Co-Doping Graphitic Carbon Nitride with Fe Atoms and Oxygen-Containing Functional Groups for the Efficient Photo-Fenton Degradation of Sulfamethoxazole

Abstract

The treatment of antibiotic contaminants using photo-Fenton process presents a promising solution. In this study, graphite carbon nitride (CN) has been co-doped with Fe atoms and oxygen-containing functional groups (Fe/OA-CN) applying a one-pot calcination synthesis, and used to promote the degradation of sulfamethoxazole (SMX). Sample characterization has established an atomic dispersion of Fe in the CN framework. Meanwhile, oxygen functional groups were successfully introduced into CN in order to modulate the energy band structure and enhance the visible light response range. The co-doping of CN with Fe and O significantly improved the visible light absorption capacity and effectively suppressed the recombination of photogenerated electron-holes. Different influencing parameters, such as catalyst dosing, hydrogen peroxide dosing, SMX concentration, and water matrices, were considered and optimized to enhance the degradation and mineralization efficiency. At a concentration of 50 mmol/L of H2O2, 99% SMX (10 ppm) was removed by Fe/OA-CN (0.5 g/L) within 90 min. Singlet oxygen plays a major role in the degradation process and synergizes with hydroxyl radicals, oxygen anions, and holes to enhance the degradation efficiency of SMX. The present study provides a convenient and economical method for the synthesis of photo-Fenton catalysts modified by the co-doping of atomic Fe species and oxygen functional groups.

Keywords: sulfamethoxazole, Photo-Fenton, Single atom catalyst, graphite carbon nitride, Degradation mechanism