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Dye decomposition on P25 with enhanced adsorptivity

100%
Janus M., Wawrzyniak B., Tryba B., Morawski A.
Polish Journal of Chemical Technology
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2008
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vol. 10
|
issue 2
11-16
EN
The preparation method and the activity of the TiO2-P25/N doped photocatalyst based on commercial titanium dioxide (TiO2 Aeroxide® P-25 Degussa, Germany) are presented. For the TiO2-P25/N preparation TiO2-P25 and gaseous ammonia were kept in a pressure reactor (10 bars) for 4 hours at the temperature of 200°C. This modification process changed the chemical structure of the TiO2 surface. The formation of NH4+ groups was confirmed by the FTIR measurements. Two bands in the range of ca. 1430 - 1440 cm-1 attributed to bending vibrations of NH4+ could be observed on the FTIR spectra of the catalysts modified with ammonia and the band attributed to the hydroxyl groups at 3300 - 3500 cm-1, which were not reduced after N-doping. The photocatalytic activity of the photocatalysts was checked through the decomposition of two dyes under visible light irradiation. The modified TiO2 thus prepared samples were more active than TiO2-P25 for the decomposition of dyes under visible light irradiation.
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Effect of calcination temperature on photocatalytic activity of TiO2. Photodecomposition of mono- and polyazo dyes in water

75%
Mozia S.
Polish Journal of Chemical Technology
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2008
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vol. 10
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issue 3
42-49
EN
The presented studies have focused on the influence of TiO2 properties, such as crystalline phase, crystallite size and surface area, on the effectiveness of degradation of azo dyes in water under UV irradiation. Two monoazo dyes: Acid Red 18 (AR18, C20H11N2Na3O10S3) and Acid Yellow 36 (AY36, C18H14N3NaO3S), and one polyazo dye Direct Green 99 (DG99, C44H28N12Na4O14S4) were applied as model compounds. The photocatalysts were prepared from a crude titanium dioxide obtained directly from the production line (sulfate technology) at the Chemical Factory "Police" (Poland). The crude TiO2 was calcinated in air for 1-4h at the temperatures ranging from 600 to 800°C. The BET specific surface area of TiO2 decreased gradually with increasing the calcination temperature. The crude TiO2 exhibited specific surface area of 277 m2/g. In case of the catalysts heated at 600, 700 and 800°C the BET surface area amounted to 62.3-53.3, 33.4-26.8 and 8.9-8.3 m2/g, for the calcination time of 1-4h, respectively. The crystallite size of anatase increased with increasing heat treatment temperature and ranged from 19 to 53 nm, for the temperatures of 600-800°C, respectively. The catalysts annealed at 600 and 700°C contained primarily anatase phase (94-97%), whereas the photocatalysts heated at 800°C were composed mainly of rutile (97-99%). The highest effectiveness of azo dyes degradation was obtained in case of the photocatalyst calcinated for 1h at 700°C. The photocatalyst was composed mainly of anatase (97%) with crystallite size of 27 nm. The most effectively photodegraded was AR18, having the molecular weight of 640.4 g/mol. The most difficult to degrade was AY36 exhibiting the lowest molecular weight from all the dyes used (375.4 g/mol).
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