The effect of iron-oxidising bacteria on the stability of gold (I) thiosulphate complex

Shuster, Jeremiah, Bolin, Trudy, MacLean, Lachlan C. W. and Southam, Gordon (2014) The effect of iron-oxidising bacteria on the stability of gold (I) thiosulphate complex. Chemical Geology, 376 52-60. doi:10.1016/j.chemgeo.2014.03.017

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Author Shuster, Jeremiah
Bolin, Trudy
MacLean, Lachlan C. W.
Southam, Gordon
Title The effect of iron-oxidising bacteria on the stability of gold (I) thiosulphate complex
Journal name Chemical Geology   Check publisher's open access policy
ISSN 0009-2541
Publication date 2014-05
Sub-type Article (original research)
DOI 10.1016/j.chemgeo.2014.03.017
Open Access Status
Volume 376
Start page 52
End page 60
Total pages 9
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Collection year 2015
Language eng
Abstract An acidophilic, iron-oxidising bacterial consortium was collected from Rio Tinto near Berrocal, Spain. This primary enriched culture was used to examine the effect of acidophilic iron-oxidising bacteria on the stability of soluble gold (I) thiosulphate. Stationary phase cultures and separate components of the cultures (i.e., aqueous ferric iron, iron oxyhydroxide precipitates and non-mineralised bacterial cells) were exposed to gold (I) thiosulphate solutions forming different experimental-gold systems. These experimental systems rapidly removed gold from solutions containing 0.002 mM–20 mM gold thiosulphate. Scanning and transmission electron microscopy demonstrated that the different culture fractions immobilised gold differently: the entire bacterial culture-gold systems precipitated 100 nm-size gold colloids; aqueous ferric iron–gold systems precipitated colloidal gold sulphide that ranged in diameter from 200 nm to 2 μm; iron oxyhydroxide-gold systems precipitated 5 nm-size gold sulphide colloids; and the bacteria-gold systems precipitated gold colloids ~ 2 nm in size along the bacterial cell envelope. Aqueous and solid ferric iron was critical in the destabilisation of the gold (I) thiosulphate complex. Analysis of the entire bacterial culture-, aqueous ferric iron- and iron oxyhydroxide-gold systems exposed to 2 mM gold using X-ray absorption near edge spectroscopy demonstrated that Au+ was immobilised from solution as gold sulphide (Au2S). The reaction between iron-oxidising bacteria and their ferric iron by-products with gold (I) thiosulphate demonstrated that thiosulphate ions would be an unstable gold complexing ligand in nature. Gold (I) thiosulphate is intuitively transformed into nanometer-scale gold sulphide or elemental gold within natural, acidic weathering environments with the potential to precipitate gold in jarosite that can subsequently be preserved in gossans over geological time.
Keyword Gold (I) thiosulphate
Gold sulphide
Colloidal gold
Iron-oxidising bacteria
Massive Sulfide Deposits
Iberian Pyrite Belt
Filamentous Cyanobacteria
Mine Drainage
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Earth Sciences Papers
Official 2015 Collection
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Citation counts: TR Web of Science Citation Count  Cited 2 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 3 times in Scopus Article | Citations
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Created: Thu, 26 Jun 2014, 15:37:35 EST by Gordon Southam on behalf of School of Earth Sciences