Characterization and crystal chemistry of an Fe-rich montmorillonite from Ölberg, Germany

Petit, Sabine; Caillaud, Jacinthe; Righi, D.; Madejová, Jana; Elsass, Françoise; Köster, Heinrich M.

doi:10.1180/0009855023720034

Cited by 61 publications

(51 citation statements)

References 23 publications

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“…Because all three bands decreased in intensity in the spectrum of reduced Ö lberg montmorillonite (G, 88% Fe(II)/total Fe), all three bands are associated with Fe(III). Hence, the bands were assigned to AlFe(III)-OH (867 cm À1 ), Fe(III)Fe(III)-OH (818 cm À1 ), and MgFe(III)-OH groups (759 cm À1 ), in agreement with a previous study (Petit et al, 2002). A schematic representation of the octahedral structure of unaltered Ö lberg montmorillonite is given in Fig.…”

Section: Fe(ii) Species In ö Lberg Montmorillonitementioning

confidence: 87%

“…Ferruginous smectite (SWa-1) and Wyoming montmorillonite (SWy-2) were obtained from the Source Clays Repository (Columbia, Missouri), fractioned to <2 lm, and freeze-dried prior to use. Ö lberg montmorillonite (iron-rich montmorillonite from Ö lberg (Petit et al, 2002), <2 lm fraction) and synthetic nontronite (Decarreau et al, 2008) were used as obtained.…”

Section: Clay Mineral Reduction and Re-oxidationmentioning

confidence: 99%

“…b Determined as described in (Hofstetter et al, 2006). c R þ 0:38 ðSi 7:98 Al 0:02 ÞðFeðIIIÞ 2:22 Mg 1:72 Al 0:48 ÞO 20 ðOHÞ 4 taken from (Petit et al, 2002). d Determined according to a modified 1,10-phenanthroline method (Stucki, 1981;Amonette and Templeton, 1998).…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of redox-active iron sites in smectites using middle and near infrared spectroscopy

Neumann

Petit

Hofstetter

2011

Geochimica et Cosmochimica Acta

110

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Redox processes of structural Fe in clay minerals play an important role in biogeochemical cycles and for the dynamics of contaminant transformation in soils and aquifers. Reactions of Fe(II)/Fe(III) in clay minerals depend on a variety of mineralogical and environmental factors, which make the assessment of Fe redox reactivity challenging. Here, we use middle and near infrared (IR) spectroscopy to identify reactive structural Fe(II) arrangements in four smectites that differ in total Fe content, octahedral cationic composition, location of the negative excess charge, and configuration of octahedral hydroxyl groups. Additionally, we investigated the mineral properties responsible for the reversibility of structural alterations during Fe reduction and re-oxidation. For Wyoming montmorillonite (SWy-2), a smectite of low structural Fe content (2.8 wt%), we identified octahedral AlFe(II)-OH as the only reactive Fe(II) species, while high structural Fe content (>12 wt%) was prerequisite for the formation of multiple Fe(II)-entities (dioctahedral AlFe(II)-OH, MgFe(II)-OH, Fe(II)Fe(II)-OH, and trioctahedral Fe(II)Fe(II)Fe(II)-OH) in iron-rich smectites Ö lberg montmorillonite, and ferruginous smectite (SWa-1), as well as in synthetic nontronite. Depending on the overall cationic composition and the location of excess charge, different reactive Fe(II) species formed during Fe reduction in iron-rich smectites, including tetrahedral Fe(II) groups in synthetic nontronite. Trioctahedral Fe(II) domains were found in tetrahedrally charged ferruginous smectite and synthetic nontronite in their reduced state while these Fe(II) entities were absent in Ö lberg montmorillonite, which exhibits an octahedral layer charge. Fe(III) reduction in iron-rich smectites was accompanied by intense dehydroxylation and structural rearrangements, which were only partially reversible through re-oxidation. Re-oxidation of Wyoming montmorillonite, in contrast, restored the original mineral structure. Fe(II) oxidation experiments with nitroaromatic compounds as reactive probes were used to link our spectroscopic evidence to the apparent reactivity of structural Fe(II) in a generalized kinetic model, which takes into account the presence of Fe(II) entities of distinctly different reactivity as well as the dynamics of Fe(II) rearrangements.

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Section: Fe(ii) Species In ö Lberg Montmorillonitementioning

confidence: 87%

Section: Clay Mineral Reduction and Re-oxidationmentioning

confidence: 99%

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Evaluation of redox-active iron sites in smectites using middle and near infrared spectroscopy

Neumann

Petit

Hofstetter

2011

Geochimica et Cosmochimica Acta

110

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“…3, Table 3). The band near 4375 cm − 1 is the major band of sample (0) which contains only Fe 3+ as octahedral cation and was then attributed to Fe 3+ 2 -OH combination (Bishop et al, 1999;Petit et al, 2002;Gates, 2005;Decarreau et al, 2008;Andrieux and Petit, 2010;Neumann et al, 2011). Indeed, this band results clearly from the combination of νFe 3+ 2 -OH (stretching -3565 cm − 1 ) and δ Fe 3+ 2 -OH (bending -813 cm −1 ) observed in MIR (see below).…”

Section: Nir (ν + δ) Oh Combination Bandsmentioning

confidence: 98%

Hydrothermal synthesis of dioctahedral smectites: The Al–Fe3+ chemical series. Part II: Crystal-chemistry

Petit

Decarreau

Gates

et al. 2015

Applied Clay Science

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“…vibrations indicating an Fe-rich smectite while the second is typically due to water (Petit et al, 2002). A strong Si-O stretching band appears at 1021 cm-l .…”

Section: Infrared Spectral Analysismentioning

confidence: 99%

Formation of Nontronite from Oxidative Dissolution of Pyrite Disseminated in Precambrian Felsic Metavolcanics of the Southern Iberian Massif (spain)

Fernández-Caliani¹,

Crespo²,

Rodas³

et al. 2004

Clays Clay Miner.

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Abstract-This paper describes a rare occurrence of nontronite associated with sulfide-bearing felsic metavolcanics, providing evidence of colloidal deposition in open spaces as result of a low-temperature water-rock interaction. Microbotryoidal masses of green nontronite with impurities of kao linite, illite, barite, amorphous silica and iron oxyhydroxides are found as vein and cavity fillings in deeply kaolinized rhyolites and rhyolitic tuffs of Precambrian age, at Oliva de Merida in SW Spain. Clay mineral characterization has been carried out by X-ray diffraction, infrared spectroscopy, thermal analysis, analytical electron microscopy and stable isotope (oxygen and hydrogen) analysis. Nontronite was formed under low-temperature alteration conditions, from a continuous sequence of reactions and aqueous solution compositions, involving two basic processes that acted in concert: oxidative dissolution of pyrite and hydrolysis of K-feldspar. After acidity neutralization, dissolved silica released by incongruent dissolution of K-feldspar reacted with ferric sulfate derived from pyrite oxidation to form nontronite under oxidizing conditions, in the presence of relatively warm meteoric water.

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Characterization and crystal chemistry of an Fe-rich montmorillonite from Ölberg, Germany

Cited by 61 publications

References 23 publications

Evaluation of redox-active iron sites in smectites using middle and near infrared spectroscopy

Evaluation of redox-active iron sites in smectites using middle and near infrared spectroscopy

Hydrothermal synthesis of dioctahedral smectites: The Al–Fe3+ chemical series. Part II: Crystal-chemistry

Formation of Nontronite from Oxidative Dissolution of Pyrite Disseminated in Precambrian Felsic Metavolcanics of the Southern Iberian Massif (spain)

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