Curtin University Homepage
  • Library
  • Help
    • Admin

    espace - Curtin’s institutional repository

    JavaScript is disabled for your browser. Some features of this site may not work without it.
    View Item 
    • espace Home
    • espace
    • Curtin Theses
    • View Item
    • espace Home
    • espace
    • Curtin Theses
    • View Item

    A Kinetic and electrochemical study of the dissolution of gold in aerated cyanide solutions: the role of solid and solution phase purity

    11442_Jeffrey Matthew 1997.pdf (6.851Mb)
    Access Status
    Open access
    Authors
    Jeffrey, Matthew I.
    Date
    1997
    Supervisor
    Dr Steve La Brooy
    Professor Ian Ritchie
    Type
    Thesis
    Award
    PhD
    
    Metadata
    Show full item record
    School
    School of Applied Chemistry
    URI
    http://hdl.handle.net/20.500.11937/2030
    Collection
    • Curtin Theses
    Abstract

    Over the last 100 Years, the cyanidation process has been the most popular method for recovering gold from its ores. Despite this, there are still efforts to improve the efficiency of the process, particularly as ores become more difficult to treat. Many investigators have studied the cyanidation process, although a large proportion of these studies have obtained contradictory results. This thesis presents a kinetic and electrochemical study of the leaching of gold in cyanide solutions, and emphasis is placed on rationalising the conflicting results which have been published in the past.The leaching rate of gold was measured using a rotating electrochemical quartz crystal microbalance, an instrument which allows the simultaneous measurement of electrochemical data and mass changes at the solid-solution interface in real time. A proportion of this project was devoted to the on-going design of this instrument, and a number of modifications are discussed in detail. Initially, the leaching of gold in cyanide solutions was investigated under conditions of high purity. Under these conditions, it was found that the gold surface is blocked by a passive film, presumably AuCN. The presence of such a film results in the reaction being chemically controlled, and under typical cyanidation conditions (4 mM cyanide, pH 10.0), the rate of dissolution is very low. These kinetic results were supported by complimentary electrochemical studies, which showed that gold is passive in the potential region where cyanidation occurs.The second part of this thesis presents a study of the effect of system purity on the leaching of gold in cyanide solutions. Solution phase purity was investigated by adding controlled amounts of lead or silver to the leach solutions. It was found that in the presence of low concentrations of lead, the dissolution of gold in 20 mM cyanide solutions was oxygen diffusion controlled (as compared to chemical control for gold in the absence of lead). However, high concentrations of lead were found to be detrimental to the leaching process. It is believed that the role of lead is to modify the surface by cementation, hence reducing the effect of the passive film. Silver was also found to be effective at reducing passivation, and the role of silver believed to be similar to that of lead. It was found that unlike lead, high concentrations of silver are not detrimental to the dissolution of gold in cyanide solutions.Solid phase purity was also found to be important in the leaching of gold, and it was found that the leaching of a gold sample which contains 1 % silver is diffusion controlled. This finding is important from an industrial viewpoint, as most native gold contains some silver. Consequently, attempts were made to rationalise the leaching of gold/silver with current plant practice. Discussion on the effect of cyanide and oxygen concentrations, temperature and lead addition is presented.

    Related items

    Showing items related by title, author, creator and subject.

    • Gold leaching in thiosulfate solutions and its environmental effects compared with cyanide
      Oraby, Elsayed A. (2009)
      Nowadays, keeping mining and the environment sustainable is a major concern all over the world. Using toxic chemicals such as cyanide and mercury in the gold leaching process is one of the main factors that need to be ...
    • Gold and copper leaching from gold-copper ores and concentrates using a synergistic lixiviant mixture of glycine and cyanide
      Oraby, E.; Eksteen, Jacques; Tanda, B. (2017)
      © 2017 Elsevier B.V.The presence of cyanide soluble copper in the cyanidation of gold-copper ores and concentrates significantly increases the cyanide consumption in order to achieve sufficient gold recovery. In addition, ...
    • Gold leaching in cyanide-starved copper solutions in the presence of glycine
      Oraby, E.; Eksteen, Jacques (2015)
      © 2015 Elsevier B.V. Abstract In the cyanidation of copper-gold ores, the presence of copper minerals can lead to soluble gold losses, the production of weak acid dissociable (WAD) cyanide, as well as a number of operational ...
    Advanced search

    Browse

    Communities & CollectionsIssue DateAuthorTitleSubjectDocument TypeThis CollectionIssue DateAuthorTitleSubjectDocument Type

    My Account

    Admin

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    Follow Curtin

    • 
    • 
    • 
    • 
    • 

    CRICOS Provider Code: 00301JABN: 99 143 842 569TEQSA: PRV12158

    Copyright | Disclaimer | Privacy statement | Accessibility

    Curtin would like to pay respect to the Aboriginal and Torres Strait Islander members of our community by acknowledging the traditional owners of the land on which the Perth campus is located, the Whadjuk people of the Nyungar Nation; and on our Kalgoorlie campus, the Wongutha people of the North-Eastern Goldfields.