Transformation to nonradical pathway for the activation of peroxydisulfate after doping S into Fe3C-encapsulated N/S-codoped carbon nanotubes

Abstract

To understand the roles of S-doping in materials for the transformation of nonradical pathway in peroxydisulfate (PDS), magnetic nitrogen-sulfur-codoped carbon nanotubes with encapsulated Fe3C nanoparticles (Fe3C@NSCNTs) were synthesized to activate PDS for the degradation of bisphenol A (BPA). Fe3C@NSCNTs activated PDS through nonradical pathway based on electron transfer complexes with high BPA degradation efficiency (kobs = 0.202 min−1), which was ascribed to the doping of S. Notably, the encapsulated Fe3C played an important role in the Fe3C@NSCNTs for PDS activation but did not act as the directly active sites for PDS activation owing to the encapsulation. The synergistic effect of N and S provided a large contribution to the improvement on catalytic performance, and the S doping could transform the activation pathway of PDS to the nonradical pathway. The electron transfer complexes showed high anti-interference capacity of various pH, inorganic anions, NOM and different water bodies. Besides, it could degrade BPA even without additional PDS after an initial exposure to PDS. This study provides a renewable catalytic system for the removal of organic contaminants through nonradical pathways and new insight in effect of the S doping.