Institute of High-temperature Electrochemistry of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia:

P. S. Pershin, Junior Researcher, e-mail: paffka19@yandex.ru
Yu. R. Khalimullina, Researcher
P. A. Arkhipov, Senior Researcher
Yu. P. Zaykov, Director

Electroreduction of ions is a cathodic process in lead refining technology. However, having certain conditions of electrolysis, cathodic process can involve not only lead, but also ions of other elements, which change the parameters of electrolysis and, as a result, worsen the quality of final product. The process of reduction of lead ions on molybdenum supporting plate, made of oxide-chloride melt LiCl – KCl – PbCl₂ – PbO, depend on concentration of lead oxide in the temperature range of 723–823 K. This dependence was researched due to the method of stationary galvanostatic polarization curves. It is shown that addition of lead oxide to electrolyte reduces the limiting diffusion current density of lead ions reduction. According to polarization curves form and its depending on temperature and lead (II) oxide concentration, there can be suggested that cathodic process of lead ions reduction is controlled by diffusion. This is connected with formation of oxide-chloride complex Pb₂OCl₂ in electrolyte, which is conformed to literature data. There is shown that particles of Pb₂O²⁺ have lower diffusion coefficients, than ions of Pb²⁺. Participation of such coarse particles in electrode process, leads to decreasing of limiting diffusion current density. This current density can be also under the influence of changing of concentration of electroactive particles. Further increasing of current density leads to smooth shift of electrode potential into negative area to isolation of alkaline metal and formation of lithium and lead alloy. Obtained data can be used for optimization of technology of lead refining in oxide-chloride melts.

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