Study On The Structure Adjustment And Performance Of Cross-Linked Polyimide-Based Separation Membrane

Polyimide has become a popular material in the field of separation membrane research due to its good heat resistance,solvent resistance and easy crosslinking.In this paper,based on the commercial model of Lenzing P84 polyimide,P84/GO mixed matrix film and P84/GO laminated composite film were prepared.The polyimide contains a large number of amide groups,and can undergo an amidation reaction with the carboxyl group in bilirubin,so polyimide is used as a bilirubin adsorbent.First,multi-layer graphene oxide?GO?was used as a P84 casting solution additive to prepare a P84/GO mixed matrix film to improve the overall performance of the polyimide film,and triethylenetetramine?TETA?was used to crosslink the film To improve the solvent resistance of the membrane.The effect of GO content on membrane morphology and separation performance was studied.The results show that the mixed matrix membrane prepared by adding2 wt%GO to the 18 wt%P84 casting solution has a 100%rejection rate of gentian violet at 0.1MPa,and the flux is as high as 118 L/m²h.After the cross-linked membrane was immersed in N,N-dimethylformamide?DMF?,acetone and methanol solvent for 18 consecutive days,the overall performance of the membrane did not decrease and showed excellent solvent resistance.The membrane also has good heat resistance.When the membrane is operated at 80?,the rejection of the membrane does not decrease,and the membrane flux increases to four times the flux measured at 20?.Using the layered structure of GO,P84/GO laminated composite membrane was prepared by pressure filtration method.Taking P84 membrane with polyester nonwoven fabric support as the composite membrane base membrane,the separation performance of the membrane is improved by adding nano-alumina?Al₂O₃?,chitosan and other substances to GO.Adding 10wt%Al₂O₃ to the GO dispersion significantly increased the flux of the composite membrane.At a room temperature of 0.2 MPa,the composite membrane has almost zero rejection of sodium sulfate?Na₂SO₄?and magnesium chloride?MgCl₂?,and maintains a rejection rate of more than 99%for gentian violet and Congo red,and a rejection rate of 77 for methyl orange%,The membrane flux is 96L/m²h.The flux of the composite membrane prepared on the P84base membrane without nonwoven fabric support will be significantly reduced.The composite membrane obtained by adding 10 wt%chitosan to GO has a membrane flux of 3.07 L/m²h at room temperature of 0.2 MPa The rejection rates of Na₂SO₄ and MgCl₂ were 56.7%and 23.2%,respectively,and the rejection rates of Congo red,gentian violet and methyl orange were all above 99%.The polyimide affinity membrane was prepared by P84 and different additives through phase inversion method.By grafting polyethyleneimine?PEI?containing multiple amino groups onto the membrane,it is used for further amidation reaction with bilirubin carboxyl group.Organic additive polyvinylpyrrolidone?PVP?and inorganic additive lanthanum strontium cobalt iron?LSCF?nanoparticles are added to improve membrane performance.The effects of polyamide concentration and additive content on bilirubin adsorption were studied in detail.PEI modified polyimide membranes are used to prepare affinity membranes.The resulting membranes have many ligands and provide many active sites for the adsorption of bilirubin.When the content of polyimide is fixed at 14 wt%,both organic additives and inorganic additives can significantly change the morphology of the membrane and improve the adsorption of the membrane.When 5 wt%PVP content was 5 wt%and bilirubin concentration was 0.1 mg/mL,the static adsorption capacity of the affinity membrane at 25?was 15.1 mg/g and the dynamic adsorption capacity was 4.4 mg/g.