NIRT: Experimental and Theoretical Investigations of Aqueous Geochemical Interfaces - The Role of Nanoscale and Molecular Structures in Dictating Environmental Reactivity

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0404400TrainorThe focus of this proposal is an interdisciplinary approach to molecular and nanoscale investigations of iron-oxide surface structure and reactivity. Intellectual merit of the proposed activity: The research proposed here will utilize state-of-the-art experimental and theoretical methods to provide unique information about the fundamental controls on reactivity of iron-oxides. Experiments using both single crystal substrates and nanoparticle composites of hematite will be used to determine reactivity trends with respect to adsorption of contaminant metal ions, and how these vary with surface orientation, surface quality, and reaction with "surface modifying species". The complementary nature of the proposed techniques will allow multiple avenues of investigation to be pursued in a coherent and synergistic effort and will result in a better understanding of the systems under investigation as compared with decoupled, independent studies. The proposed methodology also overcomes current limitations on in-situ surface structural studies of nanoscale particles by taking full advantage of recent advances in synchrotron-based surface structural techniques and periodic ab-initio methods. One of the main contributions of this work will be to explain reactivity trends in terms of molecular scale surface structure and nanoscale surface topography/defect density. This will allow the important question of scaling to be addressed since the effects of surface defects on reactivity are anticipated to increase dramatically as particle size decreases to the nanometer scale. This research team is particularly well qualified for an interdisciplinary collaboration aimed at obtaining fundamental information on mineral surface structure and reactivity relevant to the environmental interface chemistry.Broader impacts of the proposed activity: Chemical processes at nanoscale solid/aqueous solution interfaces have far-reaching impacts in environmental chemistry and geochemistry, as well as in various areas of technology that depend on surface reactions, such as heterogeneous catalysis and corrosion control. The work proposed here will lead to improved predictions about metal ion sequestration on (and release from) mineral surfaces, which will ultimately lead to improvements in quantitative models used for assessment of contaminant risk and the design of contaminant remediation strategies. While pursing the technical goals of this project, a major emphasis will be placed on providing educational opportunities to undergraduate, graduate, and post-doctoral students. Student participants will be involved in all aspects of this project, thereby providing research experience in synchrotron-based experimentation, ab-initio electronic structure calculations, and analytical laboratory practices. Thus one of the main impacts of this project will be to produce the next generation of scientists, including women and minorities, who are well trained in the theory and techniques of molecular environmental science, which is highly interdisciplinary and presents major challenges in terms of understanding fundamental chemical processes due to the complexity of environmental systems. Additional educational impact of this work will be reflected in the development of facilities and expertise at the member institutions and by dissemination of results to the broader scientific and general community through peer reviewed publications and presentations.