LAUSR

The thermal characteristic behaviors of two kaolinite samples selected from Qingshuihe region in Inner Mongolia in China were studied through thermogravimetry, derivative thermogravimetry, and differential scanning calorimetry (TG–DTG–DSC), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The activation energies of dehydroxylation for the two kaolinite samples (determined as Kaol-1 and Kaol-2) were calculated based on KAS and FWO methods. The XRD results indicated that Kaol-1 and Kaol-2 both were determined as kaolinite, and a small amount of quartz, but the Kaol-2 presented many amorphous organic matters. The TG–DSC results displayed the adsorbed water desorption and dehydroxylation with the temperature increased from 200 to 1100 °C. The dehydroxylation is followed as the intensities decrease in the bands at 3690 cm−1, 3620 cm−1 and 914.0 cm−1 attributing to the stretching mode of inner surface hydroxyls, and which disappeared when the temperature reached at 600 °C. The endothermic peak temperature of dehydroxylation for Kaol-2 presented higher than that of Kaol-1, which may be attributed to present of amorphous organic matter and was in agreement with the XRD data. The maximum endothermic temperature of dehydroxylation increased both for Kaol-1 and Kaol-2 with the increase in heating rate, which was attributed to more sufficient decomposition as the decrease in heating rate. The thermal kinetic analysis indicated that the dehydroxylation reaction of Kaol-1 should be a single kinetic mechanism, but the E of Kaol-2 decreased as α increasing from 0.2 to 0.5 and then gradually increased with the increase of α. The average E of dehydroxylation for Kaol-2 both was lower than that of Kaol-1 based on Kissenger–Akahira–Sunose and Flynn–Wall–Ozawa methods, which was attributed to the relatively higher organic carbon content in Kaol-2.