Manganese valence and mineral surface structure determined with in situ soft x-ray spectroscopy
Glenn Waychunas, David Shuh, and Mario Villalobos
Contact: Glenn Waychunas, 510/495-2224, GAWaychunas@lbl.gov
Research Objectives
Manganese (Mn) minerals have high surface reactivity, redox potentials that can either reduce or oxidize adsorbed species, and high surface areas (fine grain sizes). These aspects make them extremely significant players in metal sequestration due to strong sorption and alteration in valence states (and hence solubility products) of solution species. Our goals are to determine how much information about Mn valence states and surface structure (i.e., surface mineral phase) can be extracted from K-edge oxygen and L-edge manganese x-ray fluorescence spectra, measured at the Advanced Light Source (ALS) at Berkeley Lab.
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 Mn L-edge flurescence spectra for Mn minerals with different structures and valences. The differences in the Mn (II) spectra result from the varied coordination environments of Mn in each mineral (rhodochrosite—6 coordination; spessartite—8 coordinated; rhodonite—5 and 6 coordinated). Both features and energy positions are characteristic of the Mn valence state.
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