ZnCo-MOF Derived Magnetic Cobalt-carbon Nanoclaster Composite For Efficient Activating Peroxymonosulfate To Degrade Levofloxacin

Levofloxacin（LEV）is widely used in medical industry because of its excellent bacteriostatic and bactericidal effects.While its high solubility in the environment and tendency to accumulation poses a potential risk to the water environment and humans,therefore it is urgent to find an effective treatment method to remove levofloxacin and its by-products from wastewater.Advanced oxidation techniques based on peroxynitrite activation can utilize sulfate radicals（SO₄^-·）and hydroxyl radicals（·OH）with high oxidation potential to oxidatively degrade antibiotics.Metal organic frameworks（MOFs）obtained by carbonization reduction of carbon material loaded metal catalysts are widely used for catalytic activation of persulfate to degrade biodegradable organic pollutants due to their excellent catalytic activity and good stability.In this study,a carbon material-loaded metal catalyst Zn₁Co₁-C-900,prepared by carbothermal reduction with ZnCo-MOF5 as the precursor,was firstly constructed for the efficient removal of levofloxacin（LEV）from wastewater.Nitrogen-doped Zn₁Co₁-C-900 was prepared by carbon thermal reduction with precursor ZnCo-MOF to improve the degradation efficiency of LEV,and the effect of nitrogen doping on the catalytic efficiency was further investigated.To solve the problem of low yield and small particle size of Zn₁Co₅-CN-900,it was prepared by loading Zn and cobalt with polyester waste to increase the particle size and cobalt loading,so that Zn₁Co₅/P₄-CN-900 could be better recovered and recycled.The main research contents and conclusions are as follows:（1）A simple bimetallic organic framework（ZnCo-MOF5）was prepared by one-step precipitation method and used as precursor to prepare MOFs derived porous carbon-supported Co⁰ nanoclusters（Zn₁Co₁-C-900）by a carbothermal reduction method.XRD,SEM,BET,XPS,Raman and other characterization methods were used to analyze Zn₁Co₁-C-900,revealing the influence of zinc doping,carbonization temperature and Zn-Co mole ratio on the physicochemical properties of Zn₁Co₁-C-900 catalyst.Zn₁Co₁-C-900 was applied to activate persulfate（PMS）to degrade organic pollutants in water,and the catalytic system Zn₁Co₁-C-900/PMS was constructed to degrade organic pollutants,and its activity was evaluated by LEV degradation efficiency.In the Zn₁Co₁-C-900/PMS system,the degradation efficiency and kinetic rate constant of LEV reached 87.87%and 0.189 min^-1 within 60 min respectively,which were much higher than that of Zn-C-900 and Co-C-900.The main active species in the system were identified as SO₄^-·and·OH by radical quenching experiments and EPR tests.Zn₁Co₅-CN-900 could be recycled five times with good stability.The intermediates were identified by liquid chromatography-mass spectrometry（LC-MS）analysis,and possible degradation pathways were suggested.（2）Based on the synthesized Zn₁Co₁-C-900,the effect of nitrogen doping on the metal-loaded catalysts of carbon materials was investigated,and a simple bimetallic imidazolium skeleton zeolite（ZnCo-MOF）was prepared by one-step precipitation method,and it was used as a precursor to prepare a porous carbon（CN）anchored Zn/Co atomic catalyst（Zn₁Co₅-CN-900）by carbothermal reduction precursor.XRD,SEM,BET,Raman,and XPS were used to characterize the Zn₁Co₅-CN-900.Nitrogen doped can simultaneously improve the adsorption capacity and catalytic activity of carbon materials for organic pollutants,and the Zn₁Co₅-CN-900 was used to activate peroxynitrite（PMS）to construct the Zn₁Co₅-CN-900/PMS catalytic system for the degradation of organic pollutants.In the Zn₁Co₅-CN-900/PMS system,the degradation efficiency and rate of LEV reached 98.3%and 0.228 min^-1within 60 min,respectively,which were higher than other activated systems.This was mainly due to the good dispersion of zero-valent cobalt nanofractions with nanopore structure.The degradation rate of levofloxacin by Zn₁Co₅-CN-900only decreased by 7.7%after five cycles,which has good stability.The intermediate products of levofloxacin degradation were analyzed by HPLC-MS,and possible degradation pathways were proposed.Therefore,a zero-valent cobalt nanoparticle anchored on CN was designed and Zn₁Co₅-CN-900/PMS system with good activity and reusability was constructed for levofloxacin degradation.（3）Zn₁Co₅/P₄-CN-900 composites were synthesized by one-step precipitation-carbonation reduction method using cobalt acetate,zinc acetate and polyester waste as raw materials to avoid the disadvantage of low yield and difficult to recycle in powder form.The Zn₁Co₅/P₄-CN-900/PMS system was constructed to analyze its degradation mechanism and degradation process of levofloxacin,and the stability of Zn₁Co₅/P₄-CN-900 was elucidated.