Preparation And Study Of PEO Hydrophilic Polyamide Nanofiltration Membrane

Nanofiltration(NF),as a pressure-driven membrane separation process,has been a hot spot over the last decade.But,it’s difficult to restore the membrane original performance once the membrane has been fouled irreversibly.Therefore,improving the antipollution performance of membranes has been an essential tendency recently.It is well-known that hydrophilic polymers with ether oxygen groups are widely used in the separation membrane due to their very high antifouling property.The specific research contents and results are as follows.Novel flat-sheet thin-film composite nanofiltration membranes were fabricated through interfacial polymerization of O,O’-Bis(2-aminopropyl)polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol(Jeffamine)with ether oxygen groups as aqueous monomer and 1,3,5-Benzenetricarbonyl trichloride as organic monomer on porous polysulfone support membrane.Attenuated total reflectance Fourier transform infrared spectroscopy(ATR-FTIR),x-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM)and contact angle measurement were employed to characterize the chemical structures and morphologies of the membranes.The effects of preparation parameters including relative molecular weight of Jeffamine,pH of aqueous phase,concentrations of the organic and aqueous phase,reaction time,curing temperature,and curing time,on membrane performance were investigated.Under the optimum conditions,the rejection of MgSO4 solution is 45%and the pure water flux is 50 L/m2/h for the composite membranes,that is to say,the separation performance is to be improved.It is found that the antifouling effect is limited by humic acid and bovine serum albumin in the test.In order to improve the permeation-separation performance of the composite membrane,we investigated the influence of support membrane to Jeff-TMC composite membrane by changing the weight fraction of PSf.On the other hand,Jeff/PIP-TMC、Jeff/MPD-TMC and TAEA/Jeff-TMC composite membrane are obtained by incorporation of other types of amine monomer such as piperazine,m-phenylenediamine and tris(2-aminoethyl)amine in the interfacial polymerization.The results show that the separation performance can be improved but the flux can be decreased as the relative content of Jeffamine decreased.In order to improve the antifouling property,a second interfacial polymerization is carried out between Jeffamine and unreacted acyl chloride groups to establish double-layered poly(ethylene oxide)(PEO)hydrophilic structure on the nascent polyamide membrane.The surface morphology of the composite membranes are changed and the roughness is increased after the interfacial polymerization.After a second interfacial polymerization,the cross-sectional morphology is almost unchanged.Surface characterization by zeta-potential measurements and water contact angle measurements evaluate the charge properties and hydrophilicity of PEO-functionalized active layer,respectively.The membrane with double-layered PEO hydrophilic structure was more hydrophilic than that nascent polyamide selective layer without the decrease in pure water flux and rejection and had a higher antifouling performance.