A VIBRATIONAL SPECTROSCOPIC STUDY OF THE ADSORPTION OF 4,4'-BIPYRIDYLBY SEPIOLITE AND SMECTITE GROUP CLAY-MINERALS FROM ANATOLIA (TURKEY)

The adsorption of 4, 4'-bipyridyl by natural sepiolite and smectite gr oup clay minerals (bentonite, hectorite and saponite) from Anatolia (T urkey) has been studied using vibrational spectroscopy. Investigation of Fourier-transform infrared and Fourier-transform Raman spectra of a dsorbed 4,4'-bipyridyl indicate the presence of chemisorbed species. H owever, any evidence for the generation of anionic species on the surf ace of the phyllosilicates has not been detected. It is proposed that the adsorbed bipyridyl molecules on sepiolite are centrosymmetric and H-bonded to the surface hydroxyls through both the nitrogen lone pairs as bidentate ligands. The adsorbed bipyridyl molecules on the smectit e group clays are coordinated to exchangeable cations both directly an d also indirectly through water as monodentate ligands. XRD patterns o f the clays studied are also recorded.