Sorption reactions of aqueous metal cations and oxoanions with mineral surfaces is recognized as an important means of sequestering environmental contaminants and pollutants and lessening their environmental impact. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy has become one of the techniques of choice for determining the composition, geometric structure, and mode of attachment of cations and oxoanions to mineral surfaces. This field has evolved rapidly over the past 30 years since the first EXAFS studies of oxoanion sorption to Fe(III)-oxyhydroxides. Dr. Glenn Waychunas has been one of the pioneers in this field and is particularly well known for his classic study of arsenate adsorption to ferrihydrite (Fh), a common, naturally occurring nano-Fe(III)-hydroxide. This paper will review the development of the field of interface geochemistry, starting with the classic studies of Stumm and Schindler who used macroscopic adsorption isotherms to deduce molecular-level information about sorption complexes at mineral-water interfaces. The application of EXAFS spectroscopy, in particular, gave us the first definitive molecular-level information on sorption complexes. A number of examples of the systems to which a combination of adsorption isotherm measurements, EXAFS spectroscopy studies, and computational chemistry have been applied will be reviewed. In addition, some of the factors affecting the binding of aqueous cations and oxoanions at mineral surfaces will be reviewed, including pH, surface charge, ionic strength, particle size, nano-confinement, and the presence of natural organic matter and microbial biofilm coatings on mineral surfaces.      <br/>

X-ray absorption spectroscopy studies of sorption reactions at mineral-aqueous solution interfaces

253rd National Meeting (2017)

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