Removal of clozapine from polluted waters via C₃N₄ based materials

New photocatalysts with a g-C₃N₄-ZnO heterojunction were prepared following different synthetic routes, fully characterized, and evaluated for the abatement of the antipsychotic drug clozapine. Experiments were performed with clozapine standard and clozapine based commercial tablet solutions in a sun simulator and the evaluation of clozapine removal was assessed in different aqueous media: Milli-Q and natural water (Po River) to evaluate the role of natural occurring components on the drug removal efficiency. The photocatalyst prepared via hydrothermal method (CA_1) exhibited the highest efficiency, allowing to achieve the complete abatement of clozapine within 30 min, in Milli-Q water. Its photocatalytic performance decreased in river water, where the total drug degradation was obtained after1h, and is notably inhibited on Leponex tablets (80% removal after 1 h of irradiation). Clozapine degradation proceeds through the formation of nineteen (19) transformation products, all less hazardous that the parent compound, as proved by the acute and chronic toxicity valued by ECOSAR. Mechanistic studies evidenced that OH⦁ radicals are the key reactive species involved in the pollutant removal, while other species such as superoxide radical anion (O₂•⁻) and especially singlet oxygen (O₂¹) played a marginal role in the degradation process. [Display omitted] •New photocatalysts characterized by a g-C₃N₄-ZnO heterojunction were prepared.•DEP 3:1 and CA_1 were the most efficient photocatalysts (t1/2≈26 and 29 min in tablets).•OH˙ are the key reactive species involved.•Nineteen transformation products were formed during the drug transformation.