Synthesis of zeolites 4A and HS from natural materials

Synthesis of zeolites 4A and HS from natural materials. The crystallization of the zeolite HS was studied during the synthesis of the zeolite 4A using several raw materials like diatomite, kaolin and bentonite. First, these three materials were activated mainly by melting in the presence of caustic soda. The comparison with the pure reagents (solution of sodium silicate and sodium aluminate) as a reference allowed to deduce that an appearance of the zeolite HS during the synthesis is observed with most of the raw materials. Its formation takes place when the concentration of aluminium decreases below the value corresponding to the pure products in the liquid phase. This situation takes place when the reactant gel is heterogeneous, which is characteristic of all the raw materials studied. This seems to be the reason for the formation of zeolite HS.