Photocatalytic degradation and transformation of pharmaceuticals using exfoliated metal-free g-C3N4.

Pharmaceuticals are micropollutants of global concern that contribute to environmental contamination alongside other anthropogenic and natural chemical compounds. This study addresses the photocatalytic degradation of model pharmaceutical compounds ofloxacin, diclofenac, and caffeine using bulk and thermally exfoliated graphitic carbon nitride (g-C3N4). Bulk g-C3N4 was synthesised from dicyandiamide at 550 °C and exfoliated at 500 °C for 1-3h in ambient atmosphere. The structural, textural, and electronic properties of the prepared materials were evaluated. Graphitic carbon nitride exfoliated for 2h provided the best photocatalytic degradation efficiencies (> 95 %) for both ofloxacin and diclofenac, and approximately 80 % for caffeine, determined for 120 min under irradiation at 420 nm. The pharmaceuticals were degraded, and their intermediate degradation products were investigated using liquid chromatography combined with high-resolution tandem mass spectrometry. The successful identification of the main degradation products allowed us to propose transformation pathways for the studied pharmaceuticals.