Spectroscopic evidence for interfacial Fe(II)-Fe(III) electron transfer in a clay mineral

Michael V. Schaefer, Christopher A. Gorski, Michelle M. Scherer

Research output: Contribution to journalArticle

88 Scopus citations

Abstract

Interfacial electron transfer has been shown to occur between sorbed Fe(II) and structural Fe(III) in Fe oxides, but it is unknown whether a similar reaction occurs between sorbed Fe(II) and Fe(III)-bearing clay minerals. Here, we used the isotopic specificity of 57Fe Mössbauer spectroscopy to demonstrate electron transfer between sorbed Fe(II) and structural Fe(III) in an Fe-bearing smectite clay mineral (NAu-2, nontronite). Mössbauer spectra of NAu-2 reacted with aqueous 56Fe(II) (which is invisible to 57Fe Mössbauer spectroscopy) showed direct evidence for reduction of NAu-2 by sorbed Fe(II). Mössbauer spectra using aqueous 57Fe(II) showed that sorbed Fe(II) is oxidized upon sorption to the clay and pXRD patterns indicate that the oxidation product is lepidocrocite. Spectra collected at different temperatures indicate that reduction of structural Fe(III) by sorbed Fe(II) induces electron delocalization in the clay structure. Our results also imply that interpretation of room temperature and 77 K Mössbauer spectra may significantly underestimate the amount of Fe(II) in Fe-bearing clays. These findings provide compelling evidence for abiotic reduction of Fe-bearing clay minerals by sorbed Fe(II), and require us to reframe our conceptual model for interpreting biological reduction of clay minerals, as well as contaminant reduction by reduced clays.

Original languageEnglish (US)
Pages (from-to)540-545
Number of pages6
JournalEnvironmental Science and Technology
Volume45
Issue number2
DOIs
StatePublished - Jan 15 2011

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

Fingerprint Dive into the research topics of 'Spectroscopic evidence for interfacial Fe(II)-Fe(III) electron transfer in a clay mineral'. Together they form a unique fingerprint.

  • Cite this