Variable temperature diffuse reflectance infrared Fourier transform spectroscopic investigation of the effect of ball milling on the water sorbed to kaolin

Variable temperature DRIFTS has been used to investigate temperature variation of the number and population of the different environments occupied by water on unmilled kaolin and samples ball milled for 3, 10 and 30 min. Increasing the milling time resulted in structural damage of the kaolin and an increase in the amount of hydrogen bonded water indicated by bands in the OH stretching and bending regions. Curve fitting of the spectra, collected at 50 °C intervals in the temperature range 25–500 °C, established that the intensity of the bands diminished as the temperature was increased but also revealed bands that were more stable to high temperatures or were generated as the sample temperature was increased. Bands at 3750, 3386 and 3200 cm−1 and 1680, 1650, 1634 and 1600–1580 cm−1 were identified in the OH-stretching and bending regions, respectively. In particular a band at 1670 cm−1 has been attributed to strongly hydrogen bonded water which acts to hold the deformed kaolin sheets together. Upon aging the samples the intensity of this band decreased and was replaced by a band at 1630 cm−1. Boehmite was tentatively identified as a product of the milled kaolin.