Mechanistic Understanding of Metal Sorption by Phyllomanganates through Density Functional Theory

초록

The sorption processes of phyllomanganates (layer type Mn oxides) greatly impact the geochemical cycles of metals in environments ranging from the ocean floor to the land surface. In situ spectroscopy has provided valuable insights into the underlying sorption mechanisms on these minerals by identifying molecular-level surface species of trace metals. Accurate determination of metal surface speciation is challenging, however, because of ambiguities often encountered in attempting to interpret the spectra. Adding complexity to these issues, certain experimentally observed trends in metal sorption cannot be explained simply by invoking conventional chemical effects, such as differences in ionic radii or crystal field energies. Geometry optimizations performed using density functional theory, a first-principles approach based in quantum mechanics, can help to resolve these problems by providing highly detailed information about the structure, energetics, and electronic properties of both minerals and metal surface complexes, thus serving as a complementary approach to surface spectroscopy in elucidating sorption mechanisms. This chapter reviews recent applications of density functional theory which illustrate how it accomplishes this goal.

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