When TiO2 meets pharmaceuticals: Photocatalytic degradation and environmental safety unveiled.

Building on our previous work on electrochemically synthesized anatase TiO2 nanoparticles (NPs), this study evaluates their environmental relevance by linking pharmaceutical photocatalytic degradation with transformation product identification and toxicity-oriented assessment. The incomplete removal of pharmaceuticals in wastewater treatment plants raises concerns about both parent compounds and transformation products formed during advanced treatments. Here, the synthesized TiO2 NPs were applied to the photocatalytic degradation of ibuprofen (IBU) and paracetamol (PCT) under ultraviolet A (UVA) irradiation. The TiO2 NPs showed higher degradation efficiency than commercial P25, with Kobs of 10.82 × 10-3 min-1 for IBU and 10.75 × 10-3 min-1 for PCT, and approximately 95% removal for both pollutants after 4 h of UVA irradiation. Liquid chromatography tandem mass spectrometry (LC-MS/MS) identified 8 transformation products for IBU and 9 for PCT, suggesting degradation pathways involving hydroxylation, decarboxylation, bond cleavage, and formation of smaller oxygenated products. In-vitro assays were performed using A549 lung cells and HepG2 liver cells. In A549 cells, TiO2 NPs caused no significant decrease in dehydrogenase activity at 1-100 µg/mL after 24 and 48 h. In HepG2 cells, TiO2 NPs showed lower cytotoxicity than P25, with viability remaining at approximately 68% after 48 h at 250 µg/mL, compared with about 60% for P25. IBU and PCT solutions before and after 4 h of photocatalytic treatment maintained HepG2 viability above 90%. The toxicity-oriented assessment, supplemented by Ecological Structure Activity Relationships (ECOSAR) software predictions, suggested that further transformation could reduce predicted ecological concern.