Dehydroxylation and CO2 incorporation in annealed mica (sericite): An infrared spectroscopic study
2005
Dehydroxylation and incorporation of CO2 in mica (sericite-2M1) during high-temperature annealing
has been investigated in detail using infrared (IR) spectroscopy. The dehydroxylation is characterized
by a dramatic change of the OH– ion spectrum and the appearance or development of different extra
species (CO2, CO3
2–, and OH–). A signifi cant decrease in the K-O bond strength and a complex distortion
of the silicon-oxygen tetrahedra were also observed. The general similarities between the spectra of
the untreated and dehydroxylated sericite show that the layered framework is somewhat preserved in
sericite dehydroxylate. The results suggest that the incorporation of CO2 into the structures of the heated
materials is associated with or enhanced by the dehydroxylation process, although the two processes
have different reaction mechanisms. The CO2 contents in heat-treated sericite show a correlation with
the loss rate of hydroxyl. A weak O-H stretching absorption band near 3480 cm–1 developed during
dehydroxylation and it disappeared above 1100 °C. The results suggest that the developed additional
O-H stretching signals and the thermally induced CO2 do not structurally stabilize each other, as upon
further heating the two different types of components vanished at different temperatures.
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