Synthesis of zeolites from mechanically activated kaolin clays

The hydrothermal treatment in NaOH solution of clays activated by grinding leads to the formation of different zeolites, whose nature depends on the amorphization of the clay obtained by applying a periodic stress by means of an oscillating mill. In this way, hydroxysodalite, mixtures of hydroxysodalite and NaA zeolite, or NaA pure zeolite can be obtained. In the present paper, it is shown that the product varies in composition, and is enriched in NaA zeolite as the crystalline structure of the clay is destroyed by grinding. It is proved that the activation by impact grinding is an alternative method to the classical calcination for the synthesis of the NaA zeolite.