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.
ASJC Scopus subject areas
- Materials Science(all)