Facile synthesis of highly reactive and stable Fe-doped g-C₃N₄ composites for peroxymonosulfate activation: A novel...

Ferrous ions (Fe²⁺) are environmentally friendly materials but show extremely inefficient persulfate activation. Polymeric graphitic carbon nitride (g-C₃N₄) has recently shown potential to activate persulfates, but the process requires intense light irradiation. To overcome these drawbacks, we designed an innovative heterogeneous iron catalyst by doping Fe into g-C₃N₄ (Fe-g-C₃N₄) and used it to activate peroxymonosulfate (PMS) for degradation of pollutant phenol. The catalysts synthesized were fully characterized with various techniques, such as X-ray diffraction, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. Fe was found to be coordinated with the framework of g-C₃N₄. Approximately 100% degradation of phenol was achieved with Fe-g-C₃N₄ after 20 min of reaction, whereas less than 5% degradation of phenol was achieved with Fe²⁺. Fe-g-C₃N₄-PMS had a wide effective pH range, and its reactivity was nearly independent of natural illumination. In contrast to the previously proposed radical mechanisms, quenching experiments revealed that nonradical oxidation contributed to the observed degradation. The OO bond in the activated PMS likely underwent heterolysis, producing high-valence iron species (Fe^IVO) as the primary active species. These findings have important implications for the development of a selective heterogeneous nonradical-oxidation process.