Preparation And Characterization Of Graphene Oxide Modified Polyamide Composite Nanofiltration Membrane

Traditional polyamide（PA）composite nanofiltration membrane,which is fabricated by interfacial polymerization of piperazine（PIP）and trimesoyl chloride（TMC）,has defects with low flux.In recent years,there are many researches have been done to improve the flux of PA composite nanofiltration membrane,such as adding a variety of nanoparticles,porous materials and nano lamella materials in PA functional layer.Although these works greatly improved the flux of the PA composite nanofiltration membrane,the salt rejection rate decline more or les.To sum up,this thesis aims to solve the "trade-off" phenomenon,that the flux increase while the rejection decrease.Due to the advantages of the structure and functional groups of graphene oxide（GO）,we choose GO as the nano lamella material to modify PA nanofiltration membrane in our study.Different from the previous GO-modified PA nanofiltration membrane,which was reported to add GO directly into the aqueous phase of interfacial polymerization,GO is acyl chlorided by Triphosgene（BTC）to improve reactive activity in our study.GO and acyl chlorided GO（GO-COCl）is characterized by means of FTIR,XPS element analysis,Transmission electron microscopy（TEM）and Atomic force electron microscopy（AFM）.The results showed that GO was successfully acyl chlorided,and the size and thickness of GO remain unchanged.Under the action of ethanol dispersant,a certain amount of GO-COCl was well dispersed into TMC-hexane solution as the organic phase,which react with PIP aqueous solution to prepare GO-COCl modified PA composite nanofiltration membrane.The surface chemical composition and structure,surface hydrophilic and morphology of membrane is characterized by XPS,FTIR,AFM and water contact angle test（WCA）and scanning electron microscopy（SEM）.The results show that GO-COC1 is immobilized into the PA functional layer by bonding with PIP,which provides a channel for the transmission of water.However,due to the introduction of ethanol,GO did not improve the hydrophilicity of the membrane surface.At the same time,the surface charge,permeability and thermal stability of the membrane were tested.The test results show that the addition of GO-COCl in PA function layer can increase the electronegative of membrane surface;0.002%GO-COCl and 2%ethanol can make PA/GO-COCl composite membrane reach the best performance;Compared with the traditional PA,water flux of PA/2GO-COCl doubled,while Na₂SO₄ rejection rate increase 2%;Increasing the operating temperature,the PA/2GO-COCI composite membrane has better thermal stability.