| Nanofiltration membrane is a kind of low-pressure-driven membrane with special properties,such as high retention of multi-valent ion salts and organic micro-molecular compound with molecular weight of 200-2000.Nanoflitration membrane separation technology is usually used for water softening and purifying, comparing with reverse osmosis(RO) process for desalination,and is widely applied in the industrial fields of environmental protection,wastewater treatment,food processing and so on.Nanoflitration membrane can be fabricated by means of various methods:phase-inversion process,blending method,chemical modified method, compositing method,including interfacial polymerization method which is the most widely used method to prepare nanofiltration membranes.The interfacial polymerization takes place at two-phases interface to form a nanometer-size polymer thin film on the surface of the supporting membrane,so as to obtain the thin-film composite(TFC) nanofiltration(NF) membrane.In the recent years,along with the developing attention paid to membrane technology,the interfacial polymerization(IP) technology for fabricating nanofiltration membrane makes a great progress.Various monomers-substrate systems are successfully applied to nanofiltration membrane preparation.Monomers in aqueous phase with bifunctional or tri-functionality are used widely owing to their easily available.Whereas monomers with polyfunctionality are applied to fabricate the TFC NF membrane for higher performance and special properties.Dendrimers,containing high-density terminal amine group which provides a large number of reactive sites,have received great attention.Polyamidoamine(PAMAM) acts as the most-studied dendrimer has been studied to be used for membrane modification.PAMAM dendrimer composite membranes were fabricated by in situ modification(IM) method by Kazama et al.to obtain high separation performance of CO2.Li et al.prepared the PEK-C NF membrane using PAMAM as monomer of the interfacial polymerization for purifying aqueous solution.In this work two novel TFC NF membranes,PAN/PAMAM composite nanofiltration membrane and PVDF/PAMAM composite nanofiltration membrane, were fabricated by interfacial polymerization using PAMAM and trimesoyl chloride (TMC) as monomers,PAN ultrafiltration membrane and PVDF ultrafiltration membrane as substrate.The membrane performances such as pure water flux, rejection of MgSO4,MgCl2,NaCl and PEG600 were studied.The morphology and chemical characterization of the membrane surface were also carried out by FTIR-ATR spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscope and atomic force microscope.The results showed that an ultra-thin dense layer was formed on the substrate.Under an operational pressure of 0.6-0.8 MPa, rejection of Na2SO4 and PEG600 for the composite nanofiltration membrane are higher than 90%,while rejection of NaCl is lower than 50%,which demonstrate that the composite nanofiltration membrane is a typical nanofiltration membrane.Additionally,the effects of interfacial polymerization conditions and operating conditions on the performance of composite membrane were investigated,including concentration of reactants,reacting time,curing temperature,operating pressure,salt concentration,pH value of feed solution.The optical preparation conditions of the PAN/PAMAM(1G) composite nanofiltration membrane were given as follow: 3.0×10-3 mol L-1 PAMAM(1G) in water,5.0×10-3 mol L-1 TMC in hexane,reacting time at 300 seconds at room temperature,curing temperature range from 20 to 80℃, and curing time at 15min.The optical preparation conditions of the PVDF/PAMAM(1G) composite nanofiltration membrane were given as follow: 5.0×10-3 mol L-1 PAMAM(1G) in water,5.0×10-3mol L-1 TMC in hexane,reacting time at 300 seconds at room temperature,curing temperature range from 80 to 120℃, and curing time at 15min.In addition,The physicochemical characteristics of PVDF/PAMAM composite nanofiltration membrane were also sutdied.The results showed that composite nanofiltration membrane had good resistance to acid-alkali, organic solvent resistance,chlorine and high temperature,and exhibit good long-term stability.
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