Electroreduction of cupric(II) ions at the ultramicroelectrodes from concentrated electrolytes – Comparison of industrial and laboratory prepared aqueous solutions of copper(II) ions in sulfuric acid electrolytes

The electroreduction of cupric ions has always attracted considerable attention because of its importance for both fundamental and applied aspects. In this paper, the electrodeposition of copper from concentrated real refinery and laboratory prepared electrolytes is investigated. The influence of the complex matrix present in industrial electrolytes (from which active animal glue and thiourea were removed) on the copper electrodeposition mechanism and kinetics was not sufficiently studied in the past. The same can be stated regarding the copper electroreduction investigations in concentrate electrolytes. The influence of potential and temperature on potentiostatic reduction of copper ions at gold ultramicroelectrodes in both electrolytes is studied by chronoamperometric methods. In both studied electrolytes the mechanism of copper nucleation was found to be diffusion controlled, 3D and progressive. The values of apparent bulk diffusion coefficients and the rates of copper nuclei formation in both industrial and synthetic electrolytes are estimated and compared. In both solutions the rate of nucleation increases with absolute value of potential and temperature. Increasing deposit potentials produces smaller nuclei and higher nuclei copper population density. In the whole studied temperatures and potentials ranges AN∞ changes from 3.30 × 109 to 2.50 × 1013 cm−2 s−2 in industrial and from 1.77 × 1010 to 1.49 × 1013 cm−2 s−2 in laboratory prepared electrolytes. The values of diffusion coefficients obtained for industrial and for laboratory prepared solutions do not differ markedly.