Mineral-Water Interface Dynamics: The Complex Interactions of Redox Active Metals With Manganese Oxide Surfaces

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Hochella9902996The underlying objective of this project is to advance the understanding of the interactions between various manganese oxide minerals and redox active, environmentally important aqueous metals, specifically cobalt and chromium. The specific goals in this study are: to characterize (for the first time) the atomic and electronic surface structure of certain manganese oxides (manganite, hollandite and pyrolusite) using scanning tunneling microscopy and spectroscopy; to describe redox interactions (including oxidation/reduction, sorption/desorption, and dissolution processes) between several manganese oxides (manganite, hollandite, pyrolusite, and birnessite) and aqueous Co(II) and Cr(III) using principally fluid-cell atomic force microscopy, Auger and X-ray photoelectron spectroscopies, and wet-chemical techniques, as well as scanning tunneling microscopy and spectroscopy; and to develop new models for these interactions which combine our observations and assessments with the excellent store of information already available for many of these aqueous metal - mineral interactions. The research performed in this project will allow us to address previously unresolved issues concerning environmentally important, redox-mediated mineral-water interface reactions. Such issues include surface heterogeneity, various temporal aspects, the role of near-surface absorption and diffusion, and specific structural, chemical, and physical factors that control aqueous metal oxidation efficiencies.