Modification of kaolinite surfaces by mechanochemical treatment

Kaolinite surfaces were modified by grinding kaolinite/quartz mixtures with mole fractions of 0.25 kaolinite and 0.75 quartz for periods of time up to 4 h. X-ray diffraction shows the loss of intensity of the d(0 0 1) spacing with mechanical treatment resulting in the delamination of the kaolinite. Thermogravimetric analyses show the kaolinite surface is significantly modi fied and surface hydroxyls are replaced with water molecules. Changes in th e molecular structure of the surface hydroxyls of the kaolinite/quartz mixt ures were followed by infrared spectroscopy. Kaolinite hydroxyls were lost after 2 h of grinding as evidenced by the decrease in intensity of the OH s tretching vibrations at 3695 and 3619 cm(-1) and the deformation modes at 9 37 and 915 cm(-1). Changes in the surface structure of the OSiO units were reflected in the SiO stretching and OSiO bending vibrations. The decrease i n intensity of the 1056 and 1034 cm(-1) bands attributed to kaolinite SiO s tretching vibrations were concomitantly matched by the increase in intensit y of additional bands at 1113 and 520 cm(-1) ascribed to the new mechanical ly synthesized kaolinite surface. Mechanochemical treatment of the kaolinit e results in a new surface structure.