Abstract :
[en] In order to limit the accumulation of organic contaminants in the environment, waste water
must be subjected to advanced pollution abatement processes such as photocatalytic
treatment. The aim of this research is the development of a TiO2-based photocatalyst with
enhanced characteristics compared to commercial Evonik P25. To reach this goal, TiO2-
based materials were synthesized by sol-gel from titanium and zirconium (0.7, 1.4, 1.6 and
2.0 mol%) alkoxides in water at ambient temperature. The peptization of the precursors was
carried out in presence of HNO3.
The physico-chemical characterizations showed that nano-crystalline anatase-brookite
particles were produced with the sol-gel process, with 4 times higher specific surface area
than P25. All samples presented a higher visible light absorption than P25. The XPS spectra
showed that all the samples were doped with nitrogen, due to the use of nitric acid, and that
mixed TiO2-ZrO2 oxide materials were obtained when doping with zirconia tert-butoxide.
Photoactivity was evaluated in the model reaction of p-nitrophenol degradation in water.
Under UV/visible light, the ZrO2 doping increased the degradation efficiency of the pure
TiO2 catalyst due to a better charge separation in the mixed TiO2-ZrO2 oxides, with
photoactivity higher than with P25. Under visible light, all samples were also much more
efficient than P25. This activity shift towards visible range was due to the N-doping of the
catalysts, with a further slight improvement for the Zr-doped ones.
Finally, the feasibility of producing films on steel substrate from an aqueous suspension of
the photocatalyst was assessed with P25, pure TiO2 and the best Zr-doped material, deposited
by bar-coating technique. The photoactivity of these films, evaluated in methylene blue
degradation under UV-A light in liquid phase, showed that the sample with the highest
dopant concentration had an efficiency 4 times higher than pure TiO2 and 20 times higher
than P25.
