Synthesis Of Immobilized MOFs Derivatives And Their Persulfate Activation Performance Toward Antibiotics Degradation

The contamination of water resources caused by antibiotics has attracted widespread attention.Among them,tetracyclines（TCs）are a typical broad-spectrum class of antibiotics and are one of the main antibiotics used in human disease treatment,animal disease control and agricultural feed additives.TCs mainly include tetracycline（TTC）,oxytetracycline（OTC）and chlortetracycline（CTC）,etc.,which are poorly absorbed and metabolized in humans and animals.Most of the TCs widely detected in water bodies such as surface water and groundwater are released into the environment through feces or urine.However,as an emerging pollutant,TCs are difficult to be biodegraded and are difficult to be removed by traditional water treatment processes.Persulfate-based advanced oxidation processes（PS-AOPs）can generate a large number of reactive oxygen species（ROSs）,such as hydroxyl radicals（·OH）,sulfate radicals（SO4-·）,superoxide radicals（·O2-）and non-radicals,etc.PS-AOPs are widely used for the removal of antibiotic pollutants because of their high degradation efficiency,fast reaction rate and environmental friendliness.However,this process is suffered from difficulty recycling the catalyst,being influenced by environmental factors,difficulty achieving continuous degradation and low removal rate of total organic carbon（TOC）.In this study,immobilized metal-organic backbone materials（MOFs）were used as precursors for the preparation of MOFs-derived immobilized catalysts for the removal of TCs by PS-AOPs process,and the efficiency of the reaction process was enhanced through the modulation of catalyst morphology and process coupling.Fe₃O₄ and immobilized N-C/Co catalysts were used as catalysts to investigate their performance in activation of persulfate degradation of TCs and to investigate the catalytic reaction mechanism.The continuous degradation of TCs was achieved in the process.The main findings and results of this thesis are as follows.（1）To improve the stability and recyclability of the catalyst,a novel immobilized M-Fe₃O₄-T@PBS catalyst was successfully prepared by immobilizing MIL-88A（Fe）on a commercial porous block substrate（PBS）using a room temperature stirring method and a one-step pyrolysis method at different temperatures（M and T represent magnetite and calcination temperature）.The peroxodisulfide（PDS）was activated under the irradiation of white light to achieve the efficient degradation of TTC.The results showed that the system could degrade TTC at an initial concentration of 10 mg L^-1 with an efficiency of 97.5%in 40 min,and the effects of PDS dosage,p H and coexisting ions on the degradation effect were investigated.It was demonstrated that the TTC removal efficiency could also reach 92.8%under real sunlight,and more importantly,the loss of catalyst during use was avoided due to immobilization,where M-Fe₃O₄-T@PBS possessed the simple recyclability and excellent reusability with high degradation performance even after 30 consecutive cycles.The possible degradation mechanism was investigated by different methods such as active substance capture experiments,electron spin resonance（ESR）tests to electrochemical analysis.In addition,the possible degradation pathways of TTC were analyzed based on the liquid chromatography-mass spectrometry（LC-MS）technique and the toxicity of the intermediates was reduced based on the quantitative constitutive relationship（QSAR）assessment.（2）To reduce the influence of environmental factors and further improve the degradation efficiency.ZIF-67 was immobilized on porous spherical substrates（PSS）,and ZIF-67-derived N-C/Co@PSS immobilization catalysts were prepared by pyrolysis.The performance of its activated peroxymonosulfate（PMS）was investigated for the simultaneous degradation of mixed tetracycline antibiotics（TCs,TTC,OTC,CTC）.The experimental results showed that ca.100%of TCs(initial concentration of 10 mg L^-1)could be achieved within 10 min.The effects of PMS dosage,p H,inorganic anions and actual water matrixes on the degradation effect and the recyclability of the materials were systematically investigated.Among them,N-C/Co@PSS not only has simple recyclability and excellent reusability,but also has high degradation performance after 30 consecutive cycles,and can effectively reduce the influence of environmental factors as well as possessed high catalytic degradation efficiency in both inorganic anions and actual water quality.The non-radical-based degradation mechanism was determined by active substance capture experiments,electrochemical analysis and ESR tests.Finally,the degradation pathways of pollutants and the toxicity of their intermediates were analyzed based on LC-MS analysis and quantitative constitutive relationship（QSAR）.（3）In order to achieve continuous flow degradation and improve TOC removal rate,a continuous flow degradation device based on N-C/Co@PSS immobilized catalyst was fabricated self-made to achieve efficient and dynamic degradation of TCs.After 200 h of continuous operation,efficient removal of TCs could still be achieved,which realized the separation-free catalyst and efficient dynamic degradation of TCs.The degradation effects of different TCs concentrations and in actual water bodies were investigated,and the subsequent coupling of ozone oxidation and UV/PDS processes achieved continuous degradation of TCs as well as efficient mineralization,which maximized the utilization efficiency of the catalyst and broadened the application of immobilized catalysts in PS-AOPs.