Decomposition of nonionic surfactant on a nitrogen-doped photocatalyst under visible-light irradiation

A visible-light-active N-containing TIO2 photocatalysts were prepared from crude amorphous titanium dioxide by beating amorphous TiO2 in gaseous NH3 atmosphere. The calcination temperatures ranged from 200 to 1000 degreesC, respectively. UV-vis/DR spectra indicated that the N-doped catalysts prepared at temperatures <400 degreesC absorbed only UV light (E-g = 3.3 eV), whereas samples prepared at temperatures greater than or equal to400 degreesC absorbed both, UV (E-g = 3.10-3.31 eV) and vis (E-g = 2.54-2.66 eV) light. The chemical structure of the modified photocatalysts was investigated using FT-IR/DRS spectroscopy. All the spectra exhibited bands indicating nitrogen presence in the catalysts structure. The photocatalytic activity of the investigated catalysts was determined on a basis of a decomposition rate of nonionic surfactant (polyoxyethylenenonylphenol ether, Rokafenol N9). The most photoactive catalysts were those calcinated at 300, 500 and 600 degreesC. For the catalysts heated at temperatures of 500 and 600 degreesC Rokafenol N9 removal was equal to 61 and 60%, whereas TOC removal amounted to 40 and 35%, respectively. In case of the catalyst calcinated at 300 degreesC surfactant was degraded by 54% and TOC was removed by 35%. The phase composition of the most active photocatalysts was as follows: (a) catalyst calcinated at 300 degreesC-49.1% of amorphous TiO2, 47.4% of anatase and 3.5% of rutile; (b) catalyst calcinated at 500 degreesC-7.1% of amorphous TiO2, 89.4% of anatase and 3.5% of rutile; (c) catalyst calcinated at 600 degreesC-94.2% of anatase and 5.8% of rutile. (C) 2004 Elsevier B.V. All rights reserved.