Advertisement

Dissolution of gold in oxidized bromide solutions

  • R. B. E. Trindade
  • P. C. P. Rocha
  • J. P. Barbosa

Abstract

Bromide stabilizes the auric ion by forming a stable complex in acidic aqueous solution. The oxidizing agent normally used in this process is the bromine. This is, however, a corrosive liquid with high vapour pressure and this is the main reason why it has not found acceptance yet as an industrial oxidant. In the present work, ferric ion, hydrogen peroxide and sodium hypochlorite were tested as alternative oxidants, alone or in combination, to evaluate the dissolution of gold in a bromide-containing aqueous solution. The advantage is that this is a cleaner technology and thus environmental protection costs may be minimized. Using the rotating disc technique, the effects of rotating speed, leaching time, temperature, oxidant concentrations, used together or separately, in an aqueous bromide solution with different concentrations of this complexant were evaluated. Ferric ion alone is able to dissolve gold, but kinetic rates are not elevated. Ferric ion and hydrogen peroxide can dissolve gold at higher rates. Hydrogen peroxide alone will not oxidize the gold and therefore the complex cannot be formed. Sodium hypochlorite alone, however, is able to promote the dissolution of gold in a sodium bromide solution. One of the main conclusions is that the gold dissolution obtained with the bromide solution as used in this work may, in some cases, be as good as or even superior to those obtained with the cyanidation process.

Keywords

Gold Bromide Rotating Disc Cyanide-free reagent 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Barbosa-Filho O. and Monhemius AJ.(1989) Thermochemistry of thyocyanate systems for leaching gold and silver ores, in Precious Metals′89 (eds. M.C. Jha and others), TMS-AIME, 307Google Scholar
  2. Bray W.C. and Livingstone R.S.(1923) The catalytic decomposition of hydrogen peroxide in a bromine-bromide solution and a study of the steady state, Journal of the AmericanChemical Society, 45, 1251CrossRefGoogle Scholar
  3. Chen C.K. et al. (1980) A study of the leaching of gold and silver by acidothioureation Hydro metallurgy, 5, 207Google Scholar
  4. Churchill M. and Laxen P.A.(1966) The rotating-disk system and its applications in the dissolution of gold, Research Report no. 16, National Institute for Metallurgy, Johannesburg, South AfricaGoogle Scholar
  5. Dadgar A. (1989) Extraction of gold from refractory concentrates, TMS-AIME annual meeting, Feb. 27-Mar. 2, Las Vegas, USAGoogle Scholar
  6. Dreisinger D. (1989) Enviromental issues in the aqueous processing of gold, Journal of Metals, 36Google Scholar
  7. Fink C.G. and Putnam G.L.(1942) Bromine process for gold ores, US Patent 2283198Google Scholar
  8. Habashi F. (1987) One hundred years of cyanidation, CIM Bulletin, 80, 108Google Scholar
  9. Hiskey J.B. and Atlury V.B. (1988). Dissolution chemistry of gold and silver in different lixiviants, in Mineral Process and Extractive Metallurgy Review, Gordon and Breach Publ., 4, 95CrossRefGoogle Scholar
  10. Kalocsai G.I.Z. (1987) Dissolution of noble metals, US Patent 4684404Google Scholar
  11. Kirk-Othmer Encyclopedia of Chemical Technology (1982) 3rd. ed., 4, John Wiley & Sons, New York, USAGoogle Scholar
  12. Levich V.G.(1962) Physicochemical Hydrodynamics, Prentice-Hall, Englewood Cliffs, New Jersey, USAGoogle Scholar
  13. Liebhafsky H.A. (1934) The equilibrium constant of the bromine hydrolysis and its variation with temperature, Journal of the American Chemical Society, 56, 1500CrossRefGoogle Scholar
  14. Monhemius A. J. (1987) Recent advances in the treatment of refractory gold ores, proc. XII International Meetting on Mineral Treatment and Hydrometallurgy, Rio de Janeiro, 2, 281Google Scholar
  15. Pesic B. and Sergent R.H. (1993) Reaction mechanism of gold dissolution with bromine, Metallurgical Transactions B, 24B, 419CrossRefGoogle Scholar
  16. Southampton Electrochemistry Group (1990) Instrumental Methods in Electrochemistry, Ellis Horwood Ltd., West Sussex, EnglandGoogle Scholar
  17. Trindade R.B.E. and Monhemius A.J. (1993) The use of anthraquinone as a catalyst in the cyanide leaching of gold, Minerals Engineering, 6, 565CrossRefGoogle Scholar
  18. von Michaelis H.(1987) Alternative leach reagents, Engineering and Mining Journal, 42Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 1994

Authors and Affiliations

  • R. B. E. Trindade
    • 1
  • P. C. P. Rocha
    • 1
  • J. P. Barbosa
    • 1
  1. 1.CETEM—Center for Mineral TechnologyCidade UniversitáriaRio de JaneiroBrazil

Personalised recommendations