A vibrational spectroscopic 18O tracer study of pyrite oxidation

Sulfate: A time capsule for Earth's O2, O3, and H2O

“…The final O 2 fraction in sulfate oxygen appears to be determined by competing oxidation rates of the Fe (III) and O 2 pathways as well as the rate of sulfite (SO 3 2 − )-water oxygen exchange. The retaining of O 2 signature in sulfite and sulfate sourced from pyrite oxidation seems to be in contrast to results from spectroscopic experiments (Reedy et al, 1991;Usher et al, 2004) that support an absence of dissolved O 2 signal in sulfate formed by pyrite oxidation. It is also inconsistent with the "semiconductor" model for pyrite oxidation which advocates that nucleophilic attack of water hydroxyls on the sulfur side results in the incorporation of water oxygen in sulfoxyanions all the way to sulfate (Rimstidt and Vaughan, 2003).…”

The effect of As, Co, and Ni impurities on pyrite oxidation kinetics: An electrochemical study of synthetic pyrite

“…This could be because the majority carriers for As-doped pyrite tend to be holes (Table 1). Holes travel by eventually displacing electrons; as they reach the pyrite surface they eventually displace the bonding electrons, thereby oxidizing S and enhancing the forced injection of holes at 1.1 V. The partially oxidized sulfur ions are thought to react with H 2 O (Reedy et al, 1991) and are eventually released as sulfate into solution along with ferrous iron (Reaction (3)). The potential step measurements used to define the Tafel slopes are collected at more modest potentials, 0.65-0.4 V, where the anodic dissolution (Reaction (3)) occurs (Holmes and Crundwell, 2000) without electrochemically forced production of holes.…”

O and S isotopic composition of dissolved and attached oxidation products of pyrite by Acidithiobacillus ferrooxidans: Comparison with abiotic oxidations

“…The sulphur and oxygen isotopic compositions of dissolved sulphates produced during the oxidation of pyrite have been studied for the different oxidation mechanisms (Suzuki, 1965;Toran and Harris, 1989;Reedy et al, 1991). Because oxygen isotopic exchanges between dissolved sulphates and water is slow even at low pH (Chiba and Sakai, 1985), the d 18 O of sulphates formed during bio-or chemo-oxidation of pyrite are a reliable proxy for the oxidation mechanisms.…”

“…The rate of reaction (2), which is supposed to be the dominant one (Reedy et al, 1991), depends on the availability of Fe 3+ which is controlled by:…”