Mechanistic study of zeolite membrane formation

Abstract

Recently, zeolite membranes have widely been used for the ethanol-water separation process, being developed in the form of thin films, deposited on porous supports. This work focused on the comparison of a NaA membrane synthesized on an a-Al2O3 upport using different techniques; conventional hydrothermal treatment, microwave hydrothermal treatment and electrophoresis. The microwave technique can be used to synthesize membrane in much shorter time than with other techniques. A comparison of circulated and static methods of microwave hydrothermal treatement effects pm tje ,pr[jp;pgu pf tje ,e,brame was a;sp omvestogated. The results showed that there is no difference in effects on morphology between the two methods. The effects of synthesis time, synthesis temperature, seeding time and seed suspension concentration on the layer growth development of the membrane in these cases were also considered. It was found that the zeolite membran can be synthesized in a shorter time at higher temperature. Seeding time and seed suspension concentration have the same effect on the seeding layer. The layer growth started from the semicrystalline formation, followed by the formation of hemispere-shaped grains, and finally the growth process of cubic morphology, whigh is a fully crystalline layer. The formation of as-synthesized membranes is discussed according to observations by SEM and XRD.