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The electrochemistry of pyrite in chloride solutions

Nicol, M.ORCID: 0000-0002-8757-161X, Zhang, S. and Tjandrawan, V. (2018) The electrochemistry of pyrite in chloride solutions. Hydrometallurgy, 178 . pp. 116-123.

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A detailed study of the anodic and cathodic behaviour of natural pyrite in acidic chloride solutions containing various oxidants has been conducted as part of an overall program on the fundamental aspects of the heap leaching of copper sulphide minerals.

The stoichiometry of the anodic dissolution reaction depends on the potential in that it varies from less than 4F/mol Fe dissolved at potentials below 0.8 V(SHE) to 15F/mol Fe at potentials above about 1.0 V(SHE).

The mixed potentials of pyrite in chloride solutions containing iron(III) are greater than those in the presence of copper(II) and both increase with agitation as a result of enhanced transport of iron(II) and copper(I) from the surface of the dissolving mineral. The mixed potentials are unaffected by the presence of dissolved oxygen confirming the low reactivity for the cathodic reduction of oxygen.

The rate of anodic dissolution of pyrite in chloride solutions is independent of the acid and chloride concentration except at high chloride concentrations when the rate decreases slightly. The potential dependence of the anodic reaction roughly follows Tafel behaviour up to about 1.0 V but mechanistic conclusions are excluded due to the variable stoichiometry.

Cathodic reduction of oxygen is some 30 times slower than that of 1 g/L iron(III). The reduction of copper(II) is also less significant in the leaching of pyrite due to the lower formal potential of the copper(II)/copper(I) couple than that of the iron(III)/iron(II) couple in concentrated chloride solutions.

Comparative measurements have shown that pyrite will dissolve more slowly than chalcopyrite in chloride solutions and, this coupled to the low sulfate yield at low potentials, suggests that oxidation of pyrite as a source of heat in abiotic heap leaching is unlikely.

Item Type: Journal Article
Murdoch Affiliation(s): School of Engineering and Information Technology
Publisher: Elsevier BV
Copyright: © 2018 Elsevier B.V.
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