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Does galvanic coupling with pyrite increase the rate of dissolution of chalcopyrite under ambient conditions? An electrochemical study

Nicol, M.J.ORCID: 0000-0002-8757-161X (2022) Does galvanic coupling with pyrite increase the rate of dissolution of chalcopyrite under ambient conditions? An electrochemical study. Hydrometallurgy, 208 . Art. 105824.

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The role of galvanic coupling of chalcopyrite and pyrite in the enhanced rate of dissolution of chalcopyrite in acidic sulfate and chloride solutions at 30 °C has been defined in a detailed electrochemical study.

The results indicate that, under ambient conditions, the effect of galvanic contact with pyrite only marginally increases the rate of dissolution of chalcopyrite in both sulfate and chloride solutions containing iron(III) despite significant increases in the mixed potential of chalcopyrite. This has been shown to be due to the fact that the effect of potential on the rate of anodic oxidation of chalcopyrite is small in the relevant potential under these conditions. This is confirmed by the observation that the mixed potential and, therefore, the galvanic current is largely unaffected by a 4-fold decrease in pyrite surface area. The galvanic current transients compared well with potentiostatic current/time transients for chalcopyrite at the mixed potential observed during coupling.

In the case of copper(II) as the oxidant in chloride solutions, the galvanic currents are small due largely to the fact that the increase in chalcopyrite potential and decrease in pyrite potential are small as a result of the lower reduction potential of the copper(II)/copper(I) couple than the iron(III)/iron(II) couple. The galvanic currents with dissolved oxygen as the oxidant are significantly lower than with iron(III) as the oxidant and confirm the well-known fact that oxygen is less effective than iron(III) as an oxidant for chalcopyrite even when galvanic coupled to pyrite.

The electrochemical data obtained in this study indicate that the small galvanic currents observed do likely not account for the relatively large increases in rate previously observed in agitated leaching of chalcopyrite/pyrite slurries at elevated temperatures.

Item Type: Journal Article
Murdoch Affiliation(s): Engineering and Energy
Publisher: Elsevier BV
Copyright: © 2022 Elsevier B.V.
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