Journal article
Atom Exchange between Aqueous Fe(II) and Structural Fe in Clay Minerals
Environmental science & technology, Vol.49(5), pp.2786-2795
03/03/2015
DOI: 10.1021/es504984q
PMID: 25671351
Abstract
Due to their stability toward reductive dissolution, Fe-bearing clay minerals are viewed as a renewable source of Fe redox activity in diverse environments. Recent findings of interfacial electron transfer between aqueous Fe(II) and structural Fe in clay minerals and electron conduction in octahedral sheets of nontronite, however, raise the question whether Fe interaction with clay minerals is more dynamic than previously thought. Here, we use an enriched isotope tracer approach to simultaneously trace Fe atom movement from the aqueous phase to the solid (57Fe) and from the solid into the aqueous phase (56Fe). Over 6 months, we observed a significant decrease in aqueous 57Fe isotope fraction, with a fast initial decrease which slowed after 3 days and stabilized after about 50 days. For the aqueous 56Fe isotope fraction, we observed a similar but opposite trend, indicating that Fe atom movement had occurred in both directions: from the aqueous phase into the solid and from the solid into aqueous phase. We calculated that 5–20% of structural Fe in clay minerals NAu–1, NAu–2, and SWa–1 exchanged with aqueous Fe(II), which significantly exceeds the Fe atom layer exposed directly to solution. Calculations based on electron-hopping rates in nontronite suggest that the bulk conduction mechanism previously demonstrated for hematite and suggested as an explanation for the significant Fe atom exchange observed in goethite may be a plausible mechanism for Fe atom exchange in Fe-bearing clay minerals. Our finding of 5–20% Fe atom exchange in clay minerals indicates that we need to rethink how Fe mobility affects the macroscopic properties of Fe-bearing phyllosilicates and its role in Fe biogeochemical cycling, as well as its use in a variety of engineered applications, such as landfill liners and nuclear repositories.
Details
- Title: Subtitle
- Atom Exchange between Aqueous Fe(II) and Structural Fe in Clay Minerals
- Creators
- Anke Neumann - University of IowaLingling Wu - University of IowaWeiqiang Li - University of Wisconsin–MadisonBrian L Beard - University of Wisconsin–MadisonClark M Johnson - University of Wisconsin–MadisonKevin M Rosso - Pacific Northwest National LaboratoryAndrew J Frierdich - University of IowaMichelle M Scherer - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Environmental science & technology, Vol.49(5), pp.2786-2795
- Publisher
- American Chemical Society
- DOI
- 10.1021/es504984q
- PMID
- 25671351
- ISSN
- 0013-936X
- eISSN
- 1520-5851
- Grant note
- DOI: 10.13039/501100001659, name: Deutsche Forschungsgemeinschaft, award: NE 1715/1-1; DOI: 10.13039/100006206, name: Biological and Environmental Research, award: DE-SC0006692; DOI: 10.13039/501100001711, name: Swiss National Science Foundation, award: PBEZP2 137292; DOI: 10.13039/100000160, name: Division of Earth Sciences, award: EAR-PF 1347848
- Language
- English
- Date published
- 03/03/2015
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984197260002771
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