Hydrothermal Synthesis of Kaolinite

Abstract

Recent studies on the hydrothermal synthesis of kaolinite, particularly the results of the Special Research Program for Important Regional Technology, AIST, MITI, on the “Synthesis Technology of Artificial Clay for High Performance Ceramics”, are hereby introduced and reviewed. The formation of kaolinite depends on the structure of raw material, as well as the chemical composition of reaction system, pH of the system, temperature, reaction period, and some other factors that would greatly influence its formation. These factors are complicatedly related to each other, however they are very important conditions of the synthesis. Amorphous intermediate phases were found in at least two cases of the reaction processes of kaolinitization. The presence of the intermediate phases and the dependence of kaolinite formation on the structure of raw material suggest that molecular-clusters consisting of polycondensed SiO₄ tetrahedra are the minimum units in the reaction mechanism of kaolinitization.