Iron oxides are ubiquitous. These tiny, often nanoscale, particles profoundly influence the quality of our water, air, and soil through the biologically-driven redox cycling between ferric and ferrous iron. We have used stable Fe isotopes in conjunction with 57Fe M�ssbauer spectroscopy to study redox reactions between ferrous Fe and Fe oxides, as well as Fe containing clays. Our results have shown that sorbed Fe(II) is oxidized by Fe(III) in Fe oxides, such as goethite, hematite, ferrihydrite, magnetite, and structural Fe(III) in clays and that Fe(II)-Fe(III) electron transfer initiates extensive atom exchange between Fe oxide and aqueous Fe(II). We present a new conceptual framework that incorporates experimental evidence for Fe(III)-Fe(II) electron transfer, bulk electron conduction, and Fe atom exchange to describe the reaction of Fe(II) at the Fe mineral- water interface and discuss the implications of the new conceptual model for important environmental processes, such as trace metal cycling and contaminant fate. Specifically, we will present evidence for release of Mn from Fe oxides during Fe(II) catalyzed goethite recrystallization and discuss how arsenate behaves during this Fe oxide recrystallization process.

Fe(II) sorption at the Fe mineral-water interface: A new conceptual framework and its implications for metal cycling

246th National Meeting (2013)

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