Pyrite (FeS2) oxidation: A sub-micron synchrotron investigation of the initial steps

Chandra, Anand P.; Gerson, Andrea R.

doi:10.1016/j.gca.2011.08.005

Cited by 61 publications

(28 citation statements)

References 52 publications

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“…The oxidation of organic matter within the water column and on the sea floor can reduce sedimentary Br / Cl values. The pyrite in sediments can be oxidized to iron oxides and/or to hydroxides when it is in contact with dissolved oxygen (Chandra and Gerson, 2011). If these oxides and/or hydroxides are again reduced in sediments, Fe and As associated with pyrite would be released to pore water.…”

Section: 2)mentioning

confidence: 99%

Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition

et al. 2015

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Abstract. Holocene eastern Mediterranean Sea sediments contain an organic-rich sapropel S1 layer that was formed in oxygen-depleted waters. The spatial distribution of this layer revealed that during S1 deposition, deep waters were anoxic below a depth of 1800 m. However, whether this boundary permanently existed from the early to the mid-Holocene has not been examined yet. To answer this question, a multiproxy approach was applied to a core retrieved close to the 1800 m boundary (at 1780 m). We measured the bulk sediment elemental composition, the stable isotopic composition of the planktonic foraminifer Globigerinoides ruber and the abundance of benthic foraminifera since the last deglaciation. The result indicates that authigenic U and Mo accumulation began around 13-12 cal ka BP, in concert with surface water freshening estimated from the G. ruber δ 18 O record. The onset of bottom and pore water oxygen depletion occurred prior to S1 deposition inferred from barium enrichment. In the middle of the S1 deposition period, reduced authigenic V, Fe and As contents and the Br / Cl ratio indicated short-term bottom-water re-oxygenation. A sharp Mn peak and maximal abundance for benthic foraminifera marked a total recovery for circulation at approximately 7 cal ka BP. Based on our results and existing data, we suggest that S1 formation within the upper 1780 m of the eastern Mediterranean Sea was preconditioned by reduced ventilation, resulting from excess freshwater inputs due to insolation changes under deglacial conditions that initiated between 15 and 12 cal ka BP within the upper 1780 m. Short-term re-oxygenation in the Levantine Basin is estimated to have affected bottom water at least as deep as 1780 m in response to cooling and/or the reduction of freshwater inputs. We tentatively propose that complete ventilation recovery at the S1 termination was depth-dependent, with earlier oxygenation within the upper 1780 m. Our results provide new constraints on vertical water column structure in the eastern Mediterranean Sea since the last deglaciation.

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Section: 2)mentioning

confidence: 99%

Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition

et al. 2015

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“…It is known from X-ray photoelectron spectroscopy (XPS) and other surface-sensitive techniques [2][3][4][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] that iron can be easily released from the lattice of these compounds, leaving non-equilibrium metal-deficient surface layers. The resulting surface sulfur enrichment is generally modest for oxidation-resistant pyrite, with intrinsic (fractured) pyrite surfaces possibly even being S-deficient [2][3][4][5][6][17][18][19][20][21][22][23][24][25][26]. In contrast, the metal depleted layer incorporates di-and polysulfide species and low-spin Fe(II) and can be as thick as several micrometers at pyrrhotite reacted in acidic solutions under certain conditions [27][28][29][30][31][32][33][34]…”

Section: Introductionmentioning

confidence: 99%

Hard X-ray photoelectron and X-ray absorption spectroscopy characterization of oxidized surfaces of iron sulfides

Mikhlin

Tomashevich

Vorobyev

et al. 2016

Applied Surface Science

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a b s t r a c tHard X-ray photoelectron spectroscopy (HAXPES) using an excitation energy range of 2 keV to 6 keV in combination with Fe K-and S K-edge XANES, measured simultaneously in total electron (TEY) and partial fluorescence yield (PFY) modes, have been applied to study near-surface regions of natural polycrystalline pyrite FeS 2 and pyrrhotite Fe 1−x S before and after etching treatments in an acidic ferric chloride solution. It was found that the following near-surface regions are formed owing to the preferential release of iron from oxidized metal sulfide lattices: (i) a thin, no more than 1-4 nm in depth, outer layer containing polysulfide species, (ii) a layer exhibiting less pronounced stoichiometry deviations and low, if any, concentrations of polysulfide, the composition and dimensions of which vary for pyrite and pyrrhotite and depend on the chemical treatment, and (iii) an extended almost stoichiometric underlayer yielding modified TEY XANES spectra, probably, due to a higher content of defects. We suggest that the extended layered structure should heavily affect the near-surface electronic properties, and processes involving the surface and interfacial charge transfer.

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“…[2][3][4][5][6][7] Oxidation of pyrite present in minerals and coal during combustion processes in various industrial fields such as metallurgical processing, cement production or power production leads to harmful SO 2 emission. 8 A thorough understanding of the kinetics and themodynamics of pyrite oxidation is necessary to interpret and predict the decomposition and oxidation transformation of pyrite under different reaction conditions in industrial processes.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6][7]11,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Atmospheric oxidation has been mostly studied by synchrotron and conventional XPS, 3,4,7,11,13-24 but IR, 6 UPS, 5,13 SEM 24 and STM 5 have also been applied to identify surface oxidation products. Very few theoretical studies have been devoted to obtain atomic level understanding of the interaction of O 2 with FeS 2 surfaces.…”

Section: Introductionmentioning

confidence: 99%

DFT Study of Oxidation States on Pyrite Surface Sites

Rozgonyi

Stirling

2015

J. Phys. Chem. C

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Density functional calculations have been performed to study the interaction of oxygen with clean and defective pyrite (100) surfaces. Molecular adsorption states are predicted to undergo dissociation because atomic chemisorption is far more favorable thermodynamically for all surfaces. On the defect-free FeS2 surface molecular adsorption takes place on neighboring iron sites in a side-on fashion. S-adatoms react weakly with O2 whereas S-vacancies bind very strongly molecular oxygen. Dissociative chemisorption on clean surface prefers the sulfur atoms to iron in sharp contrast to water adsorption. Reaction with atomic oxygen is thermodynamically preferred on the defect sites when they are available. Oxidation can fully eliminate the S-adatom sites by SO2 formation. The most favorable sites for oxidation are sulfur vacancies where O atoms can occupy the missing sulfur sites. The predicted oxidation states and their relative stabilities are in agreement with experiments and expected to assist the interpretation of XPS measurements.

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Pyrite (FeS2) oxidation: A sub-micron synchrotron investigation of the initial steps

Cited by 61 publications

References 52 publications

Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition

Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition

Hard X-ray photoelectron and X-ray absorption spectroscopy characterization of oxidized surfaces of iron sulfides

DFT Study of Oxidation States on Pyrite Surface Sites

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