Raman spectroscopy of potassium acetate‐intercalated kaolinites over the temperature range 25–300,°C

Raman spectra of the hydroxyl‐stretching region of potassium acetate‐intercalated kaolinite were obtained under an atmosphere of both air and nitrogen using a thermal stage over the temperature range 25–300 °C. At 25 °C, an additional band at 3606 cm −1 attributed to the inner surface hydroxyl hydrogen bonded to the acetate ion is observed with a concomitant loss of intensity in the bands attributed to the inner surface hydroxyls. Heating the intercalated complex to 50 °C results in two hydroxyl‐stretching wavenumbers at 3594 and 3604 cm −1 . At 100 °C, the bands shift to 3600 and 3613 cm −1 . At temperatures from 100 to 300 °C, bands are observed in similar positions. Upon cooling in air to 25 °C, the acetate‐bonded inner surface hydroxyl stretching wavenumber shifts back to 3606 cm −1 . Upon heating the intercalated kaolinite to 300 °C under an atmosphere of nitrogen and upon cooling the acetate‐bonded inner surface hydroxyl stretching wavenumber is observed at 3601 cm −1 . Upon cooling to 150 °C and subsequently to 25 °C, two bands are observed at 3611 and 3600 cm −1 . Upon rehydration, the hydroxyl stretching wavenumber returns to 3606 cm −1 . The changes in the Raman spectra of the hydroxyl‐stretching region during dehydration and rehydration are reversible. When the potassium acetate‐intercalated kaolinite is heated to 300 °C and cooled to 25 °C, the inner‐hydroxyl band is observed at 3630 cm −1 . The shift in the wavenumber of the inner hydroxyl band is attributed to the insertion of the potassium ion in the ditrigonal cavity of the siloxane layer. Copyright © 2001 John Wiley & Sons, Ltd.