Magnetic nitrogen-doped carbon nanotubes as activators of peroxymonosulfate and their application in non-radical degradation of sulfonamide antibiotics

Advanced oxidation processes based on peroxymonosulfate (PMS) are an efficient strategy to eliminate environmental micropollutants. Carbon nanotubes (CNTs) have been used as activators for PMS, but they still suffer from complex preparation processes and suboptimal catalytic performance. In this study, nitrogen-doped CNTs encapsulating cobalt nanoparticles (CoNCT) were prepared by a facile and economical calcination method using graphitic carbon nitride as a precursor. As expected, this novel CoNCT catalyst could rapidly activate PMS, and the CoNCT/PMS system could efficiently degrade eight types of sulfonamide antibiotics. It should be noted that singlet oxygen rather than the conventional sulfate and hydroxyl radicals were the predominant reactive species in the CoNCT/PMS system, which revealed a non-radical mechanism for the activation of PMS by CNTs. With the benefit of this mechanism, the CoNCT/PMS system maintained good oxidation performance over a wide pH range and exhibited strong resistance to anions, dissolved organic matter, and real water matrixes. This work not only contributes to the development of efficient carbon nanotubes as PMS activators, but also provides comprehensive insights into the non-radical mechanism involved in advanced oxidation processes for environmental decontamination.