Study of the Electrochemical Behavior and Thermodynamic Properties of Lanthanum Compounds on Inert Mo and Liquid Ga Electrodes in Fused NaCl-2CsCl Eutectic

Abstract

For extraction of metallic lanthanum from molten NaCl-CsCl-LaCl3 solutions, the electrochemical reduction of La(III) ions on inert Mo and liquid Ga electrodes was explored. Transient electrochemical techniques have been used to explore the reduction mechanism, transport parameters, and thermodynamics properties. The obtained results indicate that the electrochemical reaction of La(III) + 3ē → La on inert electrode is a single-stage irreversible process, which is controlled by the charge transfer rate. Simultaneously, the diffusion coefficient of [LaCl6]3- complex ions was obtained at different temperatures. The apparent standard potentials of La3+/La couple and La-Ga alloy vs. the temperature were determined. The base thermodynamic properties of lanthanum compounds were calculated. Furthermore, the potentiostatic method of electrolysis was used for the synthesis of La-Ga alloys.

Electrochemical Behavior of Neptunium in NaCl–2CsCl Melt

“…Furthermore, the diffusion coefficient values D(Np 3+ ) and D(Np 4+ ) in NaCl-2CsCl are close to those reported for other actinide or lanthanide ions. They are smaller than those in the 3LiCl-2KCl melt at the same temperatures, as reported for Cm 3+ and La 3+ ions, 16,24,30,35 because the diffusion coefficients of these metal element ions should be related to the viscosities of the melts. 36 3.4 Apparent redox potentials of Np 3© /Np 0 and Np 4© /Np 3© couples 3.4.1 The Np 3© /Np 0 couple Figure 8 shows the evolution of the potential after the cathodic polarization of the working electrode for NpCl 3 -(NaCl-2CsCl) melt at 823 K. Figure 9 shows the relationship between the molar ratio of NpCl 3 and the rest potentials obtained after the electrodeposition at each temperature.…”

“…The Np 3+ /Np 0 redox couple is irreversible under these experimental conditions because the potential of the cathodic peak becomes more negative with increasing sweep rates. Irreversible reactions on inert metal electrodes have been reported for the La 3+ /La 0 and Dy 3+ /Dy 0 couples in NaCl-2CsCl, 30,31 however the Cm 3+ /Cm 0 couple was assigned to a reversible reaction at sweep rates smaller than 100 mV/s. 24 Figure 3 shows the CVs for the Np 4+ /Np 3+ redox couple of NpCl 3 -(NaCl-2CsCl) melt at 823 K obtained with sweep rates from 50 to 500 mV/s.…”

Electrochemical Behavior and Preparation of La–Ni Alloy in LaF3–LiF-CaF2-La2O3 Molten Salt on Nickel Electrode

“…In addition, the value of αn in the irreversible process can be calculated as follows: E P − E normalp / 2 = 1.857 R T α n F where E p and E p/2 represent the peak potential (V) and the half-peak potential of the peak (V), respectively.…”