Study On The Adsorption Of Antibiotics By Metal-organic Frameworks

Antibiotics have been used for nearly a hundred years.Although antibiotics can effectively prevent and treat some diseases,most of them cannot be completely metabolized in the body of living things.Most of them are discharged into water in the form of active drugs or active metabolites,resulting in water environmental pollution.At present,the problem caused by excessive use of antibiotics has attracted worldwide attention.Therefore,how to quickly and effectively remove antibiotics from water has become an urgent problem to be solved.Compared with traditional porous materials（such as activated carbon,zeolite and molecular sieve）,metal-organic frameworks（MOFs）materials have the advantages of large specific surface area,easy adjustment of pore structure and many active sites for adsorption,etc.,and are widely used in adsorption separation,catalysis,controlled release of drugs and other aspects.In this paper,UIO-66 and MIL-101 are used as the basic materials,and amino,molecular imprinting technology and carbon foam are used to modify them,so as to realize that they can efficiently and selectively remove antibiotic molecules in water.At the same time,using x-ray diffraction（XRD）,scanning electron microscope（SEM）,transmission electron microscopy（TEM）,fourier-transform infrared spectroscopy（FTIR）,specific surface area analyser（BET）,thermogravimetric analysis-differential scanning calorimetry（TG-DSC）,raman spectroscopy（Raman）,high-performance mercury injection apparatus（MIP）and x-ray photoelectron spectroscopy（XPS）on the preparation of the materials were characterized by,in order to understand the material microstructure,physical properties and chemical composition and explore the mechanism of adsorption.The specific research results are as follows:1.A series of adsorption materials with different amino ratios,Ui O-66-NH₂（n）,were successfully prepared by changing the ratio of organic ligands to remove norfloxacin（NOR）and tetracycline（TC）from water.Ui O-66-NH₂（0.5）had the best adsorption performance for NOR and TC,and its adsorption process is more in line with pseudo-second-order kinetics and Langmuir adsorption isotherm model.In particular,its adsorption rate on NOR was extremely fast,which can reach adsorption equilibrium within 10 min.Meanwhile,the fitting results of Langmuir adsorption isothermal model show that its maximum adsorption capacity reached 673 mg/g.Moreover,the results of the selective adsorption experiment proved that the selective adsorption of NOR and TC could be realized by simply adjusting pH.In addition,by analyzing the FTIR and XPS before and after adsorption,the adsorption mechanism of UIO-66-NH₂（0.5）on NOR and TC mainly includes electrostatic attraction,ion exchange andπ–πconjugation.2.Molecularly imprinted MOFs（MI-MOF）materials were prepared following an in-situ template self-assembly strategy.The XRD and SEM analysis results indicate that the introduction and elution of template molecules had little effect on the crystal structure and surface morphology of the base MOF materials.The selective adsorption experimental results show that MI-MOF had excellent selective adsorption performance for NOR,and the presence of smaller competing analogues did not significantly influence the specific effect of the MI-MOF.This indicates that the selectivity of MI-MOF is not only attributed to the pore size,but also the active sites exposed on the surface of defects,which can have specific recognition ability for certain structural groups on the template molecules.The experimental results showed that the adsorption of NOR by MI-MOF was more in line with pseudo-second-order kinetics and Langmuir model.Moreover,when pH=7,the adsorption effect was the best,with the maximum adsorption capacity reaching 668 mg/g.By analyzing the FTIR and XPS spectra of the adsorbents before and after adsorption,it can be concluded that the main NOR removal mechanisms are electrostatic attraction,π-πconjunction,the Lewis acid-base reaction of Fe-OH with NOR,and Fe-O complexation.Therefore,the MI-MOF synthesised by in-situ self-assembly have great potential in future industrial applications due to their simple preparation process,excellent adsorption efficiency,significantly higher adsorption capacity,and excellent selective adsorption ability.3.In summary,hierarchical NH₂-MIL-101/CF and MI-MOF/CF have been successfully prepared by solvent thermal method and molecular imprinting technology for highly efficient NOR sequestration from the aqueous solution.The adsorption rate of NH₂-MIL-101/CF and MI-MOF/CF is significantly increased due to the existence of the hierarchical porous structure.MI-MOF/CF exhibits excellent adsorption capacity towards NOR,and the maximum adsorption capacity are determined to be 456 mg/g.Moreover,compared with NH₂-MIL-101/CF,MI-MOF/CF has a better selective adsorption performance.This selectivity is not only the selection of pore size,but also the active sites exposed on the surface of defects can have specific recognition ability to some special structural groups of template molecules.FTIR and XPS analysis reveal that the main adsorption mechanism isπ-πconjunction,ion exchange,Fe-O complexation and the Lewis acid-base reaction of Fe³⁺with NOR.In addition,the composite materials can easily realize solid-liquid separation and have good reusability,which have great value for industrial application.Consequently,this study will open up a worthy direction for the efficient and selective removal of macromolecular pharmaceuticals,and provide a new idea for the design and synthesis of MOFs.