Eggleston, C. M., University of Wyoming, Laramie, USA, carrick@uwyo.edu
Shankle, A. J., University of Wyoming, Laramie, USA, ashankle@uwyo.edu
Borman, C. J., University of Wyoming, Laramie, USA, cjborman@uwyo.edu
Moyer, A. J., University of Wyoming, Laramie, USA, amoyer@uwyo.edu

FROM LABORATORY TO FIELD: IRON OXIDE PROPERTIES, PHOTOCATALYTIC WATER OXIDATION, AND FE(III) PHOTOREDUCTION

Iron redox-cycling is key to many chemical processes relevant to environmental chemistry as well as to deep-time events like the origin of life and the deposition of banded iron formations. Hematite has been the subject of much recent study with regard to solar energy conversion. Photocurrents generated by water oxidation on hematite are 5 to 10 times greater when illuminating crystal edges (perpendicular to the [001] direction) than when illuminating parallel to the [001] direction. Hematites grown in the presence of water generate less photocurrent by water oxidation than "dry grown" hematites, probably because of an impurity-induced "intragap" state that mediates recombination. Finally, our work in a watershed in Wyoming (relatively high pH) shows elevated Fe(III) concentrations during periods of high light intensity. Isolation experiments reveal a substantial non-photochemical Fe reduction rate that is able to maintain steady-state Fe(II) concentrations against rapid oxidation in the dark. Exposure to sunlight results in more rapid Fe(II) release to solution (most likely from organic complexes) and very rapid oxidation by aqueous oxygen, resulting in elevated afternoon Fe(III) concentrations.

Oral presentation

Presentation is given by student: No
Session #:SS01
Date: Friday, June 13, 2008
Time: 10:45 AM

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