The utilization of Fe-doped g-C3N4 in a heterogeneous photo-Fenton-like catalytic system: the effect of different parameters and a system mechanism investigation

Abstract

In this study, a series of Fe-doped g-C₃N₄ (Fe–C₃N₄) samples was synthesized and characterized via X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflection spectroscopy (UV-vis DRS), and photoluminescence (PL) spectroscopy. The photocatalytic activity of the synthesized Fe–C₃N₄ was investigated toward methylene blue (MB) degradation with hydrogen peroxide (H₂O₂) assistance. The results showed that the Fe–C₃N₄ heterogeneous photo-Fenton-like system showed excellent catalytic performance when the pH value was varied from 3.0 to 9.0. Evaluating the effects of various inorganic anions in the Fe–C₃N₄ heterogeneous photo-Fenton-like system, HCO₃⁻ showed a dual effect on MB degradation, and Cl⁻ and NO₃⁻ showed an inhibitory effect on MB degradation. Evaluating the effects of inorganic cations, Al³⁺, Mg²⁺, and Ca²⁺ strongly inhibited MB degradation. Recycling experiments demonstrated that Fe–C₃N₄ possesses good reusability and stability. Quenching experiments were carried out, and it was found that hydroxyl radicals (·OH) were the primary active species in the system. Besides, nine intermediates were identified via LC/MS, and a possible MB degradation pathway in the system was proposed. This study could promote the application of this Fe–C₃N₄ heterogeneous photo-Fenton-like system in realistic dye wastewater.