The role of iron-doped g-C₃N₄ heterogeneous catalysts in Fenton-like process investigated by experiment and theoretical simulation

The Fenton-like process provides a promising method to produce reactive radicals for the degradation of refractory organic pollutants in environmental remediation. In this study, the iron-doped g-C3N4 (CNF) coupled with H2O2 was applied to enhance the degradation of carbamazepine (CBZ). And the role of CNF was elucidated by experiment and density functional theory (DFT) calculations. The largest CBZ removal efficiency of 99.02% was achieved in acid condition (pH = 3) with the addition of 0.5 g/L 14% CNF and 50 mM H2O2. Thirteen intermediates were identified based on high performance liquid chromatography coupled with mass spectrometer (LCMS) and DFT calculations. The degradation products of CBZ were mainly protein-like materials with a low humification degree. During the degradation process, H2O2 was preferentially adsorbed on the active Fe-O site of CNF by hydrogen bonding, hence the promoted electron transfer from H2O2 to Fe(III) contributed to the generation of Fe(II). Certain deformation of H2O2 was observed that the O-O bond length increased to about 1.51 angstrom. As a result, large amounts of radical species (center dot OH) were generated by H2O2 decomposition, which was responsible for attacking the CBZ molecules and proceeding the degradation reaction.