Removal Of Cr(Ⅵ) And Norfloxacin From Water By Immoblied Iron-based MOF

With the development of industry,heavy metals and organic pollutants pose a great threat to human health and ecological balance,and have attracted much attention in recent years.So far,a lot of efforts have been made in the fields of adsorption,biodegradation,ion exchange,membrane filtration and photocatalytic degradation,among which,photocatalytic degradation is the more effective method because of its low cost,high efficiency,mild reaction conditions and no secondary pollution and has received wide attention.Conventional MOFs catalysts are in powder form,which limit their application in industrial water treatment due to their easy agglomeration,difficult separation and short service time.In this study,Fe-MOF（MIL-101（Fe）-NH₂）and supportsα-Al₂O₃were selected to synthesize a new metal-organic framework material membrane using secondary reaction inoculation method.Cr（Ⅵ）and norfloxacin were used as target targets to investigate their performance of photocatalytic reduction of hexavalent chromium and degradation of norfloxacin through experiments respectively.The effect of the materials in photocatalytic reduction of Cr（Ⅵ）in a continuous device containing a fixed bed reactor was investigated,and finally the reaction mechanism was investigated.The specific work of this thesis is as follows:1.The novel MOFs membrane material MIL-101（Fe）-NH₂@Al₂O₃（MA）was constructed by synthesizing MIL-101（Fe）-NH₂on alumina substrates using the secondary reaction seeding method.It was characterized by XRD,AFM,TEM,etc.Through the study of its catalytic properties,it was found that MA was good at photo-Fenton degradation of norfloxacin（NOR）under 80 min of visible light.Degradation efficiency were above 97%, compared with powder MIL-101（Fe）-NH₂material,the number of cycles of the membrane can reach 10 times.In this work,the effects of pH,foreign ions and H₂O₂ addition on the photo-Fenton degradation of NOR were explored.The prominent performance of·O₂^–、¹O₂and·OH radicals in the decomposition of antibiotic molecules was further demonstrated by active substance capture experiments,fluorescence emission spectroscopy tests and electron spin resonance tests.Three possible pathways for photo-Fenton NOR degradation were proposed based on HPLC/MS analysis and Fukui index.A toxicity assessment software tool（T.E.S.T）was used to evaluate the acute toxicity of NOR（fish）,bioaccumulation factors and its degradation intermediates.The combined results indicated that the MA/H₂O₂/vis system could degrade NOR to certain less toxic intermediates and even to certain inorganic molecules,such as carbon dioxide and water.2.The novel MOF membrane material MIL-101（Fe）-NH₂@Al₂O₃（MA）,assisted by oxalic acid（hole trap/reducing agent）,has excellent performance in photocatalytic reduction of Cr（Ⅵ）.Under white light irradiation,the efficiency of MA in reducing Cr（Ⅵ）was 100% within 8 min and could be recycled more than 20 times.The effects of different pH,initial concentration,oxalic acid addition,and real sunlight on the photocatalytic reduction of Cr（Ⅵ）were investigated,and MA had good Cr（Ⅵ）reduction performance over a wide initial pH range.The effect of co-existing inorganic ions on Cr（Ⅵ）reduction in simulated tanning wastewater was evaluated by a Box-Behnken surface response design,with the three variables influencing Cr（Ⅵ）reduction in the order B(SO₄^2-)>A（Oxa）>C（Cl^-）.The mechanism of Cr（Ⅵ）reduction was proposed by active matter capture experiments, fluorescence emission spectroscopy tests and electron spin resonance tests.e^-and CO₂^·- radicals can react with Cr（Ⅵ）to form Cr（III）,respectively.The prepared MA photocatalyst can overcome the difficulties and challenges of recycling conventional powder MOFs photocatalysts.3.Based on the excellent performance of MIL-101（Fe）-NH₂@Al₂O₃（MA）for the reduction of Cr（Ⅵ）,design a set of continuously operating devices using a fixed-bed reactor,and optimize the process parameters and reaction conditions of the devices.The reduction efficiency of Cr（Ⅵ）was maintained at 100%for 0-30 hours of continuous operation of the device,and for 30-45 hours,Cr（Ⅵ）can be reduced by more than 90%.Finally,for 45- 50 hours,the Cr（Ⅵ）reduction efficiency decreased to approximately 80%.In addition, the effects of simulated leather tanning wastewater,simulated seawater,lake water and tap water,as well as the stability and long-term activity of the MA photocatalyst and sunlight on its reduction of Cr（Ⅵ）were explored.