| With the continuous progress of social science and technology,antibiotics are widely used in human disease treatment and diagnosis,aquaculture,food processing and other fields,leading to a large number of antibiotics into the water ecological environment,causing serious damage and pollution to the water body,and indirectly have adverse effects on human health.Therefore,the research and development of efficient removal of antibiotic pollutants in water has become the forefront and hotspot of environmental research,with profound social value and significance.Metal organic framework materials（MOFs）have obvious advantages in adsorption and removal of antibiotics such as diverse structures,simple synthesis methods,various types,large specific surface area and easy functionalization,etc.Therefore,this paper took MIL-53（Fe）as the basic material,prepared derivatives through functionalization,compounding,doping,calcining and other steps,and systematically studied the removal behavior and mechanism of MIL-53（Fe）based adsorbents on tetracycline antibiotics（tetracycline,oxytetracycline,aureomycin and doxycycline）in water.In this study,functionalized derivatives such as NH2-MIL-53（Fe）,NO2-MIL-53（Fe）and Br-MIL-53（Fe）were synthesized based on MIL-53（Fe）.The behavior and mechanism of functionalized MIL-53（Fe）used as adsorbents to remove tetracycline antibiotics in water were compared and analyzed.The results showed that the functionalized MIL-53（Fe）had better adsorption performance than the original MIL-53（Fe）,and Br-MIL-53（Fe）had more obvious respiratory characteristics,and the maximum adsorption capacity of tetracycline in water was309.6 mg g-1.The fitting degree of static adsorption experiment data with pseudo-second-order kinetic model and Langmuir model is high,indicating that the adsorption process is monolayer chemical adsorption.Thermodynamic studies show that the adsorption process is spontaneous and endothermic.π-πbond interaction is the main adsorption mechanism of functionalized MIL-53（Fe）for tetracycline.In addition,hydrogen bonding exists between NH2-MIL-53（Fe）and tetracycline,and acid-base interaction exists between NO2-MIL-53（Fe）and tetracycline.The functionalized MIL-53（Fe）in this study provides a feasible strategy for the removal of tetracycline in water and broadens the application range of MOFs as adsorbent.（chapter 2）In this study,MWCNT/MIL-53（Fe）composite materials were synthesized by simple chemical method based on MWCNT and MIL-53（Fe）materials.The adsorption and removal of tetracycline,oxytetracycline and chlortetracycline by composite materials were studied.And the reuse and stability of MWCNT/MIL-53（Fe）composites are also analyzed.A series of characterization showed that the introduction of MWCNT had no significant effect on the crystal structure and microstructure of MIL-53（Fe）material.The BET specific surface area,pore volume and pore size of MWCNT/MIL-53（Fe）composite were increased and its thermal stability was enhanced after modification by MWCNT/MIL-53（Fe）,which was conducive to adsorption and removal of pollutants in water.The experimental results showed that the adsorption data of tetracycline,oxytetracycline and chlortetracycline were well fitted with the pseudo-second-order kinetic model and Langmuir model.At the initial pH value of 7.0 and temperature of 25°C,the maximum adsorption capacity of MWCNT/MIL-53（Fe）composites for tetracycline,oxytetracycline and chlortetracycline was 364.37,325.59 and180.68mg g-1,respectively,which was 1.25,8.28 and 3.34 times that of MWCNT for antibiotics.The order of adsorption of MWCNT/MIL-53（Fe）composites was:tetracycline>oxytetracycline>chlortetracycline,which was mainly determined by the molecular weight of the antibiotic.In addition,π-πbond interaction plays an important role in the adsorption process.MWCNT/MIL-53（Fe）composite material has good reusability and water stability,and has potential application prospect in removing tetracycline antibiotics in water.