期刊
ACS EARTH AND SPACE CHEMISTRY
卷 3, 期 12, 页码 2717-2725出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsearthspacechem.9b00224
关键词
Electron transfer; Fe(III) oxide; reductive dissolution; Fe oxide recrystallization; ETAS
资金
- U.S. Department of Energy's (DOE) Office of Science, Office of Basic Energy Sciences (BES), Chemical Sciences, Geosciences, and Biosciences Division through its Geosciences program at Pacific Northwest National Laboratory (PNNL)
- DOE Office of Biological and Environmental Research and located at PNNL
- Office of Science, BES of the DOE [DE-AC02-05CH11231]
- DOE, Battelle Memorial Institute [DE-AC05-76RL01830]
- National Science Foundation (NSF) through the NSF Division of Chemistry [1708467]
- NSF Division of Graduate Education [1633098]
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1708467] Funding Source: National Science Foundation
- Division Of Graduate Education
- Direct For Education and Human Resources [1633098] Funding Source: National Science Foundation
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 Fe-57 Mossbauer 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.
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