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Coupled Surface and Solid-State Charge and Ion Transport Dynamics at Mineral/Water Interfaces: Redox Transformation of the Iron Oxides

EMSL Project ID


This EMSL user proposal requests a continuation of EMSL access for a BES Geosciences supported project led by Dr. Rosso at PNNL. The past three years of research under this BES project we have been studying the interaction of Fe(II) with semiconducting Fe(III)-oxide minerals. This research has provided new insight into relationships between interfacial electron transfer processes, surface charge accumulation reactions, surface structure, and semiconducting properties of Fe(III)-oxides. Our EMSL-enabled experiments demonstrate a prospectively comprehensive model to explain the interplay among Fe(II) adsorption, interfacial electron transfer, bulk charge transport, and Fe(II) release (Yanina and Rosso, 2008). We have also invested significant effort into theory and simulation development, including seminal first principles calculations of electron transport at specific surfaces of Fe(III)-oxide crystals, and large-scale atomistic dynamics simulations of surface morphological evolution during dissolution. We propose to build on our findings using Fe(II) interaction with iron oxides as a model system for surface reactivity coupled to bulk transport processes. We will focus on determining the conditions and extent to which this coupling controls reductive dissolution and recrystallization of hematite, and the topotactic maghemite-magnetite transformation in the presence of aqueous Fe(II). The behavior of individual low-index crystal faces will be studied to closely link observations to fundamental aspects of site and surface structure. A combination of experiments and computational molecular simulations are proposed to develop a fundamental understanding of solution-dependent surface potential for directing crystallographic locations and the extent of Fe(II) adsorption, the kinetics of Fe(II)aq-Fe(III)oxide interfacial electron transfer, and the migration direction of injected electrons. Magnetite-maghemite transformation is a special case in which the diffusion of charge equivalents into or out of the solid may involve cation diffusion. We will attempt to develop large-scale dynamics simulations with an explicit representation of surface structure, bulk charge migration dynamics, and quantitative description of the surface potential for structurally specific oxide/solution interfaces. The proposed research is within the scope of the Geochemistry/Biogeochemistry and Subsurface Science EMSL theme, being closely aligned with sub-topical areas 'Linking molecular-scale processes to reactive transport' and 'Chemical and biological interactions at complex interfaces'.

Project Details

Project type
Large-Scale EMSL Research
Start Date
End Date


Principal Investigator

Kevin Rosso
Pacific Northwest National Laboratory

Team Members

Michel Sassi
Pacific Northwest National Laboratory

Sandra Taylor
Pacific Northwest National Laboratory

Vitali Alexandrov
University of Nebraska - Lincoln

Shawn M Chatman
Pacific Northwest National Laboratory

Carolyn Pearce
Pacific Northwest National Laboratory

John Loring
Pacific Northwest National Laboratory

Related Publications

Chatman SME, PP Zarzycki, T Preocanin, and KM Rosso. 2013. "Effect of Surface Site Interactions on Potentiometric Titration of Hematite (?-Fe2O3) Crystal Faces." Journal of Colloid and Interface Science 391:125-134. doi:10.1016/j.jcis.2012.09.081
Katz J.E., Zhang X., Attenkofer K., Chapman K.W., Frandsen C., Zarzycki P., Rosso K.M., Falcone R.W., Waychunas G.A., and Gilbert B. (2012) Electron small polarons and their mobility in iron (oxyhydr)oxide nanoparticles. Science 337, (6099) 1200-1203.
Singer DM, SME Chatman, ES Ilton, KM Rosso, JF Banfield, and G Waychunas. 2012. "U(VI) sorption and reduction kinetics on the magnetite (111) surface." Environmental Science & Technology 46(7):3821-3830. doi:10.1021/es203878c
Zarzycki P., Kerisit S., and Rosso K.M. (2011) Computational methods for intramolecular electron transfer in a ferrous-ferric iron complex. Journal of Colloid and Interface Science,361, 293-306.