Iron active sites encapsulated in N-doped graphite for efficiently selective degradation of emerging contaminants via peroxymonosulfate (PMS) activation: Inherent roles of adsorption and electron-transfer dominated nonradical mechanisms

In this work, Fe-based graphite catalyst (Fe-0.6@N-GC) was successfully synthesized to degrade sulfisoxazole (SIZ) via peroxymonosulfate (PMS) activation. Fe-0.6@N-GC has large specific surface area and abundant pyridinic N sites, leading to superior SIZ adsorption. Complete degradation of SIZ (5 mg/L) can be achieved within 20 min in the Fe-0.6@N-GC/PMS system. Electrochemical analysis, electron paramagnetic resonance, scavenging and probe experiments illustrated that SIZ can be efficiently degraded via mediated electron transfer pathway from SIZ to PMS, as well as the partial contribution of singlet oxygen (O-1(2)). Meanwhile, stable encapsulation of scattered Fe sites on N-doped porous carbon greatly reduced the iron leaching (<= 0.023 mg/L). High selectivity for different pollutants degradation and tolerance of coexisting ions were performed which is beneficial to practical application. Finally, the possible degradation pathways were also proposed by analyzing intermediates. Overall, this study provides a new understanding of nonradical pathways in organic pollutants oxidation by catalysis of iron-based catalysts.