（chapter 3）Based on the above research,MWCNT/NH2-MIL-53（Fe）composite material was synthesized by combining the advantages of the above two adsorption materials.The behavior and mechanism of the composite material and biochar adsorption to remove tetracycline and chlortetracycline from water were compared,and the reusability of MWCNT/NH2-MIL-53（Fe）composite material was analyzed.The maximum adsorption capacity of MWCNT/NH2-MIL-53（Fe）composites for tetracycline and chlortetracycline was 368.49 and 254.04mg g-1,respectively,which was 1.79 and 8.37 times that of straw biochar for antibiotics.After MWCNT was introduced into NH2-MIL-53（Fe）,the mesoporous ratio of MWCNT/NH2-MIL-53（Fe）composites was significantly increased,which was conducive to the generation of more active adsorption sites.In addition,the adsorption capacity of MWCNT/NH2-MIL-53（Fe）composites was significantly increased by the hydrogen bonding between the amino functional groups on the MWCNT/NH2-MIL-53（Fe）composites and the hydroxyl functional groups on tetracycline and chlortetracycline.In addition to fitting well with pseudo-second-order kinetic model and Langmuir model,adsorption experimental data were also fitted with intra-particle diffusion model and Temkin model,which further demonstrated that in-particle diffusion was not the only rate limiting step,and there were other interactions besides chemical adsorption.In addition,theπ-πbond interaction is considered to be the main reason for tetracycline and chlortetracycline adsorption.This study showed that MWCNT/NH2-MIL-53（Fe）composites had good adsorption and reusability in removing tetracycline and chlortetracycline from water.（chapter 4）In this study,Ni-MIL-53（Fe）material was prepared by solvothermal method based on MIL-53（Fe）,and used as the adsorbent to remove doxycycline antibiotics in water.The factors affecting doxycycline adsorption were evaluated by using the central combined design model（CCD）in response surface analysis（RSM）.PH,doxycycline concentration,temperature and ionic strength were optimized,and the predicted maximum adsorption capacity was compared with the actual maximum adsorption capacity.In addition,the reusability of Ni-MIL-53（Fe）material was analyzed.Response surface analysis results showed that the optimal adsorption conditions were as follows:doxycycline concentration of 100 mg L-1,temperature of 35°C,ionic strength of 5g L-1 and pH value of 7.The maximum theoretical adsorption capacity of 398.53 mg g-1,and the maximum actual adsorption capacity of 397.22 mg g-1,which was close to the theoretical value.The study of adsorption mechanism shows that the adsorption process is dominated by electrostatic interaction andπ-πbond interaction.Ni-MIL-53（Fe）material has good adsorption property and great potential in removing doxycycline from water.（chapter 5）In this study,MIL-53（Fe）was used as the base material to prepare magnetic carbon-αFe/Fe3C-910 derivatives by calcining under nitrogen atmosphere,and the removal behavior and mechanism of tetracycline antibiotics in actual water were studied.In addition,the reusability of magnetic carbon-αFe/Fe3C-910 derivatives was analyzed.In addition to conventional characterization methods such as scanning electron microscope（SEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,energy spectrometer（EDS）,automatic surface analyzer（BET）and thermogravimetric analysis（TGA）,the magnetic st rength of magnetic carbon-αFe/Fe3C-910 was analyzed by vibration sample magnetometer（VSM）.The magnetized saturation value and coercivity value of magnetic carbon-αFe/Fe3C-910 were 55.51 emu g-1 and 181.61 Oe respectively,indicating that the material has strong magnetism.Magnetic carbon-αFe/Fe3C-910 has a large specific surface area(171.72 m2 g-1),pore volume(0.31 cm3 g-1)and abundant active adsorption sites,and has good adsorption capacity for tetracycline in water(511.06 mg g-1).In addition,magnetic carbon-αFe/Fe3C-910 can remove tetracycline in aqueous solutions with lower concentrations(<5 mg L-1).The magnetic carbon-αFe/Fe3C-910 has great potential in practical applications due to its magnetism,good adsorption and reusability.（chapter 6）... |
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