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ArticleName Mass transfer regimes during polarization of liquid metal electrode in molten salts and current efficiency
DOI 10.17580/tsm.2019.09.05
ArticleAuthor Mikhalev Yu. G., Zharinova N. Yu.

Siberian Federal University, Krasnoyarsk, Russia:

Yu. G. Mikhalev, Professor at the Department of Physical and Inorganic Chemistry, e-mail:
N. Yu. Zharinova, Associate Professor at the Department of Geography


Due to mobility of electrode/electrolyte interface, the polarization of liquid metal electrodes in molten salts enables a variety of mass transfer conditions (regimes). As a result, the current efficiency value in fused electrolysis with liquid metal electrodes can have a wide range of variability. In electrowinning of metals in molten salts at given current density or potential, the current efficiency is mainly dictated by metal solubility and the flows of dissolved metals (metal sub-ions) from cathode to anode. The flow of sub-ions is dictated by the intensity of mass transfer at the cathode surface characterized with the mass transfer coefficient, which can vary by orders of magnitude depending on the mass transfer conditions or regimes at the electrode/electrolyte interface. Equations have been deduced that show a relationship between the current efficiency in electrowinning and the mass transfer intensity for potentiostatic and galvanostatic electrolysis conditions. With the help of these equations one can estimate the current efficiency for different mass transfer coefficients at given cathode current densities or overvoltage values and solubility of the target metal and the background electrolyte metal. Analysis of the resultant equations and the current efficiency suggested by them shows that in potentiostatic conditions the metal losses do not depend on the mass transfer intensity but are rather governed by overvoltage and the concentrations of the sub-ions of the target metal and the background electrolyte metal at the electrode/melt interface. In galvanostatic conditions the current efficiency is dictated by the mass transfer regime at the electrode/ electrolyte interface. Thus, it decreases as the mass transfer intensity rises.

keywords Electrode, current efficiency, sub-ions, current density, overvoltage, flows of sub-ions, structures, mass transfer regimes, mass transfer coefficient

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