Iron Atom Exchange between Hematite and Aqueous Fe(II)

Andrew J Frierdich; Maria Helgeson; Chengshuai Liu; Chongmin Wang; Kevin M Rosso; Michelle M Scherer

doi:10.1021/acs.est.5b01276

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Iron Atom Exchange between Hematite and Aqueous Fe(II)

Journal article

Peer reviewed

Iron Atom Exchange between Hematite and Aqueous Fe(II)

Andrew J Frierdich, Maria Helgeson, Chengshuai Liu, Chongmin Wang, Kevin M Rosso and Michelle M Scherer

Environmental science & technology, Vol.49(14), pp.8479-8486

07/21/2015

DOI: 10.1021/acs.est.5b01276

PMID: 26069932

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https://www.osti.gov/servlets/purl/2217527View

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Abstract

Aqueous Fe(II) has been shown to exchange with structural Fe(III) in goethite without any significant phase transformation. It remains unclear, however, whether aqueous Fe(II) undergoes similar exchange reactions with structural Fe(III) in hematite, a ubiquitous iron oxide mineral. Here, we use an enriched (57)Fe tracer to show that aqueous Fe(II) exchanges with structural Fe(III) in hematite at room temperature, and that the amount of exchange is influenced by particle size, pH, and Fe(II) concentration. Reaction of 80 nm-hematite (27 m(2) g(-1)) with aqueous Fe(II) at pH 7.0 for 30 days results in ∼5% of its structural Fe(III) atoms exchanging with Fe(II) in solution, which equates to about one surface iron layer. Smaller, 50 nm-hematite particles (54 m(2) g(-1)) undergo about 25% exchange (∼3× surface iron) with aqueous Fe(II), demonstrating that structural Fe(III) in hematite is accessible to the fluid in the presence of Fe(II). The extent of exchange in hematite increases with pH up to 7.5 and then begins to decrease as the pH progresses to 8.0, likely due to surface site saturation by sorbed Fe(II). Similarly, when we vary the initial amount of added Fe(II), we observe decreasing amounts of exchange when aqueous Fe(II) is increased beyond surface saturation. This work shows that Fe(II) can catalyze iron atom exchange between bulk hematite and aqueous Fe(II), despite hematite being the most thermodynamically stable iron oxide.

Catalysis

Ferric Compounds - chemistry

Ferrous Compounds - chemistry

Hydrogen-Ion Concentration

Iron - chemistry

Particle Size

Solutions - chemistry

Thermodynamics

Water - chemistry

Details

Title: Subtitle: Iron Atom Exchange between Hematite and Aqueous Fe(II)
Creators: Andrew J Frierdich - University of Iowa
Maria Helgeson - University of Iowa
Chengshuai Liu - ECO (Czechia)
Chongmin Wang - Pacific Northwest National Laboratory
Kevin M Rosso - Pacific Northwest National Laboratory
Michelle M Scherer - University of Iowa
Resource Type: Journal article
Publication Details: Environmental science & technology, Vol.49(14), pp.8479-8486
DOI: 10.1021/acs.est.5b01276
PMID: 26069932
NLM abbreviation: Environ Sci Technol
ISSN: 0013-936X
eISSN: 1520-5851
Grant note: DOI: 10.13039/100000160, name: Division of Earth Sciences, award: 1347848; DOI: 10.13039/100006151, name: Basic Energy Sciences
Language: English
Date published: 07/21/2015
Academic Unit: Civil and Environmental Engineering
Record Identifier: 9984197098502771

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