Preparation and Characterization of NaA Zeolite Membranes on Inner-surface of Four-channel Ceramic Hollow Fibers

High-performance NaA zeolite membranes were prepared on inner-surface of four-channel ceramic hollow fibers by combined counter-diffusion vacuum seeding and dynamic hydrothermal synthesis method. The as-prepared membranes were adopted to the pervaporation dehydration of 90wt% ethanol/water mixture at 75℃. Effects of seeding and synthesis conditions on morphology and separation performance of the membranes were extensively investigated in terms of flow rate of seed suspension, seeding time and synthesis temperature. These results showed that dense and uniform NaA zeolite membrane was obtained when the flow rate of seed suspension was 100 mL/h and the seeding time was 5 s. Over slow flow rate of seed suspension or too long seeding time increased the membrane thickness but generated defects on membrane surface simultaneously. When the NaA zeolite membrane was hydrothermally synthesized at 100℃ for twice, the membrane achieved the best water/ethanol separation factor of 1585 while the permeation flux was 8.8 kg/(m²·h) in the pervaporation dehydration. Lower synthesis temperature led to incomplete membrane crystallization and some defects were observed on the membrane surface. With excessive synthesis temperature defects were also detected in the cross-section of the membrane due to the over rapid crystallite rate, which resulted in poor separation performance of the membrane.