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

Abstract

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-Nx) 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 (lnkobs) and the oxidation peak potential (Eop) 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.