Photocatalytic Degradation of Selected Pharmaceuticals Using g-C₃N₄ and TiO₂ Nanomaterials

Exfoliated graphitic carbon nitride (g-C₃N₄) and two commercially available nanomaterials from titanium dioxide (P25 and CG300) were tested for the photocatalytic degradation of paracetamol (PAR), ibuprofen (IBU), and diclofenac (DIC). Prior to photocatalytic experiments, the nanomaterials were characterized by common methods, such as X-ray diffraction (XRD), UV-VIS diffuse reflectance spectroscopy (DRS), Fourier transformed infrared spectroscopy in attenuated total reflection mode (FTIR-ATR), transmission electron microscopy (TEM), physisorption of nitrogen, and dynamic vapor adsorption (DVS) of water. The sizes and specific surface area (SSA) of the TiO₂ nanoparticles were 6 nm and 300 m²·g^-1 for CG300 and 21 nm and 50 m²·g^-1 for P25. The SSA of g-C₃N₄ was 140 m²·g^-1. All photocatalytic experiments were performed under UV (368 nm), as well as VIS (446 nm) irradiation. TiO₂ P25 was the most active photocatalyst under UV irradiation and g-C₃N₄ was the most active one under VIS irradiation. Photodegradation yields were evaluated by means of high performance liquid chromatography (HPLC) and reaction intermediates were identified using gas chromatography with mass detection (GC-MS). Paracetamol and ibuprofen were totally removed but the intermediates of diclofenac were observed even after 6 h of irradiation. Some intermediates, such as carbazole-1-acetic acid, 2,6-dichloraniline, and hydroxylated derivates of diclofenac were identified. This study showed that g-C₃N₄ is a promising photocatalyst for the degradation of pharmaceuticals in an aqueous environment, under visible light.