Preparation And Application In Water Treatment Of The Functional Composite Membranes Based On The Metal Organic Framework ZIF-8

Metal organic frameworks(MOFs)are porous materials formed by bridging metal ions and organic ligands.MOFs were gradually applied to membrane separation due to their large specific surface area and adjustable pore structures.As a kind of MOFs,ZIF-8 has the advantages of excellent thermal stability,chemical stability,simple synthesis conditions and so on,so it has a great prospect in the application of membrane separation.The inherent hydrophobicity of ZIF-8 could limit the permeance of separation membranes.In order to improve the hydrophilicity of ZIF-8,The cheap and accessible natural polyol tannic acid was used to modify ZIF-8 in this article.Then the hydrophilic ZIF-8 nanoparticles(T-ZIF-8)were introduced into the polyamide layer by interfacial polymerization to prepare the hydrophilic ZIF-8 thin film nanocomposite(TFN)reverse osmosis(RO)membranes.The morphology and physicochemical properties of T-ZIF-8 and TFN RO membranes were characterized by SEM,XRD,FTIR and other characterization methods.The performance of membranes was also tested.The experimental results showed that when the addition amount of T-ZIF-8 was 0.005w/v%,the flux of the TFN RO membrane was 1.5 times of that of the RO membrane without T-ZIF-8 while the rejection to NaCl maintained at 99.6%.ZIF-8 membrane often has the problem of weak adhesion between ZIF-8 nanoparticles and the substrate.In this paper,ZnO particles were added into the casting solution to prepare ZnO-Al2O3 hollow fiber hybrid membrane.ZIF-8 membranes were in situ synthesized on the outer surface of hybrid membranes by ZnO induction method to enhance the binding force between ZIF-8 and the substrate.The influence of ZnO content on the hybrid membranes was also investigated.On this basis,ZIF-8/SA composite hollow fiber membranes were prepared for dye separation.A series of characterizations and testing methods were used to characterize and test the membranes prepared at every stage.The experimental results showed that the composite membranes prepared on the ZnO-Al2O3 hollow fiber hybrid membrane spun by adding 10%ZnO had the best performances both in permeance and rejection.