Oxidation state and coordination of Fe in minerals: An Fe<i>K-</i>XANES spectroscopic study

Wilke, Max; Farges, François; Petit, P.; Brown, Gordon E.; Martin, F.

doi:10.2138/am-2001-5-612

Cited by 1,006 publications

(1,262 citation statements)

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“…2 shows the normalized XAFS and XANES (inset) spectra for bare and starch-stabilized Fe 3 O 4 particles. The peak at 7.112 keV is attributed to quadrupole transitions from the 1s to 3d orbitals (Wilke et al, 2001;Chen et al, 2002). The peak at 7.132 keV shows the d-p hybriding between the metal atoms and ligands through bonding and multiple scatterings involving the same atoms with different scattering paths (Ankudinov et al, 2000).…”

Section: Resultsmentioning

confidence: 99%

“…Synchrotron-based X-ray absorption spectroscopy is a widelyused technique for determining the local geometric and/or electronic structure of surface species (Waychunas et al, 1983;Peterson et al, 1997;Wilke et al, 2001;Morin et al, 2008;Missana et al, 2009;Wang et al, 2010). X-ray absorption near edge structure (XANES) is a powerful means to determine the overall oxidation state of iron, especially the pre-edge feature which is sensitive to Fe oxidation states (Waychunas et al, 1983).…”

Section: Introductionmentioning

confidence: 99%

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XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate

Zhang

Pan

Zhao

et al. 2011

Environmental Pollution

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a b s t r a c tIt has been shown that starch can effectively stabilize nanoscale magnetite particles, and starch-stabilized magnetite nanoparticles (SMNP) are promising for in situ remediation of arsenic-contaminated soils. However, a molecular level understanding has been lacking. Here, we carried out XAFS studies to bridge this knowledge gap. Fe K-edge XAFS spectra indicated that the FeeO and FeeFe coordination numbers of SMNP were lower than those for bare magnetite particles, and these coordination numbers decreased with increasing starch concentration. The decrease in the average coordination number at elevated stabilizer concentration was attributed to the increase in the surface-to-volume ratio. Arsenic K-edge XAFS spectra indicated that adsorbed arsenate on SMNP consisted primarily of binuclear bidentate (BB) complexes and monodentate mononuclear (MM) complexes. More BB complexes (energetically more favorable) were observed at higher starch concentrations, indicating that SMNP not only offered greater adsorption surface area, but also stronger adsorption affinity toward arsenate.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate

Zhang

Pan

Zhao

et al. 2011

Environmental Pollution

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“…2A), the pre-edge peak around 7110 eV is attributed to the quadrupole transition from 1s to 3d orbital [42,43]. The absorption K-edge at 7122 eV does not show any obvious energy shift, indicating that the substitution of Mn cations does not affect the valences of iron cations.…”

Section: Xafs Spectroscopymentioning

confidence: 96%

The distinct effects of Mn substitution on the reactivity of magnetite in heterogeneous Fenton reaction and Pb(II) adsorption

Liang

Zhu

Wei

et al. 2014

Journal of Colloid and Interface Science

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“…The contribution from components centered above 7115.0 eV was ignored. 22,23 The obtained centroid positions have been calibrated to the reported values of Wilke and co-workers, which results in a shift to lower energy of 0.77 eV. Figure 2 shows the pre-edge region of the Fe K-edge X-ray absorption spectrum of Fe 2 SiO 4 (fayalite) measured in two different ways.…”

Section: Data Processingmentioning

confidence: 98%

“…In a detailed and extensive XANES study on Fe-bearing minerals Wilke and co-workers 22 presented a correlation of the changes of the Fe K pre-edge with the oxidation state and local symmetry. The pre-edge features of Fe in more than 30 minerals and synthetic compounds were systematically studied.…”

Section: Introductionmentioning

confidence: 99%

Kβ-Detected XANES of Framework-Substituted FeZSM-5 Zeolites

et al. 2004

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The valence and local symmetry of iron in framework-substituted FeZSM-5 with a high Fe dilution (Si/Fe ) 360) was studied by means of K -detected X-ray absorption spectroscopy. This technique combines highresolution (∆E ∼1 eV) fluorescence detection of the 3p to 1s (K ) transition with the X-ray absorption near-edge structure (XANES) at the Fe K-edge. An absorption-like spectrum is recorded by detecting the K fluorescence intensity as a function of the incident energy that is scanned through the K absorption edge. K -detected XANES spectra allow for a more precise separation of the weak K pre-edge structure from the main edge as compared to conventional absorption spectroscopy. Subsequent analysis and interpretation of the pre-edge spectral features therefore is more accurate. The pre-edge is sensitive to changes in the local coordination and oxidation state of Fe. Using this technique we were able to quantitatively determine the degree of iron extraction out of a zeolite framework upon steaming. With the use of appropriate reference compounds, the pre-edge analysis was used to monitor the activation of low-loaded, framework-substituted FeZSM-5 (0.3 wt % Fe). Template removal and calcination distort the zeolite framework and induce a deviation from T d symmetry for incorporated iron. The (deliberate) presence of water at high temperature (T > 500°C) facilitates the hydrolysis of the Si-O-Fe bonds and increases the formation of extraframework iron species. The amount of Fe III occupying tetrahedral sites in the MFI-type zeolite decreases to 32% and 19%, respectively, for mild-and hard-steamed samples.

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Oxidation state and coordination of Fe in minerals: An FeK-XANES spectroscopic study

Cited by 1,006 publications

References 70 publications

XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate

XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate

The distinct effects of Mn substitution on the reactivity of magnetite in heterogeneous Fenton reaction and Pb(II) adsorption

Kβ-Detected XANES of Framework-Substituted FeZSM-5 Zeolites

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