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.