V. G. Kolyasnikov, A. M. Potapov, V. Yu. Shishkin, A. E. Dedyukhin, Yu. P. Zaikov.
ABSTRACT
The molten eutectic mixture LiCl-KCl is a promising medium for different high-temperature electrochemical processes of refining, separation, electrocrystallization, etc. It has a low melting point, low corrosion activity and a wide electrochemical window. The sequence of oxidation and electrodeposition of metals in electrolytes is determined by their electrochemical potentials.
The object of research is CdCl2 solutions in the molten LiCl-KCl eutectic. Cadmium chloride is studied as a promising agent for chlorination in molten salts.
The purpose of the present work is to evaluate the thermodynamic parameters of the CdCl2 interaction with the LiCl-KCl melt. The equilibrium electrode potentials of cadmium in the molten LiCl-KCl eutectic were experimentally measured with a cadmium chloride content of 0.25 to 20 mol % in the temperature range from 450 to 550°C, using EMF method. The values of conventional standard electrode potentials of cadmium were calculated and the temperature dependence of the isobaric-isothermal potential was determined. The increase in CdCl2 concentration and temperature rise leads to the shift of potentials to a more positive region.
Empirical equations of electrode potentials isotherms were obtained. The valency of cadmium cations calculated form the isotherms slope was fond equal to two.
The conditional standard electrode potentials of cadmium in the LiCl-KCl melt were calculated, temperature dependence was determined.
The values of the enthalpy and entropy of the CdCl2 formation reaction in the LiCl-KCl melt in the temperature range of 450–550°C are calculated: ∆H = -382.63 kJ/mol; ∆S = -119.66 J/mol∙K.
The Gibbs energy of the CdCl2 formation reaction in the LiCl-KCl melt increases with temperature rise.
KEYWORDS
Equilibrium potentials, conditional standard potential, EMF method, cadmium chloride
DOI: 10.31857/S023501062206007X