کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6436651 1637595 2014 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The effect of iron-oxidising bacteria on the stability of gold (I) thiosulphate complex
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
The effect of iron-oxidising bacteria on the stability of gold (I) thiosulphate complex
چکیده انگلیسی


- Gold (I) thiosulphate is unstable in the presence of iron-oxidising bacteria.
- Gold (I) thiosulphate is unstable in the presence of ferric iron.
- Gold (I) thiosulphate is transformed into gold sulphide or elemental gold.
- Precipitate of gold in jarosite can be preserved in gossans over geological time.

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.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Geology - Volume 376, 29 May 2014, Pages 52-60
نویسندگان
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