Synthesis of clay minerals

Synthetic clay minerals provide new choices of layered solids and can be tailored to promote specific properties. They give better understanding of various processes involved in the formation of natural mineral counterparts. This review summarizes recent advancement on synthetic clay minerals such as kaolinite, pyrophyllite, mica, smectite, chlorite, and sepiolite. The syntheses were generally performed either at low temperature or at a higher temperature by hydrothermal technology. The crystallization, properties and morphology of synthetic clay minerals were influenced by the chemical composition and structure of starting materials as well as hydrothermal conditions. Isomorphous substitution and the influence of such substitution on the structure and morphology of the clay minerals were extensively studied. Hydrothermal syntheses of pyrophyllite polymorphs were affected by several factors including anions present in the solution, the state and quantity of the interlayer cation, and counter anion in solution. The effects of fluorine in hydrothermal synthesis were discussed. Organo-montmorillonite and organo-hectorite were obtained by direct incorporation of polymers or organic species during synthesis. The synthesis chemistry provided a better understanding of the formation mechanism, variation in physico-chemical properties and subsequently new applications for clay minerals.