Effect of particle size of calcite on the stacking order of kaolinite during mechanical grinding

Abstract

The effect of calcium carbonate (CaCO₃) particles on the stacking order of kaolinite, a layered clay mineral, during the mechanical grinding process was demonstrated by grinding of expanded kaolinite without impurities (Ex-Kaol), a methoxy-modified kaolinite, in the presence and absence of calcite with different particle sizes. The X-ray diffraction patterns of the ground raw materials revealed that the relative intensity of the reflection corresponding to stacking direction of kaolinite decreased in the absence of calcite particles. The presence of calcite particles suppressed the disruption of the stacking order of kaolinite due to the breaking of calcite particles. In addition, this suppression was weakened using calcite particles of smaller size. Meanwhile, the raw ground material containing smaller calcite particles converted into the targeted product faster than the raw ground material containing larger calcite particles. These results indicated that the particle sizes of raw materials are important for solid-state reactions including kaolinite.