| Electro-Fenton?EF?process is a kind of efficient and environmentally friendly electrochemical advanced oxidation processes?EAOPs?,which the H2O2 in-situ produced by oxygen reduction reaction?ORR?was decomposed to·OH.However,the narrow p H range?2.8?3.5?and the generation of large iron sludge limit the wide application of homogeneous EF?homo-EF?.Thus,the heterogeneous EF?hetero-EF?has attracted extensive attention which might overcome the shortage of homo-EF widening the p H range.And the heterogeneous catalysts might directly affect the feasibility and efficiency of the hetero-EF process,thus,it's crucial to develop catalysts with high catalytic activity and stability.In this study,Mn/Fe@porous carbon?Mn/Fe@PC?was successfully fabricated through a simple calcination of Mn-doped MIL-53?Fe?precursor.The morphology,composition and electrochemical catalyst activity were investigated.The design of the heterogeneous catalyst in the study might be a new idea for the development of efficient heterogeneous-EF catalyst.In addition,the Mn/Fe@PC was also applied for cathode modification for triclosan?TCS?degradation in hetero-EF process to explore the mechanism,pathways and toxicity,in order to provide the theoretical basis for the removal of persistent organic pollutant.The main research results were as follows:?1?Mn/Fe@PC remained octahedron morphology,and the composite of the Mn/Fe@PC was mainly the porous carbon doped with metal nanoparticles.Mn doping decreased the size of the particles and increased the surface area to 351.0 m2 g-1.The characteristic peaks of Fe2p3/2 and Fe 2p1/2 migrated to low binding energy indicating the electron interaction between Fe and Mn.?2?The electrochemical activity area?EASA?of Mn/Fe@PC is 0.11 cm2,which is 1.97times and 4.17 times of Fe@PC and Mn@PC,respectively,comfirming the enhancement of the electron transfer with Mn doping.The ORR process on the the mixture of CB and Mn/Fe@PC was dominated by 2e-pathway with electron transfer number and production of H2O2 of 2.5?3.0 and 60%?70%,respectively.In addition,the reduction potential of Fe,Mn was lower which was beneficial for the generation of Fe?and Mn?.?3?In the hetero-EF process,TCS degradation with the Mn/Fe@PC modified cathode?Mn/Fe@PC-CP?was followed the first order reaction kinetics.The TCS removal efficiency and minerazation rate achieved 99%in 120 min and 56.9%in 240 min,respectively.The metal leaching and recycle experiments confirmed that the great stability of the Mn/Fe@PC-CP cathode.?4?The results of the radical quenching experiments and electron paramagnetic resonance?EPR?verified the main role of·OH.The in-situ generated H2O2 on the Mn/Fe@PC-CP cathode was decomposed to·OH by the activation of?Fe?/?Mn?/?.The direct reduction of Fe?/Mn?/?on the cathode and the electron transfer between?Fe and?Mn achieved the regeneration of?Fe?/?Mn?/?enhancing the utilization of H2O2 and TCS degradation.?5?The main pathways of TCS degradation in the system included hydroxylation and ether bond breaking and further mineralized.The toxicity analysis showed that the toxicity of the intermediates decreased with TCS degradation in the hetero-EF process. |
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