Fourier Transform Infrared Spectroscopy of Clay Size Fraction of Cretaceous-Tertiary Kaolins in the Douala Sub-Basin, Cameroon

The structural order of Cretaceous-Tertiary kaolins of the Douala Sub-Basin in Cameroon was determined in this study. This was achieved using Fourier Transform Infrared spectroscopy (FTIR) with attenuated total reflectance (ATR) on the Bomkoul, Dibamba, Ediki, Logbaba, Missole and Yatchika kaolins. Transmittance spectra of 20 samples were recorded in the mid-infrared regions (MIR). Results show that most of the kaolins had the four distinguishable bands in the hydroxyl (OH) stretching region, though the second transmittance band (3670 cm(-1)) had low intensities. The hydroxyl stretching of water bands (3457 and 3442 cm(-1) for KGa-1b and KGa-2, respectively) were mainly observed in all Logbaba samples at 3443 cm(-1) and 3445 cm(-1). The two bands reflecting OH deformation of inner-surface hydroxyl and inner hydroxyl groups (937 and 915 cm(-1)) were quite visible in the Bomkoul, Dibamba, Logbaba and Missole II samples; slightly visible in all Yatchika and two of the Ediki; and not visible in Missole I and one of the Ediki samples. Therefore, based on the empirical classification of the degree of order of kaolinite, 10 of the studied samples had ordered structures. Three displayed partially ordered structures; four had poorly ordered structures, and three exhibited disordered structures. This study revealed that kaolins from Dibamba, Logbaba and Missole II in the Douala Sub-Basin had the best crystallinity, which is one of the important characteristics needed for industrial applications.