The preparation of zeolite NaA membranes on the inner surface of hollow fiber supports

Zeolite NaA membranes with excellent water/ethanol separation factors are successfully prepared on the inner surface of hollow fibers in a rotating autoclave for the first time. NaA/PES composite hollow fibers (CHF) are first used to investigate the effects of different synthesis conditions such as synthesis composition, synthesis time and synthesis method (static and dynamic) because there are uniform seed crystals on the inner surface of CHF supports. The seeded growth of zeolite NaA membranes on the inner surface of alumina hollow fibers (AHF) supports (1.0 mm i.d.) are carried out at 373 K. The optimal synthesis conditions obtained are applied to AHF supports to investigate the effects of seed suspensions by the dip-coating seeding method. The effects of the synthesis conditions for AHF supports on the membrane morphology and properties are also investigated. The synthesized membranes are characterized by scanning electron microscopy. The separation properties of the membranes are evaluated by pervaporation of 90 wt.% ethanol/water mixture at 348 K. Zeolite membranes with high separation factor up to 10,000 can be obtained under the conditions: synthesis composition of 7.5Na2O:2SiO2:Al2O3:600H2O, synthesis time of 5 h, using a rotating autoclave (30 rpm).

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► Uniform seed layer can be obtained by adding clear solution to seed suspension.
► Clear solution can be easily generated from the synthesis solution.
► Clear solution can anchor seed particles to the support surface.
► Inner Zeolite membranes on hollow fibers can be successfully prepared.