A new method to determine the ratio of clay minerals in mixtures by IR spectroscopy.

A method by IR spectroscopy was used to ascertain kaolinite and smectite in mixtures. Samples were prepared by mechanical mixture of two kaolinites with different crystallinity (KGa-1, KGa-2) and a montmorillonite (SAz-1). Kaolinite can be detected in amounts of less than 1%. The NH4+-saturated montmorillonite was easily determined using the NH4+ ion. The relative absorbances of nu (OH) for kaolinites and smectite were measured. The relative absorbance of nu (OH) for both kaolinite samples was the same indicating that the structural defects of kaolinite do not influence their nu (OH) absorbance. The ratio of the relative absorbance of nu (OH) for kaolinite and smectite was 4.9. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.