Removal Of Levofloxacin From Water With Activation Of Peroxomonosulfate Based On Cobalt/Iron Nanocomposoite

In the 21st century,human beings are facing serious water pollution problems,and the direction of water pollution control has changed from"standard discharge"to"water quality regeneration"and"standard improvement".With the modernization drive,the rapid development of medicine,agriculture and industry has complicated water quality.Traditional processes are difficult to effectively remove trace refractory organic compounds such as endocrine disruptors,antibiotics and perfluorinated compounds.However,heterogeneous catalysis based on sulfate radical is a new treatment technology that attracts much attention in this field.This advanced oxidation technology can be used in the advanced treatment of sewage plants to meet the requirements of water quality improvement and solve the problem of trace organic residues in the water.The improvement of catalytic activity and reusability of catalysts and the activation mechanism of bisulfate are the research contents to be improved and broken through.In this study,levofloxacin（LEV）as a typical fluoroquinolone antibiotic was used as a model pollutant,and peroxymonsulfate（PMS）were activated by cobalt-iron composite catalysts in this oxidation process.And the strong oxidizing species produced were used to effectively remove refractory organic compounds.The work has been carried out in preparation optimization and characterization of catalysts,analysis of influencing factors and discussion of degradation mechanism.In order to evaluate the application of the process as an advanced wastewater treatment unit,this study investigated the applicability of the system in the competition environment of impurities in the effluent from the secondary sedimentation tank of a sewage plant.Firstly,the single-factor test method combined with the LEV degradation and cataltsy characterization were adopted to optimize the preparation conditions of 0.5 mol/L NaOH concentration and 600℃calcination temperature.Composite catalysts with different cobalt-iron molar ratios were synthesized for LEV removal in the oxidation process.The characterization results show that the components of Co-Fe（0.25:1）,Co-Fe（0.5:1）and Co-Fe（0.75:1）were Fe₂O₃·Co Fe₂O₄,Co Fe₂O₄,Co₃O₄·Co Fe₂O₄,respectively.LEV removal efficiency showed that Co-Fe（0.75:1）had the fastest removal rate in the process.The LEV removal rate with addition of 0.2 g/L catalyst and 0.3 mmol/L PMS could reach 98%after 20 min.Then,the affecting factors include reaction conditions and water quality in the DI water were analyzed.The process has a wide range of pH application（5-11）.High concentration of HCO₃^-和HPO₄^2-buffered the pH of the solution and promoted the removal of LEV.Humic acid showed inhibition of LEV removal due to its organic competition.The influence of Fe³⁺,Mn²⁺and Mg²⁺on LEV removal were obvious due to their hydrolysis and competitive adsorption.The cyclic test results shows that this process is in the presence of cobalt iron ion release and the quantitative value is within the specified range.And secondary calcination of the catalyst was beneficial to the recovery of the high-efficiency catalytic activity.It was confirmed by free radical quenching test that the process mainly achieved the removal of LEV through the radical path of SO₄^·-and the non-radical path of ¹O₂.LEV degradation mainly through defluorination,dealkylation and decarboxylation,and produced inorganic products such as F-,NO₃^-,CO₂,H₂O.Finally,the process can effectively remove LEV and reduce COD after 20 min of reaction by adding 0.1 g/L catalyst and 0.2 mmol/L PMS in the effluent of secondary sedimentation in sewage plant,thus achieving the improvement of secondary effluent quality.