Jiang Xiaoyuan

TiO₂ was prepared by the hydrolyzation method in (NH₄)₂SO₄-modified TiCl₄ solution, and TiO₂ photocatalysts were obtained by accelerating the precipitation of TiO₂ powder in a high-temperature water bath. The photocatalysts were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Raman spectrum and UV-Vis (Ultraviolet-Visible) spectrometry techniques, and the photocatalytic activity in phenol-contaminated water was investigated. The results showed that photocatalysts calcined at 400 °C had a specific surface area of 138.2 m²/g and an average particle size of 9 nm, and a significant increase in thermal stability of anatase phase. At the calcination temperature of 700 °C, the crystal form of TiO₂ started to change into rutile (anatase: 97%, rutile: 3%). The activity of TiO₂ photocatalysts prepared with (NH₄)₂SO₄-modified TiCl₄ solution was markedly stronger than that without (NH₄)₂SO₄-modified TiCl₄ solution. Maximal photocatalytic activity was observed at the mole ratio of Ti:(NH₄)₂SO₄=1:2, the water-bath temperature of 90 °C and the calcination temperature of 700 °C.

Using Sn_xTi_1−x O₂ as carriers, CuO/Sn_0.9Ti_0.1O₂ and CuO/Sn_0.7Ti_0.3O₂ catalysts with different loading amounts of copper oxide (CuO) were prepared by an impregnation method. The catalytic properties of CuO/Sn_0.9Ti_0.1O₂ and CuO/Sn_0.7Ti_0.3O₂ were examined using a microreactor-gas chromatography (GC) NO+CO reaction system and the methods of BET (Brunauer-Emmett-Teller), TG-DTA (themogravimetric and differential thermal analysis), X-ray diffraction (XRD) and H₂-temperature programmed reduction (TPR). The results showed that NO conversions of Sn_0.9Ti_0.1O₂ and Sn_0.7Ti_0.3O₂ were 47.2% and 43.6% respectively, which increased to 95.3% and 90.9% at 6 wt% CuO loading. However, further increase in CuO loading caused a decrease in the catalytic activity. The nitrogen adsorption-desorption isotherm and pore-size distribution curve of Sn_0.9Ti_0.1O₂ and Sn_0.7Ti_0.3O₂ represented type IV of the BDDT (Brunauer, Deming, Deming and Teller) system and a typical mesoporous sample. There were two CuO diffraction peaks (2ϑ 35.5° and 38.7°), and the diffraction peak areas increased with increasing CuO loading. TPR analysis also detected three peaks (α, β and γ) from the CuO-loaded catalysts, suggesting that the α peak was the reduction of the highly dispersed copper oxide, the β peak was the reduction of the isolated copper oxide, and the γ peak was the reduction of crystal phase copper oxide. In addition, a fourth peak (δ) of the catalysts meant that the Sn_xTi_1−x O₂ mixed oxides could be reductive.