Preparation And Antifouling Modification Of Novel Crown Ether Polymer Ultrafiltration Membranes

Ultrafiltration technology has functions such as separation,purification,and concentration,as well as features of high efficiency,energy conservation,and environmental protection.It has a good application prospect in the field of water treatment.With the development of membrane technology,traditional membrane materials have been unable to meet the requirements of membrane technology progress in terms of permeation separation and anti-fouling performance.The preparation of ultrafiltration membranes through non solvent induced phase separation（NIPS）has attracted widespread attention in the preparation of ultrafiltration membranes with good dimensional selectivity and excellent antifouling properties due to the unique phase separation structure of amphiphilic polymers due to the incompatibility of their hydrophilic and hydrophobic parts at the polymer water interface.Based on the above characteristics,the hydrophilic crown ether（dibenzo-18-crown-6-ether,DE）unit was introduced into the terphenyl and indigo polymers through the super acid catalytic polycondensation reaction to prepare the amphiphilic polymer for ultrafiltration permeability test,and the polymer was modified by adjusting the molecular structure and grafting to study its anti-fouling performance.Dibenzo-18-crown-6-ether,p-triphenyl and indigo polymers（PDTI10）were prepared by superacid catalysis.The results of nuclear magnetic resonance hydrogen spectroscopy（¹H NMR）and gel chromatography（GPC）confirmed that the polymer with good degree of polymerization was successfully synthesized.TGA and BET characterization results indicate that the polymer has good thermal stability and good pore structure.In addition,the amphiphilic polymer has good thermal stability and film forming performance,and the microphase separation during phase separation enables the ultrafiltration membrane to have relatively uniform pore size and excellent separation performance.The optimal flux of the ultrafiltration membrane reached 830.2 LMH bar^-1,and the corresponding BSA retention rate was 97.2%,which proved that the polymer material had excellent permeation-selectivity tradeoff.By increasing the content of crown ether monomer and grafting bromobutane on polymer,the hydrophilicity of polymer is increased,resulting in delayed phase separation of ultrafiltration membrane,and the cross-section structure of the membrane gradually changes from finger-like pore to loose sponge pore.Increasing the molar ratio of DE to p-triphenyl in the polymer can greatly improve the anti-fouling performance of the membrane.As the molar ratio of DE to p-triphenyl increased from 1:9 to3:7,the flux recovery（FRR）of the membrane increased from 58.5%to91.5%,and remained above 80.2%after three cycles.At the same time,the introduction of bromobutane also significantly improved the permeability and anti-pollution properties of ultrafiltration,and reduced the proportion of irreversible pollution in the cycling test of ultrafiltration membrane.The oxygen content of the membrane surface（18.62%）was higher than that of the polymer body（13.97%）,which confirmed the surface segregation of hydrophilic crown ether segment and bromobutane group in the copolymer.In conclusion,amphiphilic copolymers containing crown ether synthesized by one-pot polycondensation provide an effective way for the preparation and property regulation of ultrafiltration membranes.The systematic and comprehensive preparation and characterization of novel PDTI polymer membranes in this study provide insight into intrinsic micropores and antifouling ultrafiltration membranes.