Degradation of organic pollutants using metal-doped TiO2 photocatalysts under visible light: a comparative study

Various concentrations of dopants such as Mn, La, and Mo (0.25%-0.1%) were doped into TiO2 particles. An improved sol-gel method was used to prepare these particles using titanium isopropoxide as a precursor and their photocatalytic activity was tested by studying the degradation of three different types of organic pollutants (acid blue 129, tinidazole, and metalaxyl). The prepared samples were characterized with standard analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV Vis spectroscopy. The XRD analysis suggests the anatase phase with a crystalline nature. The SEM image of undoped TiO2 exhibits high roughness and irregular shaped particles. The doped TiO2 particles showed smaller size than undoped TiO2 with regular shaped and high surface area. The doped TiO2 particles also show lower band gap energy than undoped. The photocatalytic results indicate that TiO2 with a dopant concentration of 0.75% for all metal ions shows the highest photocatalytic activity. Moreover, the Mn-doped TiO2 (0.75%) degraded metalaxyl more efficiently as compared with other studied pollutants.