Azo dyes decomposition on new nitrogen-modified anatase TiO2 with high adsorptivity
ABSTRACT New vis active photocatalyst was obtained by the modification of commercial anatase TiO2 (Police, Poland) in pressure reactor in an ammonia water atmosphere at 100 °C for 4 h. The photocatalytic activity of new material was tested during three azo dyes decomposition: monoazo (Reactive Read), diazo (Reactive Black) and poliazodye (Direct Green). Obtained photocatalyst had new bands at 1430–1440 cm−1 attributed to the bending vibrations of NH4+ and at 1535 cm−1 associated with NH2 groups or NO2 and NO. UV–vis/DR spectra of photocatalyst had also insignificant decrease in visible region. Fluorescence technique was used for studying the amount of hydroxyl radicals produced on TiO2 surface during visible light irradiation. The hydroxyl radicals produced react with coumarin present in the solution to form 7-hydroxycoumarin which has fluorescent capacity. Photocatalytic activity of modified TiO2 was compared with commercial titanium dioxide P25 (Degussa, Germany). The photocatalytic activity of TiO2/N was higher than that of unmodified material and P25 under visible light irradiation. The ability for dye adsorption (Reactive Red) on photocatalyst surface was also tested. Unmodified TiO2 and P25 has isotherm of adsorption by Freundlich model, and nitrogen-modified TiO2 by Langmuir model. The presence of nitrogen at the surface of TiO2 significantly increased adsorption capacity of TiO2 as well as OH radicals formation under visible radiation.
SourceAvailable from: Kenji Katayama[Show abstract] [Hide abstract]
ABSTRACT: In this study, a photocatalytic plate bound to highly dispersible silica-doped titanium dioxide (SiT) on a trimethoxysilyl-propyldiethylenetriamine (dien)-coated glass plate (dien-plate) was newly synthesized, and was evaluated by a flow analytical (FA) system, which consists of a photocatalytic reactor and a spectrophotometer, to continuously monitor the absorbance of tested chemicals. The method was not required to collect any sample solution at a constant period. The SiT-dien-plate facilitated the photodecomposition of methylene blue (MB) and indigo carmine (InC) in aqueous solutions. Notably, MB was quantitatively photo-decomposed following 18 h of UV-light irradiation, related to the electrostatic adsorption of surface-bound particles. A water-treatment ability of visible-light-responsive vanadium-modified nitrogen/silica co-doped titanium dioxide fixed on the dien-plate was also evaluated by the FA system. It clarified to decompose MB and InC under visible-light irradiation. Finally, the decomposition of a humic substance dissolved from Middle West China peaty soils by the SiT-dien-plate under UV-irradiation was assessed as applying the FA system with a photocatalytic plate.Analytical Sciences 01/2014; 31(1):15-21. DOI:10.2116/analsci.31.15 · 1.40 Impact Factor
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ABSTRACT: While TiO2 has generated great interest in the removal of organic pollutants in recent years, the effect of the surface chemical property of TiO2 on the adsorption performance is unclear. Here, TiO2 samples were prepared in succinic (without hydroxyl group), malic (with one hydroxyl group) and tartaric acid (with two hydroxyl groups) by hydrolysis method and labeled as SU-TiO2, MA-TiO2 and TA-TiO2, respectively. Their adsorption performance for anionic dye-Acid Red G (ARG) and cationic dye-Methylene Blue (MB) was investigated. The adsorption study indicates that the adsorption amount of ARG or MB was proportional to the alkalinity or the acidity, which is related to the number of hydroxyl group of the used acids, of the as-prepared TiO2. Therefore, SU-TiO2 displayed the largest adsorption capacity for ARG, while TA-TiO2 had the highest adsorption capacity for MB. Furthermore, TA-TiO2 can be reused at least 5 times without losing its adsorption capacity.The results indicate that the adsorption mechanism involves in the electrostatic interaction and the electron acceptor-donor interaction.Chemical Engineering Journal 02/2015; 269. DOI:10.1016/j.cej.2015.01.109 · 4.06 Impact Factor
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ABSTRACT: A stable visible light photocatalyst has successfully been developed by doping titanium dioxide (TiO2) with Ca, Ce, and W. Various combinations were developed and tested. The photocatalyst, when subjected to visible light photocatalytic degradation of C.I. Acid red 1 (AR1) showed an excellent performance in comparison with the most acclaimed commercial TiO2 photocatalyst, Degussa P25. The photocatalytic process with the best developed photocatalyst is “initial-concentration”-dependent, as high initial concentrations of AR1 dye precluded the photon energy from reaching the photocatalyst, and hence reduced its degradation rate. Initial pH of dye solution exerts its influence on the visible light photocatalytic degradation of the dye. High initial pH 10 was detrimental to the process, while the process was controlled by adsorption at lower pH 3. The developed photocatalysts were characterized by X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, X-ray diffraction, N2 physisorption, surface scanning electron microscopy, and fourier transform infra-red spectroscopy. The results showed a red shift in the band gap of the tri-doped TiO2 from 3.2 to 2.94 eV indicating a shift in the onset optical wavelength from 387.19 to 421.43 nm.Desalination and water treatment 08/2014; 52(28-30). DOI:10.1080/19443994.2013.813009 · 0.99 Impact Factor