Preparation And Properties Of Poly(Aryl Ether Sulfone) Ultrafiltration Membrane Modified By Metal Organic Frameworks

Membrane separation techniques exhibit promise as safe,effective,and facile methods for wastewater treatment,and they can readily be applied in water-recycling systems.If appropriate membrane separation techniques are used,impurities in sewage can be removed,therefore,membrane separation techniques play a significant part in social development and environmental conservation.Membrane separation is considered to be economically feasible,and it provides several advantages,including excellent selectivity,high energy efficiency,and strong adaptability.Consequently,ultrafiltration（UF）has been widely used in wastewater treatment,food processing,biological separations,and other fields,and it can effectively remove colloids and macromolecules.UF membranes show immense potential for wastewater purification,and the selective permeabilities of membranes can protect water resources from natural organic matter.However,UF membranes also suffer troubles such as low filtration flux and membrane pollution.Membrane pollution reduces the permeation flux of the UF membranes,and it also severely compromises the separation performance.Therefore,modifications are required to reduce the degree of fouling and improve the service lives of membranes.Currently,there are several methods employed for modification of UF membranes,among which physical blending has proved to be an excellent and convenient method.Physical blending of UF membranes involves simple preparation methods for the introduction of hydrophilic nanomaterials,and they could intensify the anti-pollution performance of the membranes.In this work,firstly,the UF membrane was modified by physical blending modification method.In the first section of this work,the novel nanocomposite based on both nanoporous MOFs and hydrophilic carbon quantum dots（CQDs）was exploited for the fabrication of PES ultrafiltration（UF）membranes.CQDs were synthesized via pyrolysis of citric acid,and UiO-66-NH₂@CQDs were synthesized via the condensation reactions of CQDs and UiO-66-NH₂ using EDC and NHS as the condensating agents.The properties of resulting membranes on the porosity,membrane morphology,hydrophilicity,permeability and anti-pollution capability were adequately investigated.The membranes incorporated with UiO-66-NH₂@CQDs exhibited significantly improved water flux(up to 358.5 Lm^-2h^-1),which was～1.82 times that of pristine PES membrane.Additionally,the BSA rejection rates for the hybrid membranes all maintained above 95.0%.Furthermore,the hybrid membranes exhibited enhanced anti-pollution capability,and the highest flux recovery ratio（FRR）of the hybrid membrane with 0.5%UiO-66-NH₂@CQDs reached 77.6%.The membranes incorporated with UiO-66-NH₂@CQDs exhibited better permeability and anti-fouling performance than those only incorporated with CQDs or UiO-66-NH₂.This work reveals that the novel hydrophilic nanofillers combining CQDs and MOFs exhibit enormous potence for application in water treatment membranes.Furthermore,In the second section of this work,the novel nanocomposites based on both nanoporous MOFs and polyethyleneimine（PEI）were exploited as dopants and sulfonated polyethersulfone（SPES）as substrates for the fabrication of ultrafiltration（UF）membranes.UiO-66@PEI were prepared by PEI coated UiO-66 using EDC and NHS as binding agents.The resulting membranes were fully characterized,with data on the porosity,membrane morphology,hydrophilicity,and UF performance.The SPES membranes incorporated with UiO-66@PEI exhibited significantly improved water flux(up to 372 Lm^-2h^-1),which was～1.91 times greater than that of unmodified PES membrane.Additionally,the BSA rejection rates for the composite membranes all maintained above a level of 90%.Furthermore,the hybrid membranes exhibited intensified anti-pollution capability,and the highest flux recovery ratio（FRR）achieved to 82.11%with 0.5%content.The membranes incorporated with UiO-66@PEI exhibit better permeability and anti-fouling performance than do the membranes incorporated with UiO-66.This work reveals that the novel hydrophilic nanofillers PEI-coated MOFs exhibit great potential for application in water treatment membranes.To sum up,this paper fabricated a suite of UF membranes based on the metal organic frameworks and polyethersulfone materials,the results proved that the permeability and anti-pollution capability of the hybrid UF membrane were better than the initial PES UF membrane,and had a broad application prospect.