Abstract: The Effect of the water content on the growth of NaA zeolite membranes and the thickness control of the membrane were studied by secondary synthesis from clear solutions. The samples were characterized by SEM, TEM and XRD. It has been shown that different synthesis solutions resulted in the different growth process of NaA zeolite membranes. In the dilute synthesis solution [n(H₂O)/n(SiO₂)=(2 000)], the thinner NaA membrane with single-layer structure was formed by zeolite crystals growing only within the seed layer. On the contrary, in the concentrated synthesis solution ([n(H₂O)/n(SiO₂)=750],) the thicker NaA membrane with two-layer structure was formed by zeolite crystals growing outward from the topmost layer of the seeds. As the n(H₂O)/n(SiO₂) ratio was decreased from 1 500 to 500, the membrane thickness was increased from 1.7 μm to 10.8 μm. These results show that the membrane thickness could be easily adjusted mainly by varying the water content of the synthesis solution.

Key words: NaA, Zeolite, Zeolite membrane, Inorganic membrane