FTIR spectroscopy of some Brazilian clays

Abstract

This work describes the FTIR spectroscopy of 05 bentonites and 03 kaolins from Brazil. All clay were previously dried at 60°C and sieved through the screens 200 and 325 mesh, before characterization by XRD and FTIR. Bentonite samples showed characteristic well-resolved peaks around 3620-3616 cm-1, attributed to the OH stretching of structural hydroxyl groups. Kaolin samples showed characteristic peaks near 3690 cm-1 and 3675 cm-1, assigned to the OH-stretching of the inner surface. A characteristic peak at 908 cm-1 has been previously linked to the presence of kaolinite, whose relative intensity in the spectra suggested differences in the kaolinite content in the clays. Peak around 780 cm-1 revealed the predominance of Fe3+MgOH over Fe3+AIOH and MgAlOH. Polycationic character of both bentonites and kaolins were clearly distinguished. Differences among the clay samples were linked to their chemical constitution, the amount of accessory minerals and the presence of structural substitutional cation(s).