Electrochemical Behavior Of Pr(?) On Zn, Bi Electrodes And Anodic Dissolution Of Alloy In Molten Melts

In this paper, the electrochemical behavior and electrodeposition mechanism of Pr?III? and anodic dissolution of Bi-Pr-Li alloy were investigated in LiCl-KCl molten salts. And extraction of rare earths from molten salts was explored by co-deposition method. These results will provide fundamental data for the separation and extraction of actinides. The main works were listed as follows:1. The electrochemical behavior of Pr?III? ions in LiCl-KCl-PrCl₃ melt on an inert W electrode was investigated in the temperature range from 723 to 873 K by electrochemical techniques, such as cyclic voltammetry, square wave voltammetry,chronopotentiometry and open ciruit chronoptentimetry. The results from cyclic voltammogram and square wave voltammogram showed that the electrochemical reaction of Pr?III? to Pr?0? was an one-step 3-electrons exchanged. A series of CVs obtained at different temperature and scan rate indicated that the reduction of Pr?III?was controlled by mass transfer and revisable process at scan rate lower than 0.09 V s^-1.And the diffusion coefficient of Pr ?III? was calculated at different. According to the Arrhenius equation, the activation energy of Pr?III? ions in LiCl-KCl melts was found to be 31.96 kJ mol-1.2. The electrode behaviors of LiCl-KCl-PrCl₃ solutions on liquid Zn and Bi electrodes were studied by electrochemical techniques. The redox potentials of the Pr?III?/Pr couple on the liquid electrodes Zn and Bi were observed at more positive potentials values than those on one inert electrode. Cyclic voltammograms on liquid Zn and Bi pools electrodes were obtained at different scan rate, which suggested that electrochemical reactions of the Pr?III? were reversible. Cyclic voltammetry, square wave voltammetry, chronopotentiometry and open circuit chronopotentiometry were also conducted on Zn or Bi film electrodes. The results showed that the underpotential deposition of Pr on Zn or Bi film electrodes occurred due to the formation of Zn-Pr and Bi-Pr intemetallic compounds. The activities and relative partial molar Gibbs energies of Pr in Pr-Zn and Pr-Bi alloys were obtained by open circuit chronopotiometry at different temperature. The standard Gibbs energies of formation for the Pr-Zn and Pr-Bi intermetallic compounds were also calculated. The alloys of PrZn₁1?Pr₂Zn₁7?Pr₁3Zn₅8 and BiPr were prepared by potentiostatic electrolysis, and characterize by ICP-AES, XRD, SEM and EDS.3 .The anodic dissolution of Bi-Pr-Li alloy was explored in blank LiCl-KCl at 773 K by cyclic voltammetry, square wave voltammetry, chronopotentiometry and anodic stripping voltammetry. The dissolution equilibrium potentials and anodic dissolution sequence of various alloys was obtained at various time intervals during the dissolution of Bi-Pr-Li alloy by cyclic voltamometry and square wave voltammetry in blank LiCl-KCl molten salts. The diffusion coefficient of Pr?III? was calculated by chronopotentiometry. The on-line monitoring was performed during process of the anodic dissolution.