Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (10): 2531-2537.doi: 10.3866/PKU.WHXB201606223

• ARTICLE • Previous Articles     Next Articles

Electrochemical Behavior of La(III) in Molten LiCl-KCl-LaCl3

Tao JIANG1,Jie TIAN1,Ning WANG1,Shu-Ming PENG1,*(),Mei LI2,Wei HAN2,Mi-Lin ZHANG2   

  1. 1 Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999, Sichuan Province, P. R. China
    2 Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, P. R. China
  • Received:2016-03-18 Published:2016-09-30
  • Contact: Shu-Ming PENG E-mail:pengshuming@caep.cn
  • Supported by:
    The project was supported by the Major Research Plan of the National Natural Science Foundation of China(91426302);and National Natural Science Foundation of China(21301163)

Abstract:

Electrochemical and thermodynamic studies on the formation of La-Ni intermetallic compounds in molten LiCl-KCl-(3.5%(w))LaCl3 at 773 K were performed. The electrochemical reduction of La(III) ions was investigated on inert W and reactive Ni electrodes by cyclic voltammetry. The reduction potential of La(III)/La on a Ni electrode was observed at more positive potential than that on a W electrode because of the formation of La-Ni intermetallic compounds when La ions reacted with the Ni substrate. Square-wave voltammetry, chronopotentiometry, and open-circuit chronopotentiometry provided further evidence for the formation of La-Ni intermetallic compounds. Potentiostatic electrolysis on a Ni electrode led to the formation of three La-Ni intermetallic compounds, LaNi5, La7Ni16 and La2Ni3, according to X-ray diffraction (XRD) and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) analyses. The standard Gibbs free energies of formation for LaNi5 were estimated from open-circuit chronopotentiometric measurements using the Gibbs-Helmholtz equation and Hess law. The formation of the La-Ni alloy layer could be controlled by the applied potential and time. Potentiostatic electrolysis was an effective method for electrochemical extraction of La.

Key words: LiCl-KCl-LaCl3, La-Ni, Alloy layer, Gibbs free energy

MSC2000: 

  • O641