Covalent grafting of pyridine-2-methanol into kaolinite layers

Abstract

A novel hybrid organic-clay material was prepared by grafting of pyridine-2-methanol in the interlayerspace of kaolinite by using a kaolinite/methanol compound as an intermediate. A kaolinite/methanolcompound was obtained by guest displacement process of a kaolinite/N-methylformamide pre-interca-lation complex with methanol. The structural, morphological and thermal properties of the hybrid mate-rial and intermediate species were examined by using X-ray powder diffraction, Fourier transforminfrared, thermal analysis, scanning electron microscopy and surface area measurement techniques.The X-ray powder diffraction patterns showed that the penetration of pyridine-2-methanol betweenthe kaolinite/methanol layers caused the emergence of a new peak at 6.51(2h) with the distance of13.57 Å. The pyridine-2-methanol species present in the kaolinite interlayers led to appreciable decreasesin the intensities of the peaks at 3696, 3667, 3650 and 938 cm 1which originate from inner-surfacehydroxyl groups of pure kaolinite and the new vibrational peaks belonging to the guest molecule wereappeared. The thermal analysis data confirmed that the removal of intercalated species occurred in thetemperature range 100–180°C, whereas the grafted pyridine-2-methanol molecules remained stableup to 350°C which may be explained by grafting of the pyridine-2-methanol molecules onto theinner-surface hydroxyls on the interlayer surfaces of kaolinite through Al–O–C covalent bond formations.The organic molecules located in the interlayer spaces caused significant alterations in the morphology ofthe pure kaolinite. The specific surface areas of the kaolinite–methanol and kaolinite-N-methylforma-mide compounds increased whereas that of kaolinite/pyridine-2-methanol hybrid material decreasedwith respect to that of pure kaolinite.