Detection of four different OH-groups in ground kaolinite with controlled-rate thermal analysis

The thermal behaviour of mechanochemically treated kaolinite has been investigated under dynamic and controlled rate thermal analysis (CRTA) conditions. Ten hours of grinding of kaolinite results in the loss of the d(001) spacing and the replacement of some 60% of the kaolinite hydroxyls with water. Kaolinite normally dehydroxylates in a single mass loss stage between 400 and 600degreesC. CRTA technology enables the dehydroxylation of the ground mineral to be observed in four overlapping stages at 385, 404, 420 and 433degreesC under quasi-isobaric condition in a self-generated atmosphere. It is proposed that mechanochemical treatment of the kaolinite causes the localization of the protons when the long range ordering is lost.