The effect of cobalt doping on the efficiency of semiconductor oxides in the photocatalytic water remediation

The effect of cobalt doping on semiconductors materials synthesized via solution and hydrothermal methods was investigated by testing its photocatalytic efficiency on pollutants abatement. X Ray Diffraction technique was used to evaluate samples crystallographic phases allowing to identify different species due to the introduction of the dopants. Diffuse Reflectance UV-vis Spectroscopy was employed to determine the bandgap as well as the absorption corresponding to d-d transitions for cobalt doped systems. Finally, Electron Paramagnetic Resonance Spectroscopy was adopted to perform a pre-screening of the photoactivity of the prepared samples. The Co-doped TiO2 and ZnO materials photoactivity was assessed on phenol degradation, selected as pollutant probe, under UVA irradiation. Doping TiO2 with cobalt in low amounts (0.25% and 0.5%) prepared by hydrothermal method leads to an enhancement on phenol degradation. Also, the presence of Co-doped ZnO obtained by hydrothermal process if prepared with defined cobalt amount (0.5 or 1%) promote an increasing on phenol abatement. Ketoprofen was used to evaluate the doping effect, being the Co-doped ZnO material more efficient on ketoprofen mineralization comparing with bare material. The ketoprofen and its transformation products were easily abated and, in wastewater, they were completely eliminated within 1 h, endorsing that inserting cobalt can improve the ZnO photocatalysis efficiency for water remediation.