沸石/聚酰胺反渗透复合膜的制备

Preparation of zeolite/polyamide nanocomposite reverse osmosis membrane

为了提高反渗透膜的通量,通过在界面聚合反应过程中添加NaA型纳米沸石分子筛制备了沸石/聚酰胺反渗透复合膜,采用SEM及复合膜性能测试的方法比较了沸石分子筛添加在水相或者油相中时对膜结构及分离性能的影响。SEM图谱结果表明:沸石分子筛添加在油相中时,沸石在聚酰胺基质中分散均匀,膜结构比较均一;但当沸石分子筛添加在水相中时,复合膜截面呈现双层结构,表层为聚酰胺层,沸石镶嵌在膜的底层,膜中存在孔洞。膜分离结果显示沸石分子筛添加在水相中时,复合膜的通量明显增加,但截留率下降。而沸石分子筛在油相中时复合膜的通量和截留率均增加。因此,沸石分子筛添加在油相中有利于膜分离性能的提高,当油相中沸石质量分数为0.1%时,膜通量增加为聚酰胺膜通量的2倍,同时截留率提高到了98%。

In order to improve the flux of the reverse osmosis membrane,zeolite/polyamide thin film nanocomposite（TFN） reverse osmosis membranes were fabricated by interfacial polymerization in the presence of NaA zeolite nanocrystals.The effects of introducing the NaA zeolite nanocrystals in the aqueous phase or the organic phase on the membrane morphology and desalination performance were investigated by means of SEM.According to SEM morphologies,the zeolite is embedded throughout the whole polyamide layer when zeolite is added into the organic phase,with a uniform structure.However,when zeolite is added into the aqueous phase,there are some macrovoids in the TFN membranes and the membranes have a two-layer structure,i.e.a polyamide surface layer and a zeolite sub-layer.When zeolite is added into the aqueous phase,the flux of the TFN membrane increases,whereas the salt rejection decreases clearly with the increase of the zeolite loading.However,when zeolite is added into the organic phase,both flux and salt rejection of the membrane are improved.Therefore,adding zeolite in the organic phase is good for improving the membrane performance.The flux is doubled and the rejection is increased to 98% when the zeolite mass fraction exceeds 0.1% in organic phase.