Thin Film Composite Nanofiltration Membrane Prepared On Polyetherimde Support

Nanofiltraion(NF)is a pressure-driven membrane with a molecular weight cut-off bewtten 200-1000 Da.Benefiting from the advantanges of low operation pressure,low temperature demand and high separation efficiency,nanofiltration membrane is widely utilized in petroleum,chemical industry,pharmaceutic,water treatment and other fields.However,the trade-off effect that meets in the membrane preparation process is difficult to break through and the high permeate flux is always obtained at the expense of the rejection.In addition,the traditional nanofiltration membrane used in the water system is difficult to apply in organic separation system,and the traditional method to fabricate the solvent resistant nanofiltration membrane is complicated.Therefore,simplifing the preparation process of organic solvent NF membrane is far of significance.Aim at the above problems,this paper will improve the membrane performance from the aspects of structure and echnology.(1)High flux poly(amide-co-ester)NF membrane is prepared by two times interfacial polymerization(IP)method with glucose as monomer.Via the second-IP,the glucose molecule inserted into the unstable polyamide structure prepared by the first-IP.Compared with the original polyamide NF membrane,the flux of the poly(amide-co-ester)NF membrane increases by 4 times and the rejection to glucose remains stable,thus the trade-off effect is weak.For the optimized NF-2G membrane,the rejection to small organic molecular glucose is 92.3% and the flux is 42.5 L m-2 h-1 at an operation pressure of 1.0 MPa.Characterized by SEM,AFM,DBES,ATR-FTIR,XPS,Zeta potential,etc.,it is indicated that poly(amide-co-ester)skin layers with crosslinked structure,which shows enhanced diffusion property,is generated by the interfacial polymerization occurs among TMC,G monomer and the terminal amine groups on the C-PEI support.The NF-2G membrane shows a rejection of 94.5% for Na2SO4 and a rejection as high as 100% for anion dye acid orange.Then NF-2G membrane has a good antifouling performance and the flux recovery rate can reach 99.4%.Therefore,the poly(amide-co-ester)NF membrane has the potential application in dye decolorization.(2)A high flux organic solvent composite NF membrane has been fabricated by a simplified method by combining the crosslinking and impregnation of IP diamine monomer in one step with polyethylenepolyamine(PEPA)as a crosslinker.Characterized by SEM,ATR-FTIR,XPS,DBES,etc.,it is demonstrated that TMC has a limiting effect on the membrane separation performance.The filtration test shows that the as-prepared composite membranes have good performance for dyes and antibiotics.At an operation pressure of 0.4 MPa,the optimized NF membrane prepared via the simplified method shows a rejection of 99.9% for 70 ppm Rose Bengal(RB)methanol solution with a flux of 7.8 L m-2 h-1,while a rejection of 91.7% for 30 ppm tetracycline methanol solution with a flux of 9.0 L m-2 h-1.Therefore,the simplified method is a feasible method to prepare a NF membrane with good performance.The simplified method can not only save the amount of time,water and amine in the membrane prepration precess,but can prepare a high flux organic sovlent NF membrane for methanol system.