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A Closer Look at Fe(II) Passivation of Goethite

Lookup NU author(s): Dr Anke Neumann

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This is the authors' accepted manuscript of an article that has been published in its final definitive form by American Chemical Society, 2019.

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Abstract

Our understanding of how Fe(II) reacts with Fe(III) oxides has evolved based on evidence for electron transfer at the oxide–water interface and Fe(II)-catalyzed recrystallization. There is, however, some evidence that these, and other processes, such as microbial reduction, cease after continued contact with Fe(II) as the Fe oxide becomes “passivated”. Here, we explore the mechanism of oxide passivation by measuring whether exposure to Fe(II) inhibits Fe(II)–goethite electron transfer, and whether this inhibition is reversible. To quantify the extent of electron transfer, we used selective isotope labeling with 57Fe Mössbauer spectroscopy. We provide experimental evidence that pre-exposure to Fe(II) alters the products formed and inhibits the extent of electron transfer between goethite and Fe(II). We demonstrate that the goethite surface can accumulate a passivation layer of sorbed Fe(II) and that further electron transfer between Fe(II) and goethite is inhibited. Importantly, however, electron transfer can be partially restored upon removal of the layer of Fe(II) by extraction or oxidation. Our results suggest that in environments that are commonly subjected to transient geochemical fluctuations, electron transfer between Fe(II) and Fe oxides, and processes linked to it are likely to be relevant beyond just short time scales.


Publication metadata

Author(s): Notini L, Latta DE, Neumann A, Pearce CI, Sassi M, N'Diaye AT, Rosso KM, Scherer MM

Publication type: Article

Publication status: Published

Journal: ACS Earth and Space Chemistry

Year: 2019

Volume: 3

Issue: 12

Pages: 2717-2725

Print publication date: 19/12/2019

Online publication date: 28/10/2019

Acceptance date: 28/10/2019

Date deposited: 28/11/2019

ISSN (electronic): 2472-3452

Publisher: American Chemical Society

URL: https://doi.org/10.1021/acsearthspacechem.9b00224

DOI: 10.1021/acsearthspacechem.9b00224


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