Preparation And Properties Of Zwitterionic Polyimide Ultrafiltration Membrane

Polyimide is a class of high performance engineering plastics synthesized from aromatic dianhydrides and diamine monomers.Due to its excellent thermal and dimensional stability,chemical resistance and mechanical strength,polyimide can meet some of the key requirements of an ideal membrane material.However,their inherent hydrophobicity has caused concern about insufficient wettability,which directly impairs the membrane’s permeability and stain resistance.Based on the excellent anti-pollution properties of zwitterionic polymers,a polyimide(P-PI)containing piperazine structure was synthesized,and a polyazide containing a bis-zwitterionic group was synthesized by quaternization reaction.Amine(ZP-PI).Anti-pollution ultrafiltration membrane was prepared by immersion precipitation induced phase inversion method using novel zwitterionic polyimide as membrane material.The chemical structure and composition of the obtained polymer were determined by infrared spectroscopy and nuclear magnetic resonance spectroscopy,and the thermostability of the obtained polymer was analyzed by thermogravimetry.The introduction of a zwitterionic group in the polyimide increases the hydrophilicity,and the surface of the film is changed from hydrophobic to highly hydrophilic.The results show that the zwitterionic modified membrane has obvious hydrophilicity improvement compared with the pure polyimide membrane,and can improve the adsorption of non-specific proteins.Static adsorption and dynamic cycle ultrafiltration experiments with bovine serum albumin(BSA)solution and soy protein(SPI)showed that the zwitterionic modified membrane has good anti-pollution ability,especially irreversible pollution ability,and has good anti-pollution.Performance and long-term stability.Among the separation performance,the ZP-PI membrane can maintain a protein retention rate of more than 90%while maintaining a water flux of 247 L/m2h.In addition,the water flux recovery rate of the zwitterionic modified membrane after three cycles of filtration of the BSA solution was 90.90%,while the water flux recovery rate of the control P-PI membrane was only 86.82%.These results demonstrate the superiority of zwitterionic modified membrane materials and provide a simple and scalable method for large-scale preparation of anti-pollution ultrafiltration membranes,which has potential application prospects.Biological contamination is one of the major problems in the membrane process of water treatment biotechnology.One of the anti-biofouling strategies is to construct the surface of the antibacterial membrane.Further experiments were carried out to prepare a novel imidazole group-containing polyimide(I-PI)and a zwitterionic polyimide containing an imidazole group(ZI-PI)by a novel synthesis method.The chemical structure of the polymer was analyzed by 1H NMR spectroscopy and Fourier transform infrared spectroscopy(FTIR).ZI-PI and I-PI films were prepared by a non-solvent induced phase separation(NIPS)process.ZI-PI and I-PI films were characterized by scanning electron microscopy(SEM),atomic force microscopy(AFM)and static water contact angle(WCA)measurements.The film exhibits excellent protein antifouling properties and significant surface hydrophilicity.Cyclic ultrafiltration experiments of protein solutions showed that the non-specific protein adsorption of the zwitterionic membrane,especially the irreversible protein adsorption,was significantly reduced,indicating excellent antifouling properties.In the bacteriostatic test,the I-PI membrane and the ZI-PI membrane showed an effect of inhibiting bacterial adhesion growth.The construction of hydrophilic antibacterial dual-function zwitterionic polyimide material is a feasible solution to improve the performance of polyimide ultrafiltration membrane.