NaA zeolite membranes were prepared by secondary growth method on the outer surface of α-Al2O3 hollow fiber supports. Vacuum seeding method was used for planting zeolite seeds on the support surfaces. Hydrothermal crystallization was then carried out in a synthesis solution with molar ratio of Al2O3:Si O2:Na2O:H2O =1:2:2:120 at 100 °C for 4 h. Effects of seeding conditions on preparation of hollow fiber Na A zeolite membranes were extensively investigated. Moreover, hollow fiber membrane modules with packing membrane areas of ca.0.1 and 0.2 m2 were fabricated to separate ethanol/water mixture. It is found that the thickness of seed layer is obviously affected by seed suspension concentration, coating time and vacuum degree. Close-packing seed layer is required to obtain high-quality membranes. The optimized seeding conditions(seed suspension mass concentration of 0.5%–0.7%, coating time of 5 s and vacuum degree of 10 k Pa) lead to dense Na A zeolite layer with a thickness of 6–8 μm. Typically, an as-synthesized hollow fiber Na A zeolite membrane exhibits good pervaporation performance with a permeation flux of 7.02 kg·m-2·h-1and separation factor N 10000 for separation of 90%(by mass) ethanol/water mixture at 75 °C. High reproducibility has been achieved for batch-scale production of hollow fiber Na A zeolite membranes by the hydrothermal synthesis approach.
气升式纳滤装置是一种新型膜过滤装置,具有能耗低、过滤条件温和等优点,在生化产品的分离纯化中应用前景广泛。以杆菌肽水溶液为过滤体系,采用孔径为0.9 nm的TiO2陶瓷纳滤膜,系统考察了曝气量和跨膜压差对气升式纳滤装置过滤性能的影响。结果表明,曝气可有效提升通量和截留率;当跨膜压差为0.3 MPa时,曝气量由20 L h 1增大到100 L h 1,通量和截留率分别提升34.0%和14.5%,在曝气量100 L h 1时两者达到最大,进一步增大曝气量,通量和截留率开始下降;当跨膜压差为0.1、0.3、0.5 MPa时,对应的最优曝气量分别为60、100、140 L h 1。并通过模型计算,分析了不同操作条件下,气升式纳滤装置流体力学性质和能耗的变化情况。
