Photocatalytic degradation of the antidepressant drug Paroxetine using TiO₂ P-25 under lab and pilot scales in aqueous substrates

Pharmaceuticals in water bodies are a significant threat to aquatic life and human health, often persisting due to incomplete degradation in conventional wastewater treatment plants (WWTPs). Heterogeneous photocatalysis is a promising method for efficiently treating wastewater (WW). TiO2 P-25, a well-known photocatalyst, has been widely used to remove persistent organic pollutants (POPs) from aquatic media, primarily on a laboratory scale. In this study, the photocatalytic removal of Paroxetine (PXT), an antidepressant drug, is investigated at the lab scale and pilot scale using a compound parabolic collector (CPC) reactor (85 L) working in batch recirculating mode and secondary treated hospital wastewater (HWW) as the substrate using different catalyst concentrations (200, 300, and 500 mg/L). The lab experiments achieved the fastest PXT degradation with 500 mg/L, while the pilot tests found 200 mg/L to be optimal. Thirteen transformation products (TPs) were identified using liquid chromatography-high-resolution mass spectrometry (LC-HR-MS-Orbitrap), and their ecotoxicity was assessed with ECOSAR software, indicating they were less toxic than PXT. The T.E.S.T. software showed most TPs were not mutagenic but displayed developmental toxicity. Toxicity assessments from the pilot scale using the Microtox bioassay demonstrated that toxicity was eliminated by the end of the photocatalytic treatment. In conclusion, the study provides an integrative approach to photocatalytic degradation of PXT, integrating lab-scale and pilot-scale experiments, pure water and real WW matrices, environmentally relevant concentrations, TPs’ identification along with toxicity assessment of both in-silico and in-vitro , which is not followed in most previous studies dealing with the photocatalytic degradation of pollutants.