Formation of Kaolinite in Inorganic and Organic Low-Temperature Systems

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9909561PI: Kathryn L. Nagy, University of ColoradoProject: Formation of Kaolinite in Inorganic and Organic Low-Temperature SystemsKaolinite is a clay mineral that forms in tropical or temperate weathering environments or during the burial diagenesis of sandstones and shales. Kaolinite is mined for its properties such as color and light reflectivity, which are important characteristics of industrial products such as ceramics and paper coatings. It is a key mineral used to isotopically trace fluid flow pathways and past climate change, that alters porosity and permeability in subsurface sandstones, and that dominates certain soils. Although natural kaolinite has been extensively investigated using surface and microscopic analytical techniques, quantitative knowledge of fundamental controls on and rates of kaolinite formation at low temperatures is lacking. In this project, the roles of dissolved organic molecules, natural organic materials, mineral substrates, solution composition, and temperature in controlling the formation of kaolinite will be investigated. The approach combines well-controlled kinetics experiments, full characterization of solutions and solids, and empirical molecular modeling of interactions between dissolved ions and organic molecules with the mineral surfaces. Organic molecules will represent soluble humic substances and organic exudates from plants and bacteria. Results will provide a rate law for kaolinite nucleation and growth that can be used to model natural processes in soils, sediments, and sedimentary rocks and may also be applied in the related fields of soils science, petroleum exploration, and industrial mineralogy.