Adsorption and photocatalytic degradation kinetics of pharmaceuticals by TiO₂ nanowires during water treatment

The adsorption and photocatalytic degradation of 15 different pharmaceuticals in the presence or absence of UV was comparatively studied using titanium dioxide (TiO₂) anatase and rutile nanowires as well as commercially available TiO₂ (P25) nanoparticles. Both anatase and rutile nanowires were grown under environmentally benign hydrothermal conditions. The kinetic adsorption studies demonstrate adsorption is usually complete within 20-40 min. The nanomaterials evaluated differed in photocatalytic efficiency by compound, with the UV-exposed anatase-phased nanowires being more effective at degrading venlafaxin, atorvastatin, ibuprofen, naproxen, gemfibrozil, lincomycin, norfluoxetine, diclofenac, and trimethoprim, while the rutile-phased nanowires were more effective for fluoxetine and norfluoxetine. The sole exposure to 265 nm UV leads to effectively decay sulfamethoxazole (SFX) and atrazine. Intermediate analysis unveils a higher mineralization of SFX is obtained with TiO₂ photocalytic degradation compared to the photolysis with a UVC at 254 nm. These initial studies provide mechanistic insight into the effectiveness of TiO₂ nanowires and nanoparticles for treatment of surface and drinking waters containing trace pharmaceutical residues.