Journal article
Catalytic role of ammonia in the anodic oxidation of gold in copper-free thiosulfate solutions
Hydrometallurgy, Vol.77(3-4), pp.287-293
2005
Abstract
Literature data is re-interpreted to show that the anodic oxidation of gold in ammoniacal thiosulfate solutions is dependent upon the concentration product [M 2S 2O 3][NH 3] to the order 0.8 (M=Na or NH 4). Analysis of chemical speciation in solution shows that the concentration of NH 4S 2O 3 - ion-pair is equal or larger than that of the unassociated S 2O 3 2- ion. A species distribution diagram for the gold(I)-ammonia-thiosulfate-hydroxide system in solutions of 1 M ammonium thiosulfate solutions containing 0.5-2 M ammonia at pH 10-11 shows that although Au(S 2O 3) 2 3- is the predominant complex (>99%), a small fraction of Au(S 2O 3)(NH 3) - is present. It is proposed that ammonia facilitates gold dissolution via oxidation of the surface adsorbed species Au(S 2O 3)(NH 3) 2- (ads). This oxidation corresponds to a rate constant of k Au=2.8×10 -4 mol m -2 s -1 to produce Au(S 2O 3)(NH 3) - (ads/aq) followed by desorption and re-equilibration in solution to Au(S 2O 3) 2 3-.
Details
- Title
- Catalytic role of ammonia in the anodic oxidation of gold in copper-free thiosulfate solutions
- Authors/Creators
- G. Senanayake (Author/Creator)
- Publication Details
- Hydrometallurgy, Vol.77(3-4), pp.287-293
- Publisher
- Elsevier BV
- Identifiers
- 991005542430907891
- 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