Iron anchored carbon–nitrogen catalyst for enhanced activation performance of peroxymonosulfate: Synergy of 1O2 and high-valent iron

Herein, Iron anchored in carbon–nitrogen nanosheets (Fe-CNx) catalysts were synthesized successfully through one-step in situ pyrolysis for activating peroxymonosulfate (PMS) to degrade sulfachloropyridazine (SCP). Fe-CN800/PMS could realized the complete removal SCP in 20 min (kobs = 0.644 min−1). Its reaction rates were 214.7 times higher than that in PMS system. Additionally, Fe-CN800 could effectively activate PMS in a wide range of pH (3–10.6). The relationship between the content of Fe-CNx functional groups and the catalytic performance indicated that C = O and Fe-N4 were the main active sites. The structural–functional association between active sites and reactive oxygen species (ROS) was revealed by regression analysis and Density Functional Theory calculations, indicating that C = O stimulated 1O2 production, while HV-Fe was derived from C = O and Fe-N4. Moreover, the PMS activation was enhanced via electron transfer between Fe(II) and Fe(III). Based on LC-MS and Fukui index, the action of ROS during SCP decomposition was analyzed, and proposed three probable pathways for SCP degradation. The transformation pattern of the structure and toxicity of the intermediates was revealed via T.E.S.T. analysis, and plant growth experiments showed that the effect of the treated SCP solution on Brassica napus significantly decreased. Finally, Fe-CN800 exhibited excellent stability, with SCP removal remaining above 95 % in five cycles and Fe leaching concentrations lower than ones which have been reported catalysts. This work provided new insights for the precise design of more efficient PMS catalysts. It will provide a fundamental basis for the practical application in wastewater treatment based on PMS-AOPs.