添加聚合物中间层对NaA分子筛膜的合成与性能的影响

摘要

Zeolite NaA membranes were prepared on the outer surface of α-Al2O3 hollow fiber supports by secondary growth method.Dip-coating was used as seeding method.The influences of adding polyvinyl pyrrolidine (PVP) intermediate layer on membrane formation and its separation properties were investigated.The synthesized membranes were characterized by scanning electron microscopy (SEM).And the separation properties of the membranes were evaluated by pervaporation of 90％ ethanol/water mixture at 75 ℃.It is shown that the zeolite membrane prepared without PVP coating has a separation factor around 3 000 while the membrane prepared with PVP coating has a separation factor higher than 10 000 by using the dip-coating seeding method.The effect of the PVP coating amount on the flux of the as-synthesized membranes was also investigated.The membranes synthesized with PVP coatings (the separation factor was ＞10 000) had a lower flux compared to those synthesized without PVP coatings (dipcoating-wiping seeding method,the separation factor was＞10 000) [7.83 kg/(m2 · h)].With increasing the concentration of the PVP aqueous solution,the fluxes of the zeolite membranes correspondingly decreased,i.e.,the fluxes were 7.35,5.82 and 5.51 kg/(m2 · h) with PVP concentration of 1％,3 ％ and 5 ％ respectively.%采用浸涂法涂敷晶种,并通过二次生长法在α-Al2O3中空纤维外壁制备了NaA分子筛膜,考察了添加聚乙烯吡咯烷酮(PVP)中间层对成膜和膜分离性能的影响.采用扫描电镜(SEM)对膜的表面形貌进行表征,通过75℃渗透汽化分离质量分数为90％的乙醇/水溶液表征膜层的分离性能.研究发现,采用浸涂法涂敷晶种,无PVP中间层制备的膜层对乙醇/水溶液的分离因子仅为3 000左右,而添加了PVP中间层制备的膜层的分离因子可超过10 000.考察了PVP添加量对膜通量的影响.研究发现,添加了PVP中间层制备的膜(其分离因子＞10 000)的通量比无PVP中间层的膜(浸涂-滚擦法涂敷晶种,分离因子＞10 000)的通量[7.83 kg/(m2·h)]低,且随着制备中间层的PVP溶液浓度的升高,膜的通量相应降低,当PVP质量百分浓度分别为1％,3％和5％时,膜的通量分别为7.35,5.82和5.51 kg/(m2·h).