| Nanofiltration membranes have attracted much attention in the field of water treatment due to their high permeability and low energy consumption.At present,polyamide nanofiltration membranes have been applied industrially.Under an oxidant-containing environment（sodium hypochlorite is used for sterilization and cleaning of membrane module）,the amide bond is easily degraded,resulting in a decrease in membrane separation performance and life span.In this study,nanofiltration membranes（NF）with excellent separation and oxidation resistance performance were prepared by the method of interfacial polymerization（IP）.Beta cyclodextrin（β-CD）/graphene quantum dots（GQDs）,phloroglucinol（Phg）and saccharide molecules were chosen as the aqueous monomer to prepare high-performance polyester nanofiltration membranes.The specific contents are as follows:High flux polyester nanofiltration membranes for dye separation were prepared by interfacial polymerization withβ-cyclodextrin（β-CD）as the aqueous monomer,graphene quantum dots（GQDs）as the additive and trimesoyl chloride（TMC）as the organic monomer.β-CD with abundant hydroxyl groups and GQDs with hydrophilic functional groups have similar size and good interface compatibility.They synergistically act on the surface of the membrane in the process of IP.A relatively loose and high-permeablity nanofiltration membrane was prepared.When the concentration of GQDs was 0.5 wt%,the pure water flux of theβ-CD/GQDs NF membrane reached 474.7 L/m2hbar.The dye rejection of Eriochome black T and Congo red remained above 93.0%.Theβ-CD/GQDs NF membranes were immersed in Na Cl O solution（10000 ppm）for 120 h,and the rejections rate of dye were basically unchanged.It has been proved thatβ-CD/GQDs NF membranes have excellent oxidation resistance.When the aqueous phase was regulated to alkaline environment,Phg was chosen as the aqueous monomer polymerizing with TMC.High-selectivity polyester membranes for desalination were prepared.With the concentration of Phg monomer increased,the surface chargeability was increased significantly,the surface hydrophilicity was enhanced,the polyester separation layer was denser,a wrinkle structure appeared on the surface of the membrane and the roughness was increased.When the concentration of Phg increased to 2.5 wt%,the flux of Phg-TMC NF membrane was 10.1 L/m2h（2bar）,and the rejection of Na2SO4 and Na Cl reached 96.7%and 53.3%,respectively.The Phg-TMC NF membranes immersed in Na Cl O solution（10 ppm）for 100 h,the rejections rate of Na2SO4 remained above 90.0%.It has been proved that Phg-TMC NF membranes have good oxidation resistance.Small molecules of natural saccharides（glucose（Gluc）,sucrose（Sucr）,raffinose（Raffin）andβ-CD）were selected as aqueous phase monomers polymerizing with TMC.The aqueous phase was regulated to alkaline environment by adding Na OH and the reaction temperature was increased during IP process.High-efficiency polyester nanofiltration membranes for desalination were prepared.Alkaline environment could activate the hydroxyl groups of saccharides molecules.The IP reaction was performed at a higher temperature,which promotes the diffusion of saccharide monomers into the water/oil reaction zone,thereby promoting the interfacial polymerization reaction and preparing a dense and defect-free polyester nanofiltration membrane.When the temperature of IP is 50 oC and the concentration of Na OH is 0.12 mol/L,the pure water permeability of the resultant Gluc（50）-TMC NF membrane is as high as 16.1 L/m2hbar,and the rejection rate of Na2SO4 is higher than 97%.The Gluc（50）-TMC NF membranes immersed in Na Cl O solution（100 ppm）for 140 h,and the Na2SO4rejections rate were basically unchanged.It has been proved that Gluc（50）-TMC NF membranes have good oxidation resistance. |
