Journal article
A study of the gold colloid dissolution kinetics in oxygenated ammoniacal thiosulfate solutions
Hydrometallurgy, Vol.74(3-4), pp.243-257
2004
Abstract
Colloidal gold has a characteristic absorption peak at 530 nm that can be used to monitor the extent of gold dissolution in different lixiviant systems using an ultraviolet-visible spectrophotometer. This paper reports the kinetics of the dissolution of gold colloid in ammoniacal thiosulfate solutions using oxygen as a oxidant at pH 9.3-9.5 and temperature 25-48 °C. The relative rates of gold dissolution in different lixiviant systems are in descending order: oxygen-cyanide > copper(II)-ammonia-thiosulfate > oxygen-ammonia-thiosulfate > oxygen-ammonia > copper(II)-ammonia. The predominant gold(I) species in oxygenated thiosulfate solution based on the measured potentials on gold electrode is gold-thiosulfate complex (Au(S 2O3)23-). However, the measured potentials in the absence of thiosulfate are close to the reported values for the Au(NH3)43+/Au(NH3) 2+ couple, which indicates that disproportionation or oxidation of Au(NH3)2+ occurs. The initial rates of gold dissolution show reaction orders of ≈ 0.3 with respect to oxygen and ammonia, and are independent of the concentration of thiosulfate and chloride. The dissolution kinetics follow a shrinking core model with an activation energy of 25-37 kJ mol-1, indicating a mixed chemical-diffusion-controlled reaction.
Details
- Title
- A study of the gold colloid dissolution kinetics in oxygenated ammoniacal thiosulfate solutions
- Authors/Creators
- X.M. Zhang (Author/Creator) - Cooperative Research CentreG. Senanayake (Author/Creator) - Cooperative Research CentreM.J. Nicol (Author/Creator) - Cooperative Research Centre
- Publication Details
- Hydrometallurgy, Vol.74(3-4), pp.243-257
- Publisher
- Elsevier BV
- Identifiers
- 991005544929307891
- Copyright
- © 2004 Elsevier B.V
- Murdoch Affiliation
- Parker Cooperative Research Centre for Integrated Hydrometallurgy Solutions
- Language
- English
- Resource Type
- Journal article
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- Citation topics
- 7 Engineering & Materials Science
- 7.229 Mineral & Metal Processing
- 7.229.774 Bioleaching
- Web Of Science research areas
- Metallurgy & Metallurgical Engineering
- ESI research areas
- Materials Science