Redox reactions at mineral-water interfaces in nature are affected by adsorbed and dissolved cations, anions, and biomolecules, as well as by structural impurities in the underlying mineral. We discuss the impact that adsorbed anions and structural Al3+ have on Fe2+-Fe3+ electron transfer and atom exchange reactions that occur between aqueous Fe2+ and the Fe3+ oxy-hydroxide goethite. Using 57Fe M�ssbauer spectroscopy and stable isotope tracers, we find that anions (CO32-, PO43-, and SiO44-) exert little impact on Fe2+- Fe3+ electron transfer at the mineral-water interface; in contrast, structural substitution of Al3+ in goethite significantly impacted the measured Fe2+-Fe3+ atom exchange. Additionally, we have interrogated the influence that Ti impurities in magnetite have on the reduction of the contaminant radionuclide U6+. Using x-ray absorption spectroscopy we find that Ti doping has no discernible effect on the extent of U6+ reduction to U4+ by magnetite, but exerts an influence on the U4+ product produced.

Impurities at the mineral-water interface: Effects on Fe and U redox cycles

245th National Meeting (2013)

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