Separation of Adsorbed Formamide and Intercalated Formamide Using Controlled Rate Thermal Analysis Methodology

Controlled rate thermal analysis (CRTA) has been used to separate adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites. This separation is achieved by removal of the sample at the end of the controlled isothermal desorption step. The temperature of this isothermal desorption is dependent on the use of open or closed crucibles in the thermal analysis unit but is independent of the formamide/water ratio. X-ray diffraction shows that the formamide-intercalated kaolinite remains expanded after formamide desorption with a d (001) spacing of 10.09 Å. Further heating to 300 °C results in the deintercalation of the formamide-intercalated kaolinite. DRIFT spectroscopy shows differences between the infrared spectra of the adsorbed and formamide-intercalated kaolinites. An intense band observed at 3629 cm - 1 is attributed to the inner surface hydroxyls hydrogen bonded to the formamide. The adsorbed formamide-intercalated kaolinites contain adsorbed water and show intensity in the 1705 cm - 1 band, which is absent in the CRTA-treated formamide-intercalated kaolinites.