Photocatalytic degradation of pharmaceuticals by pore-structured graphitic carbon nitride with carbon vacancy in water: Identification of intermediate degradants and effects of active species

Abstract

Pharmaceuticals are increasingly used in daily life and have been massively discharged to the aquatic environment. The removal of pharmaceuticals from water by various nanomaterials including graphitic carbon nitride (g-C3N4) has received extensive attention. Herein, we synthesized a carbon-defective carbon nitride with pore structure through a simple thermal polymerization method for photodegradation of lidocaine, mepivacaine and ropivacaine (typical amide local anesthetics). The results showed that the degradation process conformed to the pseudo-first-order reaction kinetics, and the degradation rate constant of organic pollutants using CCN-600 (i.e., g-C3N4 synthesized at 600 °C) reached 5.05 × 10−2 min−1, about 2.5 times higher than that of the prototype g-C3N4 (2.09 × 10−2 min−1). The capture experiment of active species and the electron paramagnetic resonance (EPR) test demonstrated that superoxide radical (O2−) played a major role in the degradation process. Based on the possible photodegraded intermediate products identified, the degradation pathways were deduced. This study provides not only a new strategy for fabrication of pore-structured g-C3N4 with carbon vacancy, but also a reference method for the treatment of pharmaceuticals in water bodies.