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Hydrometallurgy ’94 pp 425–440Cite as

Iodide—thiocyanate leaching system for gold

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Abstract

The leaching of gold by thiocyanate solutions is performed at pHs between 1 and 2, which allows the use of iron(III) as an oxidizing agent. The mechanism of dissolution of gold by iron(III)-thiocyanate solutions is directly linked with the autoreduction process, in which FeIII is spontaneously reduced to FeII while oxidizing SCN- This oxidation proceeds through the formation of several intermediate species, particularly (SCN)2 and (SCN)3-, which act both as oxidants and, upon reduction, as complexants for gold. The production of (SCN)2 and (SCN)3- must be continuous due to their fast decomposition by hydrolysis. The instability of these intermediate species towards hydrolysis is a major drawback of the iron(III)-thiocyanate leaching system, which can be overcome by additions of small amounts of I- and/or I2. Experiments revealed a synergistic effect of the thiocyanate-iodide mixture on the dissolution of gold. The dissolution rates in the mixed system were substantially higher than those obtained when either iron(III)-thiocyanate or iron(III)-iodide were used separately. The synergistic effect was attributed to the formation of relatively stable mixed iodine-thiocyanate species such as I2SCN- and I(SCN)2- which participate in the mechanism of dissolution of gold.

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Author information

Authors and Affiliations

  1. Department of Materials Science and Metallurgy, Catholic University, Rio de Janeiro, Brazil

    O. Barbosa-Filho

  2. Department of Mineral Resources Engineering, Royal School of Mines, Imperial College of Science Technology and Medicine, London, England

    A. J. Monhemius

Authors
  1. O. Barbosa-Filho
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  2. A. J. Monhemius
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© 1994 Springer Science+Business Media Dordrecht

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Barbosa-Filho, O., Monhemius, A.J. (1994). Iodide—thiocyanate leaching system for gold. In: Hydrometallurgy ’94. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-1214-7_27

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  • DOI: https://doi.org/10.1007/978-94-011-1214-7_27

  • Publisher Name: Springer, Dordrecht

  • Print ISBN: 978-94-010-4532-2

  • Online ISBN: 978-94-011-1214-7

  • eBook Packages: Springer Book Archive

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