Preparation and characterization of thin-film composite polyamide nanofiltration membranes

Polyamide thin-film composite membranes were prepared by interfacial polymerization of 1,3-phenylene diamine(PDA)and trimesoyl chloride(TMC)on polysulfone(PSF)ultrafiltration membrane.The effect of interfacial polymerization conditions on the separation performance of composite membrane,and the composite membrane separation properties for different salt solutions were systematically investigated.The surface morphology and contact angle of the composite and substrate membranes were analyzed by atomic force microscopy(AFM)and contact angle measurements,respectively.The results show that the optimum polymerization conditions are as follows:the concentration of PDA is 1.5%(mass fraction),the concentration of TMC is 0.1%(mass fraction),the soaking time in aqueous phase is 3min,reaction time is 20 s,curing temperature is 80℃,curing time is 3min.The membrane prepared under the optimum conditions exhibited a rejection of 95.6%to 2 000mg/L MgSO4 aqueous solution,apure water flux of 7L/(m2·h)and a salt rejection order of Na2SO4MgSO4NaClMgCl2when tested under 0.6MPa.Moreover,the changes of morphology and contact angle showed that a polyamide active layer was formed on the substrate by interfacial polymerization.