Peroxymonosulfate oxidation via paralleled nonradical pathways over iron and nitrogen doped porous carbons

Hierarchically porous iron/nitrogen-doped carbons (Fe-N-PC) were developed for the oxidation of ibuprofen (IBP) with peroxymonosulfate (PMS). The incorporation of trace-level iron and nitrogen dopants promoted the catalytic performance remarkably, leading to 4.8, 16.4 and 22.9-fold enhancement over N-doped carbon (N-PC), porous carbon (PC), and Fe-doped carbon (Fe-PC), respectively. Fe(III) was anchored in nitrogen-coordinated pots (Fe-N_x) in the sp²-hybridized carbon network, and graphitic-N could synergistically boost the catalysis. Notably, methyl phenyl sulfoxide (PMSO) transformation, quenching tests, in situ electrochemical analysis and Raman spectroscopy verified high-valent iron-oxo species and direct electron transfer pathway accounted for pollutant oxidation. The relationship between the kinetic constants (lnk_obs) and the oxidation peak potential (E_op) of pollutants was established with good correlation, manifesting particular selectivity toward oxidizing electron-rich pollutants and great immunity to background inorganic ions and natural organic matters (NOMs) for real wastewater treatment. The deactivation mechanisms of Fe-N-PC were revealed via surface oxidation and dopant refabrication. This work delicates to deepen the understanding of the nonradical mechanisms and structure-oriented PMS activation by engineered carbonaceous materials.