Fe(II)–Fe(III) Electron Transfer in a Clay Mineral with Low Fe Content

Latta, Drew E.; Neumann, Anke; Premaratne, W.A.P.J.; Scherer, Michelle M.

doi:10.1021/acsearthspacechem.7b00013

Cited by 64 publications

(60 citation statements)

References 79 publications

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“…The data also indicated an increase in the amount of para-Fe(II) of 60 mmol Fe •kg −1 , which is consistent with the observed increase in total Fe of 40-50 mmol Fe •kg −1 . In this case, the observed changes in Fe speciation and content (along with the blue color) are explained by the presence of additional Fe 2+ from the corroding heater, which can be attributed to ferrous hydroxide, sorbed Fe 2+ , and/or sorbed Fe 3+ following sorption of Fe 2+ and reduction of clay structural Fe 3+ (Gehin et al 2007;Soltermann et al 2013;Latta et al 2017). Data collected from sample OB11 (59 mm from the interface, at the transition between the orange and blue zones) indicated an increase in total Fe of 45 mmol Fe •kg −1 relative to the outermost samples, similar to that in previous samples B15 and B20.…”

Section: Febex Samplesmentioning

confidence: 88%

“…Fe 2+ diffusion into bentonite is generally considered to occur during the anaerobic period and will mainly interact with the bentonite medium through ion exchange on basal surfaces (Xia et al 2005;Wilson et al 2015) and sorption to edge sites (Gehin et al 2007;Soltermann et al 2013;Muurinen et al 2014;Latta et al 2017). A monophasic diffusion of Fe 2+ could, therefore, be expected.…”

Section: A Phenomenological Description Of the Fe Diffusion Mechanismmentioning

confidence: 99%

“…This Fe is considered to be immobile but can undergo reversible redox reactions with the diffusing Fe 2+ , through the reduction by Fe 2+ sorbed on the Fig. 11 Proposed Fe diffusion mechanism at the steel-bentonite interface edges (Schaefer et al 2011;Soltermann et al 2013Soltermann et al , 2014, and also on basal surfaces (Komadel et al 2006;Latta et al 2017). Moreover, sorption of diffusing Fe 2+ on pre-existing Fe 3+ bearing oxides (e.g.…”

Section: A Phenomenological Description Of the Fe Diffusion Mechanismmentioning

confidence: 99%

“…Most studies have been dedicated to small-scale laboratory systems, often designed to enhance Fe-clay interactions. Several corrosion-related processes affecting the barrier function of the bentonite backfill have been recognized, including (1) local cementation of bentonite via precipitation of Fe(II)/(III) (oxyhydr)oxides (Carlson et al 2007), (2) smectite dissolution via pH increase (Marty et al 2010), (3) destabilization of the dioctahedral smectite structure (Lantenois et al 2005) or (4) transformation of smectite to a non-swelling Fe phyllosilicate such as berthierine, cronstedtite, or odinite, by incorporation of diffusing Fe into the structure (Mosser-Ruck et al 2010;Kaufhold et al 2015), and (5) sorption of Fe on smectite, possibly followed by reduction of smectite structural Fe (Gehin et al 2007;Soltermann et al 2013;Latta et al 2017) leading to changes of clay properties such as cationexchange capacity (CEC) or hydration . In turn, the properties of bentonite also seem to have an influence on the corrosion process (Kaufhold et al 2015).…”

Section: Introductionmentioning

confidence: 99%

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Eighteen years of steel–bentonite interaction in the FEBEX in situ test at the Grimsel Test Site in Switzerland

Hadi

Wersin

Serneels

et al. 2019

Clays and clay miner.

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Corrosion of steel canisters containing buried high-level radioactive waste is a relevant issue for the long-term integrity of repositories. The purpose of the present study was to evaluate this issue by examining two differently corroded blocks originating from a full-scale in situ test of the FEBEX bentonite site in Switzerland. The FEBEX experiment was designed initially as a feasibility test of an engineered clay barrier system and was recently dismantled after 18 years of activity. Samples were studied by Fspatially resolved`and Fbulk`experimental methods, including Scanning Electron Microscopy, Elemental Energy Dispersive Spectroscopy (SEM-EDX), μ-Raman spectroscopy, X-ray Fluorescence (XRF), X-ray Diffraction (XRD), and 57 Fe Mössbauer spectrometry, with a focus on Fe-bearing phases. In one of the blocks, corrosion of the steel liner led to diffusion of Fe into the bentonite, resulting in the formation of large (width > 140 mm) red, orange, and blue colored halos. Goethite was identified as the main corrosion product in the red and orange zones while no excess Fe 2+ (compared to the unaffected bentonite) was observed there. Excess Fe 2+ was found to have diffused further into the clay (in the blue zones) but its speciation could not be unambiguously clarified. The results indicate the occurrence of newly formed octahedral Fe 2+ either as Fe 2+ sorbed on the clay or as structural Fe 2+ inside the clay (following electron transfer from sorbed Fe 2+). No other indications of clay transformation or newly formed clay phases were found. The overall pattern indicates that diffusion of Fe was initiated when oxidizing conditions were still prevailing inside the bentonite block, resulting in the accumulation of Fe 3+ close to the interface (up to three times the original Fe content), and continued when reducing conditions were reached, allowing deeper diffusion of Fe 2+ into the clay (inducing an increase of 10-12% of the Fe content).

