| Abstract
| - The progressive adsorption of N-methylformamide (NMF) onto Ca-, Mg-, and Na-exchanged Wyomingbentonite (Mn+−SWy-2) together with its subsequent thermal desorption has been studied using a varietyof complementary techniques. The derivative thermograms (DTG) for the desorption of NMF from Mn+−SWy-2 exhibit three maxima at temperatures which depend on the exchange cation. In Mg−SWy-2 thesemaxima occur at 130, 200, and 400 °C, whereas in Na−SWy-2 they occur at 100, 150, and 190 °C. Eachof these maxima has been assigned to different sites and/or environments for sorbed NMF using variabletemperature-X-ray diffraction (VT-XRD) and variable temperature-diffuse reflectance infrared Fouriertransform spectroscopy (VT-DRIFTS). Each fully loaded Mn+−SWy-2/NMF complex has two layers of NMFin the gallery, which decreases to a single layer prior to the complete removal of NMF from the complex.The temperatures at which major weight losses occur coincide with decreases in the interlayer spacing.VT-DRIFTS has shown that at low temperatures NMF was removed from NMF clusters, similar to thosein liquid NMF, while at high temperatures the NMF molecules are firmly bound and directly coordinatedto the exchangeable cations. Unusual shifts in the C−H and N−H absorption bands were observed, indicatinga unique orientation of these groups, which probably reflects their keying into the hexagonal cavities ofthe tetrahedral sheet of the aluminosilicate layer.
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