Construction of novel in-situ photo-Fenton system based on modified g-C3N4 composite photocatalyst

In this study, a reduced g-C3N4/PDI/Fe (R-gCPF) photocatalyst was synthesized by loading Fe ion onto a reduced g-C3N4/PDI (R-gCP), which was obtained by reducing g-C3N4/PDI with NaBH4. The synthesized R-gCPF photocatalyst was used to construct a novel in-situ photo-Fenton system under visible light for pollutants removal. The R-gCPF(2) (0.7% mass ratio of Fe/R-gCP) exhibited the optimal degradation efficiency toward benzoic acid (BA) and the photocatalytic degradation was much better than that of the unmodified g-C3N4/PDI (gCP). The X-ray photoelectron spectroscopy (XPS) characterization indicated that Fe was successfully loaded and bounded to the R-gCP material in the form of Fe2O3. The quenching experiments and the electron paramagnetic resonance (EPR) spectroscopic analysis revealed that the photo-Fenton system was built up, and water was oxidized to (OH)-O-center dot in the system. Further, the Mott-Schottky and UV-vis diffuse reflectance spectrometry (UV-vis DRS) measurements confirmed the ability of valence band on R-gCPF to oxidize water. Photoluminescence spectral (PL) analysis indicated that loaded Fe could promote the separation of photogenerated electrons and holes, and consequently improved the photocatalytic efficiency of materials. The effect of initial pH, different ions and dissolved organic matter (DOM) on BA degradation was also studied. The stability of the photocatalyst was confirmed by recycle and the leaching experiments.