Electrochemical Behavior and Extraction of Holmium on Cu Electrode in LiCl-KCl Molten Salt

Abstract

The electrochemical behavior of Ho (III) on Cu electrode was analyzed by transient electrochemical techniques. Cyclic voltammetry and square wave voltammetry experiments indicated that the deposition potential of Ho (III) shift toward more positive values on Cu electrode because of the formation of Cu-Ho intermetallic compounds. According to the results of open circuit chronopotentiometry, the thermodynamic data, such as standard molar Gibbs free energy, enthalpy and entropy of formation for each Cu-Ho intermetallics were calculated in the temperature of 773−893 K. Moreover, potentiostatic and galvanostatic electrolysis was conducted to extract holmium from molten slat on Cu electrode at 773 K. The extraction efficiency of Ho was found to be about 99.37% by potentiostatic electrolysis at −2.15 V for 20 h. The phase composition and morphology of the extraction products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS). The results revealed that Cu-Ho intermetallic compounds, Cu0.99Ho0.01, Cu5Ho and Cu2Ho were formed during electrochemical extraction. The effect of the applied potential on the formation rate of Cu-Ho layer was investigated.