Characterization of Chemical Species Adsorbed on Mineral Surface by X-ray Absorption Spectroscopy

Daisuke Kawamoto

    The adsorption behavior of dissolved species on mineral surfaces plays a crucial role in geochemical and environmental processes.  Recent studies have revealed that the adsorption of the dissolved species onto (hydr)oxide surfaces is often not the final stage of the solid-liquid interfacial reaction, and it can be followed by subsequent reactions such as redox reaction of the adsorbed species and dissolution of (hydr)oxides.  Furthermore, it has been reported that the dissociation of water molecules chemisorbed onto carbonate mineral surface results in the formation of surface functional groups, specifically > CaOH and > CaCO3H (“>” represents the mineral lattice).  Therefore, characterization of the adsorbed species is essential for elucidating the mechanisms of the adsorption and the associated chemical reactions.  This paper reviews two studies that investigated the chemical states and structure of species adsorbed onto mineral surfaces using X-ray absorption spectroscopy.  First, the mechanism by which Au(III) species adsorbed onto the δ-MnO2 surface is reduced to metallic gold is introduced.  Second, the adsorption mechanism of Cd species onto the CaCO3 (calcite) surface is discussed and interpreted based on the surface complexation model.

Advances in X-ray Chemical Analysis Japan

株式会社アグネ技術センター

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