Electrochemical Behavior And Electrochemical Extraction Of Cerium In Molten LiCl-KCl Salt

Cyclic voltammetry (CV), square wave voltammetry (SWV), chronopotentiometry (CP), and open circuit chronopotentiometry (OCP) techniques were employed to investigate the electrochemical behaviors of Ce(Ⅲ) ions on Mo, W, Al and liquid Zn electrode in LiCl-KCl eutectic at 773 K. The electroreduction of Ce(Ⅲ) on the inert Mo or W electrode takes place in a single electrochemical process with 3 electrons at about -2.05 V. When the reactive Al and liquid Zn electrode were employed, the reduction of Ce(Ⅲ) occurs at a more positive potential (-1.43 V for Al electrode and-1.4V for liquid Zn electrode) due to the formation of Ce-Al and Ce-Zn alloys, respectively, which leads to the decrease of Ce activity in the metal phase. In addition, the co-reduction behaviors of Ce(Ⅲ) with Al(Ⅲ) or Zn(Ⅱ) ions and electrochemical extraction of cerium from molten LiCl-KCl at the temperature of 773K were also conducted. The results revealed that Ce(Ⅲ) with Al(Ⅲ) cations and Ce(Ⅲ) with Zn(Ⅱ) cations can be co-reduced at the surface of the Mo or W electrodes by forming different kinds of Ce-Al and Ce-Zn alloys, respectively. Furthermore, the thermodynamic properties of forming ZnxCey intermetallic compounds in the LiCl-KCl eutectic were estimated from OCP measurements on a Zn-coated W electrode in the temperature range of 723-823 K. Finally, potentiostatic electrolysis at different deposition potentials on Al plate electrodes in LiCl-KCl-CeCl3-AlCl3 and inert W or liquid Zn electrodes in LiCl-KCl-CeCl3-ZnCl2 were also performed to prepare Ce-Al and Ce-Zn alloys, respectively. The deposition products were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS). It was found that in LiCl-KCl-CeCl3-AlCl3 system only one intermetallic compound (Al11Ce3) could be formed at the deposition potential of-1.6 V and two intermetallic compounds (Al11Ce3 and Al3Ce) could be formed at the potential of-1.9 V. When the deposition potential was negative than -2.1 V, cerium-rich alloy (AlCe) could be obtained on the surface of the Al electrode. In LiCl-KCl-CeCl3-ZnCl2 system, intermetallic compound CeZn11 can be prepared on both the inert W electrode and liquid Zn electrode.