The role of defects in Fe(II) – goethite electron transfer

Journal Article · Tue Mar 06 04:00:00 EST 2018 · Environmental Science & Technology

DOI:https://doi.org/10.1021/acs.est.7b05772· OSTI ID:1601828

Notini, Luiza ^[1]; Latta, Drew ^[2]; Neumann, Anke ^[1]; Pearce, Carolyn I. ^[3]; Sassi, Michel JPC ^[3]; N'Diaye, Alpha T. ^[4]; Rosso, Kevin M. ^[3]; Scherer, Michelle ^[1]

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1. University of Iowa
2. Argonne
3. BATTELLE (PACIFIC NW LAB)
4. Lawrence Berkeley National Laboratory

Despite accumulating experimental evidence for Fe(II)-Fe(III) oxide electron transfer, computational chemical calculations suggest that oxidation of sorbed Fe(II) is not energetically feasible unless defects are present. Here we used isotope specific 57Fe Mössbauer spectroscopy to investigate whether Fe(II)-goethite electron transfer is influenced by defects. Specifically, we heated the mineral to try to anneal the goethite surface and ground goethite to try to create defects. We found that heating goethite results in less oxidation of sorbed Fe(II) by goethite. When goethite was re-ground after heating, electron transfer was partially restored. X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) of heated and ground goethite confirm that heating and grinding alter the surface structure of the goethite. We propose that the heating process annealed the surface and decreased the number of sites where electron transfer could occur. Our experimental findings suggest that surface defects play an important role in Fe(II)-goethite electron transfer as suggested by computational calculations. Our finding that defects influence heterogeneous Fe(II)-goethite electron transfer has important implications for Fe(II) driven recrystallization of Fe oxides, as well as X and Y.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1601828
• Report Number(s): PNNL-SA-131667
• Journal Information: Environmental Science & Technology, Journal Name: Environmental Science & Technology Journal Issue: 5 Vol. 52
• Country of Publication: United States
• Language: English