Calcination temperature regulates non-radical pathways of peroxymonosulfate activation via carbon catalysts doped by iron and nitrogen

Abstract

Switching the reaction routes between radical pathways and non-radical ones in peroxymonosulfate (PMS) activation has attracted much interest, however, the regulation between non-radical pathways remains elusive. Herein, we reported the regulation of the dominant non-radical routes in PMS activation with carbon catalysts doped by iron and nitrogen (Fe-N/C) through varying the calcination temperatureof conductive polymer Fe-polyaniline complexes. High calcination temperatures ranging from 300 °C to 900 °C boosted the catalytic activity and surprisingly switched the non-radical activation routes from electron transfer to singlet oxygen (1O2) and high-valent iron-oxo species (HV–FeO). Pyrrolic N and CO formed at 300 °C accounted for the electron transfer process, while graphitic N, O–CO, and Fe–Nx formed over 700 °C were key catalytic sites responsible for the production of 1O2 and HV–FeO. Moreover, the catalyst calcinated at 900 °C (900@Fe-N/C-2) maximized bisphenol A removal by 96.4% and TOC removal by 83.0%. The optimal 900@Fe-N/C-2/PMS system could work efficiently over a wide pH range or coexisting water components. This study provided a facile strategy to regulate PMS non-radical pathways for the treatment of complicated wastewater.