Degradation Of Sulfonamide Antibiotics By Fe Single-atom Catalyst Activated Peroxymonosulfate

The treatment of growing environmental pollution with oxidizing substances generated by activated persulfates is a very promising strategy.Single Fe atom catalysts have shown great potential for activation of PMS to degrade organic pollutants.However,the identification of reaction pathways and active sites for iron-activated peroxymonosulfate(PMS)over a wide pH range remains unclear,and the development of excellent catalysts with sufficient activity and stability at different pH conditions remains a long-term goal for practical applications as well.To this end,we have synthesized nitrogen-doped porous carbon materials loaded with Fe single atom(FeSA-CN and FeSA-N-CNT)by cage encapsulation method and double anchoring method,and used them for the activation of PMS to degrade sulfasalazine(SSZ)pollutants.The following conclusions were obtained:(1)FeSA-CN and FeSA-N-CNT can efficiently activate PMS to degrade SSZ,and both of them can maintain high removal efficiency of SSZ in a wide pH range,and the materials are stable and both are reusable and renewable,with good environmental friendliness.(2)Hydroxyl radical(OH)、sulfate radical(SO4·-)and singlet oxygen(1O2)exist in the FeSA-CN/PMS system,and different reactive oxygen species(ROS)contribute differently to SSZ oxidation at different pH values.Fe-pyridine N4 is the best position for SSZ adsorption,and the adsorption efficiency of FeSA-CN material for SSZ is related to the content of pyridine N.1O2 is generated by adsorption of two PMS ions on the single atomic site of Fe and then by a two-step reaction.(3)·OH,SO4·-,1O2 and superoxide anion radical(O2-)exist in the FeSA-N-CNT/PMS system.·OH、SO4·-and other ROS contributed 56.3%,11.8%and 32.0%to the degradation of SSZ,respectively,among which ·OH and SO4·-had the priority to oxidize SSZ.Fe-pyridine N4 was the active site of PMS activation.Electrons transfer between Fe-pyridine N4 and C atoms adjacent to pyridine N.