Graphitic carbon nitride (g-C₃N₄) has proved to be a promising heterogeneous photocatalyst in the visible range. It can be used, among others, for the oxidative conversion of environmentally harmful nitrophenols occurring in wastewater. However, its photocatalytic activity needs to be enhanced, which can be achieved by modification with various dopants. In our work, copper-modified g-C₃N₄ was prepared by ultrasonic impregnation of the pristine g-C₃N₄ synthesized from thiourea. The morphology, microstructure, and optical properties of the photocatalysts were characterized by XRD, FT-IR, DRS, SEM, XPS, and TEM. DRS analysis indicated a slight change in both the CB and the VB energies of Cu/g-C₃N₄ compared to those of g-C₃N₄. The efficiency of the photocatalysts prepared was tested by the degradation of nitrophenols. Copper modification caused a sevenfold increase in the rate of 4-nitrophenol degradation in the presence of H₂O₂ at pH = 3. This dramatic enhancement can be attributed to the synergistic effect of copper and H₂O₂ in this photocatalytic system. A minor Fenton reaction role was also detected. The reusability of the Cu/g-C₃N₄ catalyst was demonstrated through five cycles. Copper-modified g-C₃N₄ with H₂O₂ proved to be applicable for efficient visible-light-driven photocatalytic oxidative degradation of nitrophenols.

Graphitic carbon nitride (g-C₃N₄) as a fascinating conjugated polymer has attracted considerable attention due to its outstanding electronic properties, high physicochemical stability, and unique structure. In this work, we reported the characterization of g-C₃N₄, which was simply synthesized by thermal polymerization of thiourea, the photocatalytic degradation kinetics, and the pathway of levofloxacin (LEV) using the prepared g-C₃N₄. The XRD and SEM results confirmed a crystalline graphite structure with a tri-s-triazine unit and stacked sheet-like layers of g-C₃N₄. The efficacy factor (EF) was compared to different photocatalytic processes to assess the LEV removal performance. g-C₃N₄ exhibits good stability as a photocatalyst during LEV photodegradation. Radical scavenger experiments revealed that in the oxidative degradation of LEV, ^•O₂^– and h⁺ played the determining roles. Moreover, based on the identification of intermediates using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the degradation pathway of LEV was proposed.