Dysprosium-doped mesoporous TiO2 as an effective photocatalyst for the oxidation of methyl orange, o- and m-xylenes

Titanium dioxide samples doped with different amounts of dysprosium were synthesized with the sol–gel template method. The structure of the obtained materials was investigated by X-ray fluorescence, scanning electron microscopy, X-ray diffraction (XRD), diffuse reflection spectroscopy, low-temperature adsorption–desorption of nitrogen, and inductively coupled plasma mass spectrometry. According to XRD, it is assumed that Dy 3+ ions are statistically distributed in the titanium dioxide phase, predominantly located in interstices or on the surface of TiO 2 crystallites. The diffraction patterns show no peaks characteristic of the Dy 2 O 3 phase, the average sizes of crystallites of doped samples decreased compared to the sizes of undoped samples from 16.9 to 7.0–7.6 nm, and the crystal lattice parameters of the obtained materials differ. The introduction of dysprosium into the structure of titanium dioxide reduced the energy of the band gap of the obtained materials from 2.83 to 2.67–2.78 eV, which makes it possible to use them as catalysts for the photooxidation of methyl orange, o- and m-xylenes in water using the visible light. The maximum photocatalytic activity of the oxidation of methyl orange, o- and m-xylenes is characterized by a TiO 2 sample containing 9.5% dysprosium (Dy(9.5)/TiO 2 )—after 2.5 h the degradation of o- and m-xylenes on this catalyst was approximately 80 and 95%, respectively. The degradation of methyl orange on the (Dy(9.5)/TiO 2 ) sample was 73% after 3 h.