Infrared Studies of Surface Acidity and Reversible Folding in Palygorskite

摘要: The infrared absorption spectra of a palygorskite sample from Caceres, Spain, showed two previously unreported bands in the OH-stretching region at 3420–3440 and 3220–3230 cm−1 after evacuation 90°–230°C. These bands, which reached maximum intensity was heated 150°C, were assigned to OH $$\begin{array}{*{20}{c}} H \\: \\ {Si - O Si\,and\,} \end{array}\begin{array}{*{20}{c}} A1} \end{array}$$ groups, respectively. To characterize nature these groups, pyridine adsorbed on sample. resultant suggest that 150°C folded groups protonated, resulting formation deformed pyridinium ion between 150° 290°C. A high concentration thermally stable Lewis-acid sites surface also noted.