Preparation And Performance Of Zwitterionic Polyarylether Oxadiazole Modified Ultrafiltration Membrane

Polyarylether materials are widely used in the field of separation membranes due to the numerous excellent properties.The material can be dissolved in a variety of solvents and is suitable for preparation of ultrafiltration membrane by immersion precipitation phase transformation.However,due to their hydrophobicity,polyether materials are easy to be polluted by organics in water treatment,which severely limits the application of such membrane materials in water treatment.At the same time,zwitterionic polymers have good anti-pollution properties,so using zwitterions to modify ultrafiltration membrane materials is one of the effective ways to solve membrane pollution.In this article,a bisphenol monomer containing fluorene structure was designed and synthesized.Through low-temperature polycondensation and quaternization,a zwitterionic poly aryl ether oxadiazole(ZF-PAEO)containing fluorene structure was synthesized.The Infrared Spectroscopy(IR)and Hydrogen Nuclear Magnetic Resonance Spectroscopy(~1H-NMR)confirmed the chemical structure and composition of the obtained polymer,confirming the successful synthesis of ZF-PAEO.ZF-PAEO was then blended into commercial polyethersulfone resin with ZF-PAEO as an additive,and a series of zwitterionic modified ultrafiltration membranes were prepared by phase inversion method.Scanning Electron Microscope(SEM)and Atomic Force Microscope(AFM)were used to observe the changes of membrane structure.The water contact angle test showed that as the content of ZF-PAEO increased,the hydrophilicity of the membrane increased.After adding 0.5 wt%of ZF-PAEO,the contact angle of the membrane surface decreased from the initial 83.2°to 70.2°.The results of ultrafiltration membrane performance test experiments showed that the water flux of the membrane was increased after adding ZF-PAEO,the protein adsorption capacity was reduced,and the water flux recovery rate was also improved.When the content of ZF-PAEO was 0.5 wt%,The water flux recovery rate increased from the initial 77.01%to89.02%,which indicated that the anti-fouling ability of the zwitterionic modified membrane has been significantly improved.In the antibacterial test,the modified membrane also showed the performance of inhibiting the adhesion and growth of bacteria.In order to synthesize zwitterionic polymers more simply and improve their industrial application value,bisphenol monomer containing benzimidazole structure was further synthesized to prepare amphoteric poly aryl ether oxadiazole(ZB-PAEO)membrane containing benzimidazole structure.The chemical structure of the polymer was characterized by Fourier Transform Infrared Spectroscopy(IR)and Hydrogen Nuclear Magnetic Resonance Spectroscopy(~1H-NMR)to confirm the successful synthesis of ZB-PAEO.A series of zwitterionic modified ultrafiltration membranes were prepared by non-solvent induced phase separation process.Scanning Electron Microscope(SEM)and Atomic Force Microscope(AFM)were used to observe the changes in the microscopic membrane structure,and to characterize the water contact angle performance.The results showed that the ultrafiltration membranes had better hydrophilic properties after adding ZB-PAEO.After the addition of 3.2wt%ZB-PAEO,the water contact angle decreased to 45.5°.Cyclic ultrafiltration experiments showed that the water flux of the zwitterionic modified membrane was increased compared with the original membrane,the anti-protein adsorption performance was improved,and the water flux recovery rate was also increased.When the content of ZB-PAEO was 3.2 wt%,the water flux recovery rate reached 87.09%.At last,it was found in the bacteriostatic experiment that the modified membrane showed the property of inhibiting bacterial adhesion,which effectively improved the ability of resisting biological pollution of the membrane,and the modified membrane still showed stable separation permeability properties under long-term operation.