Effet of chemical compounds in soil solution to the photocatalytic activity of TiO₂ NPs.

In the present work, copper nanoparticles were deposited onto the surface of two different commercial titanias (Evonik Aeroxide P25 and Aldrich anatase). During the synthesis, the concentration of copper was systematically varied (0.5%, 1.0%, 1.5%, 5.0%, and 10 wt.%) to optimize the composite-composition. The photocatalytic activity was evaluated under UV-light, using methyl orange and Rhodamine B as model and ketoprofen as real pollutant. For the hydrogen production capacity, oxalic acid was used as the sacrificial agent. The morpho-structural properties were investigated by using XRD (X-ray diffraction), TEM (Transmission Electron Microscopy) DRS (Diffuse Reflectance Spectroscopy), XPS (X-ray Photoelectron Spectroscopy), and SEM-EDX methods (Scanning Electron Microscopy-Energy Dispersive X-ray Analysis). Increasing the copper concentration enhanced the photocatalytic activity for methyl orange degradation in the case of Aldrich anatase-based composites. When the P25-based composites were considered, there was no correlation between the Cu concentration and the activity; but, independently of the base photocatalyst, the composites containing 10% Cu were the best performing materials. Contrarily, for the ketoprofen degradation, increasing the copper concentration deteriorated the photoactivity. For both Aldrich anatase and P25, the best photocatalytic activity was shown by the composites containing 0.5% Cu. For the degradation of Rhodamine B solution, 1.5% of copper nanoparticles was the most suitable. When the hydrogen production capacity was evaluated, the P25-based composites showed higher performance (produced more hydrogen) than the Aldrich anatase-based ones. It was found that Cu was present in four different forms, including belloite (Cu(OH)Cl), metallic Cu, and presumably amorphous Cu(I)- and Cu(II)-based compounds, which were easily convertible among themselves during the photocatalytic processes.