Reductive Transformation of Iron Oxides: Coupled Solution and Solid-State Pathways
EMSL Project ID
25629
Abstract
Reductive transformation of Fe(III)-oxides such as  Fe2O3 (hematite) by aqueous dissolution / re precipitation is a central part of the natural biogeochemical iron cycle in the environment. This transformation involves conversion of surface Fe(III) to Fe(II) by electron transfer from adsorbed reductant molecules followed by Fe(II) solubilization and precipitation of new phases. The process can enter an autocatalytic stage when released Fe(II) re-encounters and reduces the hematite surface. Some Fe(III)-oxides such as hematite have a propensity for fast charge redistribution and limited electron diffusion by solid-state electron transport. We propose a closely-coupled experimental and theoretical / computer modeling study that focuses on characterizing the pathways involved in the reductive transformation of hematite. The central objective is to determine mechanisms of transformation by linking surface-specific microscopic observations in conjunction with using a combination of small and large-scale molecular simulations. Computational molecular modeling in the form of molecular dynamics (MD) simulations, ab initio calculations, and kinetic Monte Carlo simulations (KMC) will be performed to develop one-of-a-kind atomistic models that will allow us to assess the effects of solid-state charge migration on the rate of growth and the morphology of dissolution and growth features for comparison with the experimental observations. We request access to the ambient scanning probe microscopy laboratory in the EMSL building in room 1544 under the purview of the Environmental Spectroscopy and Biogeochemistry Facility. We request occasional access to the XRD laboratory, the electron microscopy laboratory, and the XPS laboratory. For computational resources, we request 150,000 node hours on mpp2 and access to the SGI system 'nwvisus' and the Linux cluster 'Spokane'.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-05-31
End Date
2010-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
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