FTIR Spectral Components of Schwertmannite

摘要

Fourier transform infrared (FTIR) spectral components of three dominant groups of sulfate species in synthetic schwertmannite (Fe_8O_8(OH)_(6-X)(SO_4)_x·nH_2O) are presented. These components were extracted by multivariate curve resolution analysis of spectra obtained from N_2(g)-dry samples initially reacted in aqueous solutions (pH 3-9) at room temperature. Each component contains complex sets of bands that correspond to mixtures of similar species. We tentatively assign these components to sulfate ions that are hydrogen- (components Ⅰ and Ⅲ) and iron-bonded (component Ⅰ) to schwertmannite. Another component (Ⅱ) is assigned to protonated sulfate species. Heating experiments to 130 ℃ moreover confirmed this possibility for component Ⅱ. The spectral components extracted from this study can be used to identify dominant sulfate species in FTIR spectra of naturally occurring schwertmannite samples.