electrochemical behaviors of Th(IV) and Ce(III) on Mo electrode were studied by cyclic voltammetry (CV) and chronopotentiometry (CP) techniques at 773 K in ThF4(3 wt%)/CeF3(0.3 wt%)-LiCl-KCl ternary melt and CeF3(0.3 wt%)-ThF4(3 wt%)-LiCl-KCl quaternary melt, respectively. The reduction peaks of Th(IV)/Th(0) and Ce(III)/Ce(0) were at −1.83 V and −2.21 V (vs. Ag/AgCl) in the respective ternary melt, respectively, which were same with the values in the quaternary melt; however, the oxidation peaks in the CeF3-ThF4-LiCl-KCl melt shifted negatively about 0.1 V. Pulsed potential electrolysis of quaternary melt revealed that 98.9% of Th(IV) can be electrochemical separated from the melt with almost all cerium remaining in the melt, based on the inductively coupled plasma atomic emission spectrometer (ICP-AES) results.