X-ray photoelectron and Auger electron spectroscopic studies of pyrrhotite and mechanism of air oxidation

Pratt, Allen; Muir, I.J.; Nesbitt, H.W.

doi:10.1016/0016-7037(94)90508-8

Cited by 370 publications

(207 citation statements)

References 32 publications

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“…The S 2p binding energy is indicative of the type of sulfide present since FeS has a binding energy of 161.5 eV whereas in FeS 2 the binding energy shifts to 162.2 eV. [49][50][51] Thus, X-ray photoelectron spectroscopy also indicates the presence of FeS.…”

Section: Shown Inmentioning

confidence: 99%

Surface Chemistry and Extreme-Pressure Lubricant Properties of Dimethyl Disulfide

et al. 1998

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The growth kinetics of a film formed by the thermal decomposition of dimethyl disulfide on an iron foil are measured using a microbalance where the growth kinetics are parabolic (film thickness X varies with time as X 2 ∝ t) at high reaction temperatures and pressures, indicating that it is limited by diffusion through the film. The activation energy for this process is 54.5 ( 0.5 kcal/mol. The growth rate becomes linear as the reaction temperature and/or reactant pressure is lowered, indicating that, under these circumstances, the reaction rate is limited by thermal decomposition of dimethyl disulfide at the growing interface. The activation energy for thermal decomposition at the interface is found to be 37.6 ( 0.7 kcal/mol, and a half-order kinetics pressure dependence for the surface reaction rate is found consistent with a reaction limited by the rate of dimethyl disulfide dissociation. Analysis of the resulting film using Raman and X-ray photoelectron spectroscopies as well as X-ray diffraction reveal the formation of FeS, which may be slightly nonstoichiometric. This film is similar to that formed by methanethiol, suggesting that they may both initially form a surface thiolate species that further reacts to form FeS. The half-order reaction kinetics noted above are consistent with this. Measurement of dimethyl disulfide as an extreme-pressure (antiseizure) additive reveals a plateau at an applied load of ∼4000 N in the seizure load versus additive concentration curve. It has previously been suggested that the plateau corresponds to the load at which the interface reaches the melting point of the solid lubricant layer (in this case proposed to be FeS). Estimation of the interfacial temperature using a method developed previously yields an interfacial temperature of ∼1480 K, in good agreement with the melting point of FeS.

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Section: Shown Inmentioning

confidence: 99%

Surface Chemistry and Extreme-Pressure Lubricant Properties of Dimethyl Disulfide

et al. 1998

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“…The chemical reactivity of iron sulfides in the environment and during mineral processing, as well as their electronic and optical properties strongly depend on the composition and structure of the real surfaces formed in natural and technological environ-ments. 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].…”

Section: Introductionmentioning

confidence: 99%

“…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][35]; for example, Pratt and co-workers [30][31][32] have reported Auger depth profiles of several reacted pyrrhotites. It remains, however, unclear how the undersurface species alter with depth, in particular, because Ar + ion sputtering employed in many works could seriously affect the chemical state of Fe and S.…”

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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“…Pratt et al (1994) proposed a mechanism for pyrrhotite oxidation by which the only movement of species during the reaction was the transfer of electrons from the crystal lattice and the diffusion of iron towards the surface ferric oxyhyroxide layer. Pratt et al (1994) argued that the most reactive sites for oxygen reduction were associated with the ferric iron-sulfur bonds and the vacancies in the pyrrhotite crystal lattice. The presence of vacancies would therefore facilitate electron transfer as well as the diffusion of iron through the crystal lattice to the surface, thereby assisting the oxidation reaction.…”

Section: Crystallographymentioning

confidence: 99%

“…Fe 3+ was noted by Janzen (1996) to be a much stronger oxidising agent than O 2 . The presence of both Fe 2+ and Fe 3+ has been argued to be present in the pyrrhotite structure in order to maintain charge balance (Bertaut, 1953;Pratt et al, 1994;Mikhlin and Tomashevich, 2005). Therefore, magnetic pyrrhotite of formula Fe 3þ 2 Fe 2þ 5 S 2À 8 (Fe 7 S 8 ) contains proportionally more Fe 3+ in its structure than non-magnetic pyrrhotite of formula Fe 3þ 2 Fe 2þ 7 S 2À 10 (Fe 9 S 10 ).…”

Section: Mineral Chemistrymentioning

confidence: 99%

The flotation of magnetic and non-magnetic pyrrhotite from selected nickel ore deposits

Becker

Villiers

Bradshaw

2010

Minerals Engineering

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a b s t r a c tThe non-stoichiometric sulfide mineral pyrrhotite (Fe (1Àx) S), common to many nickel ore deposits, occurs in different crystallographic forms and compositions. A series of pyrrhotite samples derived from Canada, South Africa and Botswana whose mineralogy is well characterised, were selected here in order to develop the relationship between mineralogy and flotation performance. Using both oxygen uptake and microflotation tests, the behaviour of the different pyrrhotite types was compared in terms of the effect of pH and collector addition. Non-magnetic pyrrhotite was less reactive in terms of its oxygen uptake and showed the best collectorless flotation recovery. Magnetic pyrrhotite was more reactive and showed poor collectorless flotation performance that could be improved with the addition of xanthate collector, but only if it was not already passivated. These differences are interpreted to be a result of pyrrhotite mineralogy. This has implications that may aid the manipulation of pyrrhotite flotation performance in processing operations.

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X-ray photoelectron and Auger electron spectroscopic studies of pyrrhotite and mechanism of air oxidation

Cited by 370 publications

References 32 publications

Surface Chemistry and Extreme-Pressure Lubricant Properties of Dimethyl Disulfide

Surface Chemistry and Extreme-Pressure Lubricant Properties of Dimethyl Disulfide

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

The flotation of magnetic and non-magnetic pyrrhotite from selected nickel ore deposits

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