FT-IR spectroscopic investigation of adsorption of 3-aminopyridine on sepiolite and montmorillonite from Anatolia

The adsorption of 3-aminopyridine by natural sepiolite and montmorillonite from Eskisehir (Anatolia) was investigated in the temperature range from 20 to 125 degreesC by infrared spectrometry using a variable temperature unit . The spectroscopic results indicate that the 3-aminopyridine molecules ads orbed on sepiolite are coordinated to Lewis acidic sites and/or surface hyd roxyls by H-bonding interaction through pyridine ring nitrogen lone pairs. Surface Bronsted acid strength of sepiolite is weak and 3-aminopyridinium i s not detected under the conditions applied in this study. It must be noted that the adsorption of aminopyridine affected the hydroxyl group vibration s of sepiolite. The intercalation of 3-aminopyridine within montmorillonite has been shown by X-ray diffraction to increase the interlayer spacing. IR spectroscopy indicates that sorbed 3-aminopyridine molecules by montmorill onite are mostly coordinated to exchangeable cations directly or indirectly through water bridges. The formation of 3-aminopyridinium cation is also d etected at elevated temperatures. (C) 2001 Elsevier Science B.V. All rights reserved.