Characterization of structure and properties of bioorganoclays - perspective hybrid materials

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Controlled preparation of bioorganoclay composites from microbial matter and clay minerals is of great environmental, geological, and technological interest because materials with specific properties can be obtained. Further, interactions between microbial matter and clays are a common interfacial phenomenon in the biogeochemical environment, such as in soils and sediments. However, fundamental mechanisms governing formation and interactions of these materials are still poorly understood. The objective of the proposed project is to prepare, characterize, and model new bioorganoclays based on organic matter of microbial origin and selected clay minerals. Expected are materials with new specific properties, for example enhanced sorption capacity. The proposal is based on the hypothesis that depending on origin, type, and size of bioorganic molecules or microbial material and on the type of the clay, bioorganoclays with different structure and properties can be prepared. Two basic types are expected, i) bioorganoclays having clay particles coated by bioorganic matter with only limited or no penetration into interlayer galleries (kaolinite-based), and ii) bioorganoclays having distributed bioorganic matter in the interlayer galleries and/or on the external surfaces of clay particles (montmorillonite-based). With respect to this also differences in shape and size of biorganoclay particles, pore volume structure, stability and binding of the bioorganic coating to clay matrices, and the amount and type of active sites on surfaces are expected. Interaction mechanisms between bioorganic material and clays, and the resulting structure and physicochemical properties will be explored by multiple experimental methods (e.g. XPS, NMR, TEM, NanoSIMS) in combination with molecular modeling. We plan to use pure bioorganic molecules (e.g. phospholipids) and also more complex microbial biomass. Characterization of the bioorganoclays prepared from pure biomolecules will help in the understanding of interactions of more complex biomass with clays. This approach will lead to complex and detailed (molecular-scale) characterization of the bioorganoclay materials, e.g. arrangement of the bioorganic species in interlayer and on external surfaces of clays. Referring to the physicochemical properties, changes of the adsorption capacity of the bioorganoclays with respect to type and amount of the bioorganic materials and clay minerals will be in focus. To verify this, experiments and computer simulations will be focused to determine the structure, composition, and properties of the prepared bioorganoclays. The proposed bilateral project will profit from effective collaboration between the German (experiments) and Austrian (modeling) group.