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Electrochemical Behavior of Scandium Ions in the LiCl-KCl Eutectic Melt
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DOI：10.1149/1945-7111/ae6373.png)
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Abstract
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The electrochemical behavior of Sc(III) ions in (LiCl-KCl)eut-ScCl3 (up to 2.75 mol%) melts was studied using cyclic voltammetry and chronopotentiometry at 773-873 K. It was established that the electroreduction of Sc(III) to Sc is a reversible process in the melts containing up to 0.7 mol% ScCl3. The presence of nucleation/growth processes was confirmed by Sc electrodeposition on a Mo substrate. The Sc(III) diffusion coefficients were determined using a new approach considering diffusion-controlled growth of nuclei. These values (from (1.3 +/- 0.1) & times; 10-5 cm2s-1 at 773 K to (2.3 +/- 0.1) & times; 10-5 cm2s-1 at 873 K) are approximately 10% higher and 30% lower than those calculated using the Berzins-Delahay and Sand equations, respectively. The concentration dependences of the limiting diffusion current density and the Sc(III)/Sc equilibrium potential were determined. The values of the Sc(III)/Sc apparent standard potential and the Sc(III) activity coefficient were found. The prospects for using scandium as a plutonium imitator during the development of spent nuclear fuel electrorefining modes were assessed. It was showed that the equilibrium and apparent standard potentials of Sc(III)/Sc and Pu(III)/Pu at 773 K and other equal conditions coincide, while the activity coefficients of Sc(III) are 3-4 orders of magnitude lower than those of Pu(III). The mechanism and kinetics of Sc(III) electroreduction on Mo electrode are studied at 773-873 K.The Sc(III) activity coefficients are 2.4 & times; 10-6 at 773 K and 6.7 & times; 10-5 at 873 K.The Sc(III)/Sc apparent standard potentials (vs Cl2/2Cl-) are -2.7761 V at 773 K and -2.6674 V at 873 K.The equilibrium and apparent standard potentials of Sc(III)/Sc and Pu(III)/Pu coincide at 773 K.Sc can be tested as a Pu imitator during the development of electrorefining modes.
Keywords:
electrode kinetics
electrodeposition
molten salts - high temperature molten salts
pyrochemical processing
thermodynamics
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3.3
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3.3W
Citations:
9.4W
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