Functionalization of Ceramic Tiles with N-doped TiO2 and Their Photocatalytic Function Under UV or Visible Light Irradiation

In this work, tiles functionalized with N-doped TiO2 film has been studied in the discoloration of aqueous solution of methylene blue (MB) as staining agent in presence of visible or UV light to verify the photocatalytic antistain properties of the modified prepared titania. Functionalized tiles were prepared by a TiO2 sol, starting with titanium isopropoxide as titania precursor and urea as nitrogen source, via coating technique. Photocatalytic tests were performed at ambient temperature and atmospheric pressure using a properly designed steel reactor with a Pyrex window. The irradiation of photoreactor was realized by four UV lamps or light emitting diodes (LEDs) emitting in visible region, checking both discoloration, both TOC in the solution during the time. The coating method allows obtaining N-doped TiO2 in anatase phase and its deposited amount increased linearly as a function of the number of coating steps performed. The absorption properties evidenced the ability of TiO2 modified with nitrogen of exploiting the visible light emitted by blue LEDs. In the case of UV all the functionalized tiles showed remarkably photocatalytic activity reaching the total MB discoloration after about 24 h of irradiation. When samples are irradiated with visible light, raw tile and tile functionalized with undoped TiO2 showed similar reaction rate, while tile functionalized with N-doped TiO2 has presented a discoloration activity about two times faster, together with a very high TOC removal. Therefore, the obtained results clearly indicate that N-doped TiO2 film is able to exploit both UV and visible light.