Hydrothermal Synthesis Of La-doped Titanium Dioxides And Their Photocatalytic Activities

Titanium dioxide , a photocatalyst, has received a great deal of attention owing to its advantage such as long term stability, non-toxicity and low cost. Photocatalyst with higher activity and efficiency is an essential for its application in large scale, doped TiO₂ has been proved to be a simple and efficient route to improve the photoactivity. At present, rare-earth-doped TiO₂ were synthesized by several methods, which almost followed by calcination at elevated temperatures. The heat treatment is accompanied by sintering, grain growth, lack of surface defect and loss of surface area on catalyst particles that are known to reduce catalytic activity. The cheaper and simpler non-calcination preparation of TiO₂ photocatalyst with small particle size, large surface area, good crystallization and high photoactivity has been a significative research.In this paper, La-doped TiO₂ photocatalysts were synthesized via an improved hydrothermal synthetic route without calcination step, and were characterized by XRD, UV-Vis, IR and BET. The effect of ratio of water to alcohol, dopant content and reaction temperature on TiO₂ crystalline phase, crystallinity, and photoactivity for degradation of Rh B were discussed in detail. The results show that the La doping inhibited the phase transformation from anatase to rutile, and improved the optical absorption and surface area of catalysts, also could effectively enhanced the photoactivity. When ratio of water to alcohol was 1: 0, hydrotherm treatment was kept at 200℃ for 48 h, dopant content was 1%, the best result of photocatalysis degradation is received. The photoactivity degradation efficiency of La-doped TiO₂ was higher than pure TiO₂ by 24%.Solid superacid SO₄^2-/TiO₂-La₂O₃ was prepared by impregnation method. The catalysts were examined by XRD, UV-Vis and IR. Photocatalytic activity of catalysts was also studied here. The results indicated that the reaction activity was altered with the change of concentration and time of sulfuric acid soaking, roasting temperature and doping amount of La. When sulfuric acid soaking concentration was 2 mol.L^-1, soaking time was 6 h, roasting temperature was 500℃ and doping amount of La was 1%, Rh B was degraded by 92% in 1 h.