Electrochemical behavior and electrolytic extraction of Ce(III) in CaCl2-CaF2 molten salt

The efficient recovery of the radioactive elements uranium (U) and plutonium (Pu) from radioactive calcium fluoride slag is of great significance for the sustainable utilization of nuclear resources and environmental protection. Molten salt electrolysis technology based on pyrometallurgy, characterized by a streamlined process and the absence of secondary waste generation, is widely regarded as the most promising approach for the treatment of such radioactive residues. However, the physicochemical properties of molten salts and the underlying electrode reaction mechanisms under high-temperature conditions remain insufficiently understood and lack systematic investigation. In this study, by comparing the electrochemical parameters and physical-chemical properties of different molten salt systems, it was found that the CaCl 2 -CaF 2 molten salt system is a suitable choice for treating radioactive calcium fluoride waste. Due to the high radioactivity of plutonium (Pu), cerium (Ce) was employed as a chemical analogue of plutonium to investigate the electrochemical extraction of actinides in CaCl 2 -CaF 2 molten salt systems. The electrochemical behavior of Ce(III) on a W electrode and related kinetic parameters were investigated. Electrochemical analysis reveals that Ce(III) undergoes a quasi-reversible and diffusion-controlled reduciton on inert W electrode. The process shows distinct adsorption and desorption, likely attributable to the coexistence of Cl − and F − ions. To better extract Ce, nickel (Ni) ions were introduced into the molten salt. The co-deposition behavior of Ce(III) and Ni(II) on the W electrode was investigated by electrochemical methods. The thermodynamic parameters of Ce-Ni intermetallic compounds at the experimental temperature were calculated. The results show that CeNi 5 has a distinct thermodynamic advantage in formation. X-Ray Diffraction (XRD)， Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS) characterization analyses confirmed the successful extraction of Ce in the form of the CeNi 5 intermetallic compound.