Origin of Oxygen in Sulfate during Pyrite Oxidation with Water and Dissolved Oxygen:  An In Situ Horizontal Attenuated Total Reflectance Infrared Spectroscopy Isotope Study

FeS2 (pyrite) is known to react with water and dissolved molecular oxygen to form sulfate and iron oxyhydroxides. This process plays a large role in the environmentally damaging phenomenon known as acid mine drainage. An outstanding scientific issue has been whether the oxygen in the sulfate and oxy...

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Bibliographic Details
Published in:Environmental science & technology 2004-11, Vol.38 (21), p.5604-5606
Main Authors: Usher, Courtney R, Cleveland, Curtis A, Strongin, Daniel R, Schoonen, Martin A
Format: Article
Language:English
Subjects:
Deuterium - analysis
Dissolution
Earth sciences
Earth, ocean, space
Exact sciences and technology
Ferric Compounds - chemistry
Geochemistry
Industrial Waste - analysis
Iron - chemistry
Isotopes
Mineralogy
Mining
Oxidation
Oxidation-Reduction
Oxygen
Oxygen - chemistry
Oxygen Isotopes - analysis
Silicates
Spectrophotometry, Infrared
Spectrum analysis
Sulfates - chemistry
Sulfides - chemistry
Water
Water - chemistry
Water geochemistry
Water Pollutants - analysis
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Summary:FeS2 (pyrite) is known to react with water and dissolved molecular oxygen to form sulfate and iron oxyhydroxides. This process plays a large role in the environmentally damaging phenomenon known as acid mine drainage. An outstanding scientific issue has been whether the oxygen in the sulfate and oxyhydroxide product was derived from water and/or dissolved oxygen. By monitoring the reaction in situ with horizontal attenuated total reflectance infrared spectroscopy, it was found that when using 18O isotopically substituted water, the majority of the infrared absorbance due to sulfate product red-shifted approximately 70 cm-1 relative to the absorbance of sulfate using H2 16O as a reactant. Bands corresponding to the iron oxyhydroxide product did not shift. These results indicate water as the primary source of oxygen in the sulfate product, while the oxygen atoms in the iron oxyhydroxide product are obtained from dissolved molecular oxygen.
ISSN:0013-936X
1520-5851
DOI:10.1021/es0494003