Heterogeneous Fenton oxidation of phenol photo-assisted with visible radiation in the presence of g-C₃N₄ catalysts modified with different iron phases

This work compared graphitic carbon nitride (g-C₃N₄) modified with different iron phases to maximize its catalytic response in the phenol degradation at circumneutral pH under visible irradiation (Xe lamps, 70 W) and H₂O₂. The semiconductor was modified with different iron phases either: (i) supported (Feⁿ⁺/g-C₃N₄, Fe₃O₄/g-C₃N₄ and α-Fe₂O₃/g-C₃N₄) or (ii) doped (Fe-g-C₃N₄). The materials were characterized by AAS, DRIFTS, DR-UV–Vis, N₂ adsorption, TGA, H₂-TPR, XPS, and XRD. Fe-g-C₃N₄ degraded 85 % of phenol (45 min), mineralized 62 % of DOC (180 min), leaching negligible iron (0.00131 mg Fe/L) at 25.0 ± 0.2 °C and pH 7.0. At pH 3.0, both phenol degradation (90 min) and mineralization (210 min) reached 100 %. The highly specific location of the metal within the lattice of the semiconductor substantially improved the use of the visible-light-photogenerated electron-hole pairs by the heterogeneous Fenton catalytic system in comparison to the metal oxides deposited on its surface.