| Pharmaceuticals and personal care products(PPCPs)are emerging pollutants that bring a series of risks to the ecological environment,especially the water system.Traditional wastewater treatment process is not satisfactory in removing of PPCPs,thus it is urgent to develop efficient and thorough new treatment methods.Due to their unique structure,metalorganic frameworks(MOFs)possess high porosity,high specific surface area,multi-functional ligands and abundant unsaturated metal sites,so that they can exhibit excellent performance in water pollution purification.However,the form of nanocrystalline particle faces the problem of agglomeration,and is hard to be separated and recycled after usage,which hindered the practical application.Combining MOFs with nanofiber substrate is a feasible choice to facilitate separating.In this work,a series of multi-functional fiber/MOFs composites were prepared by combining different electrospun oxide nanofibers with various ligands.Firstly,zirconia fiber membrane with excellent stability and good affinity for MOFs was selected as the substrate,and the water-stable UiO-66 was combined with it to obtain a composite membrane that can quickly adsorb antibiotics and arsenite.Due to the good mechanical properties and selfsupporting structure,the composite membrane can also dynamically remove contaminants from water.On the basis of the efficient separation of pollutants from solution by adsorption and filtration,we hope to achieve complete decomposition of pollutants with the help of advanced oxidation technology.In the second work,a layer of cobaltous dihydroxycarbonate was firstly prepared on the surface of zirconia fiber film via hydrothermal method,and then the composite was added into a solution with iron source.ZrO2/Fe-Co PBA composite material with high load was prepared by self-sacrificing template method,and could completely degraded NRF within 20min.Compared with traditional hydrothermal method,in-situ conversion method creates more Fe(Ⅱ)sites with higher catalytic activity during the preparation process,while the composite has good water stability and cycling stability,can be used in a wide pH range and achieve considerable degradation efficiency.Based on this work,we hope to prepare a fiber that can be used as a metal source for MOFs without surface modification,and directly undergo insitu conversion reactions on its surface.A variety of Fe3O4/MILs composite fibers with magnetic separation characteristics were obtained by in situ one-step hydrothermal method.Continuous seamless MOFs nanolayers were obtained on the fiber surface without adding additional metal sources during the preparation process,so that the MOF particles that are easy to agglomerate under normal circumstances could be evenly dispersed.The catalytic efficiency and recycling performance were improved.Specific work contents are as follows:(1)By solvothermal method,the metal-organic skeleton material UiO-66 with excellent water stability was loaded onto the electrospun zirconia nanofiber film,and a recyclable composite film material suitable for the adsorption and dynamic removal of a variety of pollutants was prepared.As a substrate,zirconia fiber has a suitable equipotential point,which makes carboxylic acid groups more easily anchored to bond on its surface,and effectively improves the loading capacity and bonding strength of MOFs composite.The maximum adsorption capacity of the composite membrane was 59.27 mg g-1 for tetracycline and 143.95 mg g-1 for arsenite,and the dynamic removal efficiency of tetracycline and arsenite was over 90%and 80%,respectively,at a high flux of 60 L/(m2·h).Experimental characterization and density functional theory(DFT)calculation were used to further explore the adsorption mechanism of UiO-66 on pollutants.Hydrogen bond and ligand exchange were the main driving forces of adsorption,and Zr-O bond played an important role in this process.Five cycles of filtration and desorption were carried out,the removal efficiency of TC and arsenite decreased to 70.9%and 80.1%of the initial efficiency,respectively,which still retained remarkable removal rate and the microstructure of the composite nanofibers remained basically unchanged.(2)A layer of basic cobalt carbonate was grown on the surface of zirconia fiber film by hydrothermal method,and a metallic iron source was added into the solution.The ZNS@FeCo PBA composites with high loading capacity were prepared by sacrificial template method.X-ray diffraction(XRD)and Fourier transform infrared(FT-IR)spectroscopy results showed that the characteristic peaks corresponding to basic cobalt carbonate disappeared completely after hydrothermal reaction,indicating that the transformation is complete.The proportion of Fe(II)site in ZNS@Fe-Co PBA is higher than that in PBA powder,which may be conducive to the improvement of catalytic performance.By introducing the second phase metal ions,the catalytic efficiency of the composite was further improved,and NRF could be completely degraded within 20 min.XRD,FT-IR spectrum and X-ray Photoelectron Spectroscopy(XPS)were used to compare the relationship between hydrothermal PBA powder and in situ ZNS@Fe-Co PBA in terms of crystal phase,element composition and valence.The results showed that ZNS@Fe-Co PBA prepared by in-situ method had better crystallinity and purity,and more initial Fe(Ⅱ)sites.This may be more conducive to the improvement of catalytic efficiency.The effects of PMS dosage,initial NRF concentration,pH value and co-existing anions on the degradation rate of NRF were studied.The results of free radical capture experiment and electron spin resonance(ESR)spectroscopy characterization showed that active oxygen species such as sulfate radical,hydroxyl radical,superoxide radical and singlet oxygen contributed to NRF degradation.(3)A series of electrospun Fe3O4 nanofibers(FNS)/MIL-88B,FNS/MIL-88A and FNS/MIL-100 composites were prepared by in-situ method.The composite had a high MOFs load,a saturation magnetization of 20 emu/g,and can be quickly separated under the application of an applied magnetic field.The effects of various reaction parameters on the conversion of MOFs were studied.The conversion of MOFs occurred completely on the surface of the fiber,but did not produce free MOFs grains in the solvent.The addition of a small amount of deionized water is essential for the nucleation growth of MOFs,but the addition of excessive water would lead to excessive growth of MOFs and fiber comminentation,affecting the quality of the finished fiber.In addition,the MOFs growth effect of Fe3O4 fiber was significantly better than that of Fe2O3 fiber,indicating that the type of metal source also affects the conversion rate of MOFs.The adsorption and catalytic properties of the three FNS/MILs composite fibers for NRF were compared,and FNS/MIL-88B showed the best performance,the maximum adsorption capacity was 214.09 mg g-1,and 98%of NRF could be degraded within 60 min.The catalytic mechanism of FNS/MIL-88B was studied by free radical capture experiment,FT-IR spectrum,ESR spectroscopy and XPS.It was found that Fe site was the active site of the reaction,and ·OH was the main reactive oxygen species. |
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