Determination of the Ti speciation in commercial kaolins by Raman spectroscopy

Raman spectra of a selection of kaolins with widely varying TiO2 contents r evealed the presence of anatase in 17 of Is samples. A significant positive correlation was observed between the intensity of the main anatase Raman b and at similar to 145 cm(-1) and the total TiO2 Contents of the kaolins as determined by chemical analysis. No TiO2 modification other than anatase wa s detected in any of the samples. The determination of the anatase contents in kaolins by XRD becomes increas ingly difficult as the concentration of this mineral decreases below simila r to 0.5%. In contrast, anatase and brookite concentrations an order of mag nitude lower can still be readily identified by Raman spectroscopy. The spe cificity and sensitivity of Raman spectroscopy for these TiO2 polymorphs, c oupled with the simplicity and rapidity of measurement, therefore make this a viable technique for the routine study of these accessory minerals in ka olins.