Redox properties of structural Fe in clay minerals. 2. Electrochemical and spectroscopic characterization of electron transfer irreversibility in ferruginous smectite, SWa-1

Christopher Aaron Gorski, Laura Klüpfel, Andreas Voegelin, Michael Sander, Thomas B. Hofstetter

Research output: Contribution to journalArticle

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Abstract

Structural Fe in clay minerals is an important, albeit poorly characterized, redox-active phase found in many natural and engineered environments. This work develops an experimental approach to directly assess the redox properties of a natural Fe-bearing smectite (ferruginous smectite, SWa-1, 12.6 wt % Fe) with mediated electrochemical reduction (MER) and oxidation (MEO). By utilizing a suite of one-electron-transfer mediating compounds to facilitate electron transfer between structural Fe in SWa-1 and a working electrode, we show that the Fe2+/Fe3+ couple in SWa-1 is redox-active over a large range of potentials (from EH = -0.63 V to +0.61 V vs SHE). Electrochemical and spectroscopic analyses of SWa-1 samples that were subject to reduction and re-oxidation cycling revealed both reversible and irreversible structural Fe rearrangements that altered the observed apparent standard reduction potential (EH φ) of structural Fe. EH φ-values vary by as much as 0.56 V between SWa-1 samples with different redox histories. The wide range of E H-values over which SWa-1 is redox-active and redox history-dependent EH φ-values underscore the importance of Fe-bearing clay minerals as redox-active phases in a wide range of redox regimes.

Original languageEnglish (US)
Pages (from-to)9369-9377
Number of pages9
JournalEnvironmental Science and Technology
Volume46
Issue number17
DOIs
StatePublished - Sep 4 2012

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Clay minerals
smectite
clay mineral
electron
Electrons
oxidation
Bearings (structural)
history
electrode
Oxidation
Oxidation-Reduction
Smectite
Electrodes

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

Cite this

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Redox properties of structural Fe in clay minerals. 2. Electrochemical and spectroscopic characterization of electron transfer irreversibility in ferruginous smectite, SWa-1. / Gorski, Christopher Aaron; Klüpfel, Laura; Voegelin, Andreas; Sander, Michael; Hofstetter, Thomas B.

In: Environmental Science and Technology, Vol. 46, No. 17, 04.09.2012, p. 9369-9377.

Research output: Contribution to journalArticle

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