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Aqueous pyrite oxidation by dissolved oxygen and by ferric iron

June 1, 1987

Rates of aqueous, abiotic pyrite oxidation were measured in oxygen-saturated and anaerobic Fe(III)-saturated solutions with initial pH from 2 to 9. These studies included analyses of sulfite, thiosulfate, polythionates and sulfate and procedures for cleaning oxidation products from pyrite surfaces were evaluated. Pyrite oxidation in oxygen-saturated solutions produced (1) rates that were only slightly dependent on initial pH, (2) linear increases in sulfoxy anions and (3) thiosulfate and polythionates at pH > 3.9. Intermediate sulfoxy anions were observed only at high stirring rates. In anaerobic Fe(III)-saturated solutions, no intermediates were observed except traces of sulfite at pH 9. The faster rate of oxidation in Fe(III)-saturated solutions supports a reaction mechanism in which Fe(III) is the direct oxidant of pyrite in both aerobic and anaerobic systems. The proposal of this mechanism is also supported by theoretical considerations regarding the low probability of a direct reaction between paramagnetic molecular oxygen and diamagnetic pyrite. Results from a study of sphalerite oxidation support the hypothesis that thiosulfate is a key intermediate in sulfate production, regardless of the bonding structure of the sulfide mineral.

Publication Year 1987
Title Aqueous pyrite oxidation by dissolved oxygen and by ferric iron
DOI 10.1016/0016-7037(87)90337-1
Authors Carl O. Moses, D. Kirk Nordstrom, Janet S. Herman, Aaron L. Mills
Publication Type Article
Publication Subtype Journal Article
Series Title Geochimica et Cosmochimica Acta
Index ID 70185544
Record Source USGS Publications Warehouse
USGS Organization Toxic Substances Hydrology Program
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