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The electrochemical behaviour of enargite in ammoniacal solutions. II. Cathodic reactions

Nicol, M.J.ORCID: 0000-0002-8757-161X, Ruiz-Sánchez, A., Senanayake, G., Tjandrawan, V. and Lapidus, G.T. (2019) The electrochemical behaviour of enargite in ammoniacal solutions. II. Cathodic reactions. Hydrometallurgy, 189 . Article 105115.

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A detailed electrochemical study has been made of the cathodic reduction of copper(II) ions and dissolved oxygen on an enargite electrode in ammoniacal sulfate and chloride solutions under ambient conditions. The rate of the reduction of copper(II) to copper(I) on an enargite surface in ammoniacal sulfate solutions is rapid and can be described in terms of a quasi-reversible system. The rate is first-order in the concentration of copper(II) ions and is sensitive to mass transport even at low overpotentials. The kinetics and mechanism in chloride solutions are quantitatively similar to those in sulfate solutions. The rate of reduction decreases with increasing ammonia and ammonium ion concentrations and a model has been developed in which the rate is approximately proportional to the concentration of the tri-ammine copper(II) species, the concentration of which decreases as the concentrations of ammonia and ammonium ions increases.

The rate of reduction of dissolved oxygen is very much slower than that of copper(II) and occurs in two steps with peroxide as the intermediate species. The dissolution of enargite in oxygenated ammoniacal solutions containing copper(II) ions occurs as a typical redox-mediated mechanism in which oxygen re-oxidises copper(I) produced by reduction of copper(II) on the enargite surface i.e. copper(II) is the effective oxidant.

Item Type: Journal Article
Murdoch Affiliation(s): College of Science, Health, Engineering and Education
Publisher: Elsevier BV
Copyright: © 2019 Elsevier B.V.
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