Fast degradation of rhodamine B by peroxymonosulfate activated with Fe–N carbon nanotubes

In this study, Fe–N co-doped carbon nanotubes (Fe–N-CNTs) were prepared and used to activate peroxymonosulfate (PMS) for advanced oxidation removal of Rhodamine B (RhB). The XRD, XPS, SEM and EDS results revealed that the Fe, N, O co-doped carbon nanotubes (Fe–N-CNTS) coated with FeO(OH) nanosheets were successfully synthesized by a simple pyrolyzing process. The large BET specific surface area (286.42 m²/g) and hybrid pore structure of micropores and mesopores (3–10 nm) of the Fe–N-CNTS ensured its good RhB degradation performance (98% in 30 min) by activatting PMS. The Fe–N-CNTS-1.5 had the best degradation performance, which could be attributed to the synergy effect between FeO(OH) nanosheets and Fe–N-CNTS. The ¹O₂, O₂•, •OH and SO₄^−• were formed during the PMS activating process and involved in the RhB degradation. The reaction constant of 0.5483 min⁻¹ could be obtained by adding 1.5 mM PMS, which is about 12 and 24 times of the reaction constant of PMS only (0.0458 min⁻¹) and FeN-CNTS only (0.0226 min⁻¹), respectively. This work provides new insight into the mechanism of PMS activation by carbon-based catalysts for the efficient degradation of RhB.