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 K_obs 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.