Study On Preparation And Performance Of ZIF-8 Loaded Polyamide Reverse Osmosis Composite Membrane

In recent years,nanoparticles have been incorporated into polyamide(PA)to produce a thin film nanocomposite(TFN)membrane,which has become an advanced technology for the preparation of reverse osmosis membranes.Zeolitic imidazolate framework(ZIF-8)is a new type of porous material.The presence of organic ligands in the structure makes it well compatible with the organic membrane matrix.Therefore,ZIF-8 were used to modify the polyamide reverse osmosis composite membrane and the ZIF-8 and its particle size were investigated for the appearance,structure,penetration and antifouling performance of the reverse osmosis membrane.In this paper,qualitative and quantitative analysis of two kinds of synthesized nanomaterials were performed firstly.The membrane prepared by interfacial polymerization(IP)method was used to analyze the loading of the two different particle size ZIF-8.Finally,using disinfection by-products(DBPs)as target contaminants,the influence mechanisms of various factors on the removal rate were investigated.The actual water body was used as the background water distribution,and the effect of coagulation + microfiltration + modified membrane on the removal of DBPs was investigated.The particle sizes of the two ZIF-8 nanoparticles synthesized in this experiment were 50 nm and 500 nm,belonging to the microporous structure and providing a fast channel for water molecules.The addition of ZIF-8 nanoparticles results in the decrease of the surface roughness of the membrane,the decrease of the degree of cross-linking,and the increase of the hydrophilicity of the surface.When the particle size is smaller(50 nm),the hydrophilicity of the membrane surface increases more significantly and the particle size is smaller.At large(500 nm),the decrease in surface roughness is more pronounced.With the increase of the amount of ZIF-8 added,the water flux and salt rejection of ZIF-8/TFN increased continuously compared with polyamide reverse osmosis membrane(TFC).When the addition amount is(0.4w/v%),the water flux increases by about 65%.The salt retention rate remained above 98%.When the particle size is small(50nm),the increase in water flux and salt rejection is more significant.When the particle size was large(500 nm),the membrane was resistant to contamination.The performance improvement is even more significant.The removal rate of DBPs from the modified membranes was higher than that of pure membranes and commercial membranes.Within a certain range,the DBPs' molecular weight and molecular volume increased,the temperature decreased,and the p H increased.DBPs removal rate increased.In the actual water body water distribution experiment,the combination process of coagulation + microfiltration + modified membrane can better increase the removal of DBPs,and through coagulation can improve the membrane fouling during reverse osmosis.