Effect of original crystal size of kaolinite on the formation of intercalation compounds of coal-measure kaolinite

Abstract

Coarse crystalline (14.8–19.8 µm) and crypto crystalline (0.51–0.92 µm) coal-measure kaolinite were selected to explore the effect of original crystal sizes on intercalation. Characterization methods of SEM, XRF, XRD, FT-IR, and TG-DTG were utilized to study the original crystal size distribution, chemical composition, crystal structure changes, vibrational characteristics of functional groups, and thermal stability before and after intercalation. The test results reflected that the original crystal size significantly affects the formation of intercalated compounds. Coal-measure kaolinite intercalation compounds have been successfully prepared. Nonlinear fitting curves between the different characterization methods and the original average crystal size showed a significant positive correlation. The results showed that the intercalation effect of coarse crystalline was more significant than those of crypto crystalline, that is to say, the larger the original crystal sizes of coal-measure kaolinite, the higher the intercalation rate, the higher the grafting rate and the more pronounced the mass loss rate. Based on the theory of surface energy and surface charge of mineral particles, the electrical double layer theory which was different from the previous researchers was proposed to explain the intrinsic mechanism of the effect of original crystal size on intercalation.