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Section: Febex Samplesmentioning

confidence: 88%

Section: A Phenomenological Description Of the Fe Diffusion Mechanismmentioning

confidence: 99%

Section: A Phenomenological Description Of the Fe Diffusion Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Eighteen years of steel–bentonite interaction in the FEBEX in situ test at the Grimsel Test Site in Switzerland

Hadi

Wersin

Serneels

et al. 2019

Clays and clay miner.

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“…1,2 Over the last decade significant evidence has accumulated to demonstrate interfacial electron transfer between sorbed Fe(II) and Fe(III) in Fe oxides and Fe-containing clay minerals. [3][4][5][6][7][8][9][10][11][12][13][14][15] In some cases, electron transfer also appears to be followed by mixing of Fe atoms from the bulk mineral structure with the surrounding fluid (also termed Fe(II)-catalyzed recrystallization). 10,[16][17][18][19][20][21][22][23] While Fe(II)-Fe(III) electron transfer and mixing have been clearly demonstrated, a mechanistic understanding of these reactions remains elusive.…”

Section: Introductionmentioning

confidence: 99%

The Role of Defects in Fe(II)–Goethite Electron Transfer

Notini

Latta

Neumann

et al. 2018

Environ. Sci. Technol.

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Despite substantial experimental evidence for Fe(II)-Fe(III) oxide electron transfer, computational chemistry calculations suggest that oxidation of sorbed Fe(II) by goethite is kinetically inhibited on structurally perfect surfaces. We used a combination of Fe Mössbauer spectroscopy, synchrotron X-ray absorption and magnetic circular dichroism (XAS/XMCD) spectroscopies to investigate whether Fe(II)-goethite electron transfer is influenced by defects. Specifically, Fe L-edge and O K-edge XAS indicates that the outermost few Angstroms of goethite synthesized by low temperature Fe(III) hydrolysis is iron deficient relative to oxygen, suggesting the presence of defects from Fe vacancies. This nonstoichiometric goethite undergoes facile Fe(II)-Fe(III) oxide electron transfer, depositing additional goethite consistent with experimental precedent. Hydrothermal treatment of this goethite, however, appears to remove defects, decrease the amount of Fe(II) oxidation, and change the composition of the oxidation product. When hydrothermally treated goethite was ground, surface defect characteristics as well as the extent of electron transfer were largely restored. Our findings suggest that surface defects play a commanding role in Fe(II)-goethite redox interaction, as predicted by computational chemistry. Moreover, it suggests that, in the environment, the extent of this interaction will vary depending on diagenetic history, local redox conditions, as well as being subject to regeneration via seasonal fluctuations.

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Unravelling the corrosion processes at steel/bentonite interfaces in in situ tests

Wersin

Hadi

Kiczka

et al. 2023

Materials & Corrosion

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Microscopic and spectroscopic analyses were conducted on steel/bentonite interface samples removed from four in situ experiments that were carried out in three underground research laboratories at different temperatures and under different hydraulic and geochemical conditions. The results provide valuable information about the corrosion processes occurring in high‐level radioactive waste repositories. Systematic patterns can be deduced from the results, irrespective of carbon steel grade, type of bentonite and its degree of compaction, geochemical environment or experimental setup. Thus, a clear dependence of the corrosion rates on temperature and exposure period, as well as on the availability of H2O and O2 provided by the surrounding bentonite buffer, is observed. Furthermore, Fe(II) ions released by corrosion interact with the structural Fe in the clay. Recent developments highlight the usefulness of reactive transport modelling in understanding the coupled corrosion and Fe–clay interaction processes.

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Fe(II)–Fe(III) Electron Transfer in a Clay Mineral with Low Fe Content

Abstract: Newcastle University ePrints -eprint.ncl.ac.uk Latta DE, Neumann A, Premaratne WAPJ, Scherer MM. Fe(II) -Fe(III) electron transfer in a clay mineral with low Fe content. Earth and Space Chemistry 2017, http://doi.

Cited by 64 publications

References 79 publications

Eighteen years of steel–bentonite interaction in the FEBEX in situ test at the Grimsel Test Site in Switzerland

Eighteen years of steel–bentonite interaction in the FEBEX in situ test at the Grimsel Test Site in Switzerland

The Role of Defects in Fe(II)–Goethite Electron Transfer

Unravelling the corrosion processes at steel/bentonite interfaces in in situ tests

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