Strongly coupled Fe/N co-doped graphitic carbon nanosheets/carbon nanotubes for rapid degradation of organic pollutants via peroxymonosulfate activation: Performance, mechanism and degradation pathways

Exploration of magnetic carbon-based catalysts with high catalytic activity and recyclability is essential for peroxymonosulfate (PMS) activation. A feasible method for the synthesis of Fe/N co-doped graphitic carbon nanosheets/carbon nanotubes (Fe/[email protected]) using a one-step pyrolysis procedure was proposed in this paper. The Fe/[email protected] possessed an interconnected carbon framework composed of GCNS and CNTs. The carbon framework could not only improve the mass transfer efficiency and mineralization capability of Fe/[email protected], but it could also protect the Fe nanoparticles against metal leaching. The as-obtained Fe/[email protected] demonstrated excellent performance for PMS activation to degrade organic pollutants. 100% of 50 mg/L rhodamine B (RhB) was rapidly degraded in 5 min when PMS (0.5 mM) and 50 mg/L Fe/[email protected] were added. Meanwhile, the Fe/[email protected]/PMS system possessed a broad efficient pH range (3.0–9.0), good anti-interference capacity (anions and HA), and low iron leaching concentration (138 µg/L). Fe/[email protected] could be magnetically separated from the suspension very easily because of its good saturation magnetization (11.25 emu/g). In addition, quenching experiments, electron spin resonance (ESR) measurements, and electrochemical assessments demonstrated that radical (.OH and SO4⋅−) and non-radical (1O2 and electron transfer) processes cooperated to contribute to the rapid RhB degradation. XPS analysis revealed that the primary catalytic active sites of Fe/[email protected] were pyridinic N, C=O groups, and Fe/Fe3C species. LC-MS analyses were used to propose possible RhB degradation pathways. This study provided an intrinsic mechanism of PMS activation by magnetic carbon-based catalysts for the removal of organic pollutants in water treatment.