University of Wisconsin–Madison

Interfacial Biogeochemistry

Framework model of a mineral surface. Image: T.A. Oleson, N. Sahai.

Interfacial biogeochemistry deals with the fundamental physical and chemical processes controlling the thermodynamics and kinetics of interactions between inorganic and organic species in solution and at mineral surfaces, whether in the natural geological environment, in industrial processes, or within the human body.

Current research in Nita Sahai’s program includes studies of toxic arsenic remediation by coprecipitation of phosphate and oxyhydroxide phases; biomimetic nanosilica synthesis by the catalytic action of amine functional groups that mimic enzymes in diatoms and sponges; formation/disruption of cell-membrane phospholipid bilayers at oxide surfaces; development of structure-activity relationships to predict the hydroxyaptite-nucleating ability of oxide- and silicate-based bioceramics and bioglasses that are used as prosthetic, orthopedic and dental implants; and understanding the role of specific proteins in nucleating hydroxyapatite in human bones. A combination of experimental and modeling techniques are used, including aqueous analytical methods (e.g. ICP-AES, UV-VIS, AA), calorimetry, Infra-Red, Raman and NMR spectroscopy, Atomic Force Microscopy, Electron Microprobe and High-Resolution Transmission Electron Microscopy, quantum chemical molecular orbital calculations, molecular mechanics and molecular dynamics simulations. Professor Sahai’s program includes active collaborations with faculty in the Departments of Geochemistry, Chemistry, Soil Science, Biochemistry, and the Environmental Chemistry and Technology Program (ECT) at University of Wisconsin. Professor Sahai has appointments in Geology and Geophysics, and affiliate appointments in Chemistry and ECT.

Current research in Eric Roden’s program includes studies of precipitation and dissolution reactions coupled to enzymatic electron transfer at the surface of Fe(III) oxides; reductive precipitation of nanoparticulate uranium and other trace/contaminant metals in aqueous solution and on the surface of oxide and silicate minerals; and enzymatic oxidation and phase conversion of ferrous iron-bearing minerals. Studies are conducted in both mineralogically defined systems as well as physically and chemically heterogeneous natural soil and sediment materials.

Current research in Huifang Xu’s program includes studies of the relationship among morphology, size, reactivity and stability of nanocrystals; chemical reactions (with focus on sorption, desorption, precipitation, dissolution, and replacement reactions) in nanoporous environments; self-assembled nanostructures in the earth systems; and surface tension and surface energy of minerals and materials.