Metal-Organic Framework-Derived Iron-Cobalt/Nitrogen-Doped Porous Carbon As Heterogeneous Electro-Fenton Catalyst For The Degradation Of Tetracycline

Electro-Fenton process has gained considerable attention in the removal of antibiotics.However,it exhibited some drawbacks,such as slow regeneration of Fenton catalytic sites,acidic condition and low H₂O₂ yield.These shortcomings can be solved through appropriate design and optimization of heterogeneous electro-Fenton catalysts.Metal-organic framework（MOF）has the superior features like diverse structure,abundant functional group and large specific surface area.Moreover,MOF derivatives have the advantage of high water stability and electrical conductivity.In this study,Fe/Co nanoparticles embedded N-doped porous carbon composites（Fe₂Co₁/NPC）were prepared by using Co/NH₂-MIL-88（Fe）as precursor.The morphology,composition and electrochemical properties of composites were explored through various characterization technologies.Besides,the composite was utilized as heterogeneous electro-Fenton catalyst for the removal of tetracycline（TC）.The parameter of material preparation,operation parameter,stability,degradation mechanisms and pathways were explored.The main results are as follows:（1）The Fe₂Co₁/NPC material remained the rod-like morphology of pristine MOFs and exhibited a typical core-shell structure.The content of Fe⁰ in the material increased significantly after N and Co doping,and the content of Fe⁰ and Fe₃O₄ was highest when Fe:Co=2:1.After carbonization,the specific surface area of the material increased significantly.The resistance of the material decreased after N doping,which was beneficial to the electron transfer between porous carbon and iron oxide.（2）The incorporation of N and Co could both promote the degradation of TC,and the improvement efficiency was 16.3%and 2 6.2%,respectively.The composites exhibited the best degradation performance when Fe:Co=2:1.The study of operation parameter indicated that acidic condition was beneficial to the heterogeneous electro-Fenton performance,and the degradation efficienc y of TC could obtain 91%under neutral condition.Meanwhile,the optimal current and catalytic dosage was 100m A and 0.3 g L^-1,respectively.Chloride ions could enhance the degradation of TC,while bicarbonate ions would inhibit the oxidation of TC.（3）The leaching concentration of Fe and Co was 0.803 mg L^-1and 0.493 mg L^-1respectively.After four cycling tests,the removal efficiency of TC could still reach85%.These results showed that the system exhibited excellent stability.In addition,Fe₂Co₁/NPC-heterogeneous electro-Fenton system achieved high removal efficiency in different water bodies and different antibiotic wastewaters,indicating the material ha d good adaptability.（4）Radical quenching tests revealed that·OH played a dominant role in the system.The mechanisms mainly included the reduction of dissolved oxygen to produce H₂O₂,the activation of H₂O₂ by Fe^Ⅱ/Co^Ⅱ in the catalyst to generate OH,and the synergistic effect of N-doped porous carbon and bimetals to promote the reduction and regeneration of Fenton catalytic sites.The detection of intermediate products showed that the degradation process of TC mainly included group detachment（methyl group,amino group,carboxyl group,aldehyde group,etc.）,dehydration and ring opening,and finally mineralized into CO₂ and H₂O.