Preparation And Catalytic Performance Of Rare Earths Modified Of Bi₂O₃-TiO₂ Coupled Semiconductors

Photocatalysis is sougth after by environmentalists because of its efficiency, energy convervation and no-secondary pollution. TiO2 is regarded as an ideal photocatalyst due to its strong oxidation, high stability, non-toxicity and cheapness. Unfortunately, its commercializa- tion is greatly restricted by the two bottleneck factors which include the low light efficiency and quantum yield. We prepare Bi2O3-TiO2 and rare earths modified Bi2O3-TiO2 composites for obtaining more avtive photocatalyst. Their structures and properties had been investigated as well as their photocatalytic activities. This dissertation consists of following contents.Bi2O3-TiO2 composites were prepared by sol-gel method, and their structures and properties were extensively characterized by TEM, HRTEM, XRD, Raman, FT-IR and UV-vis DRS. The characterization results revealed that Bi2O3 and TiO2 coexisted in the resulting samples. Compound with low amount Bi2O3 could not only inhibit the phase transformation from anatase to rutile and the crystal growth, but also widen TiO2 response range towards light. The highest photocatalytic activity was gotten when the ratio of n(Bi) : n(Ti) was 0.0175.Nd3+ modified of Bi2O3-TiO2 coupled composites were prepared by sol-gel method, their structures and properties were extensively characterized by thermal analysis, TEM, HRTEM, XRD, Raman, FT-IR and UV-vis DRS. The characterization results revealed that Nd2O3 attached to the surface of Bi2O3-TiO2. Compound with low amount Nd2O3 could increase the dispersion of Bi2O3-TiO2. The highest photocatalytic activity was gotten when the ratio of n(Nd) : n(Bi) was 25 %.La3+ modified of Bi2O3-TiO2 coupled composites were prepared by colloidal blending method, and their structures and properties were extensively characterized by TEM, HRTEM, XRD, Raman, FT-IR and UV-vis DRS. The characterization results that revealed amorphous- anatase was obtained at 300 or 350 oC, but the anatase was obtained at 400 or 450 oC. The absorption of La/Bi2O3-TiO2 in the visible light region would gradually weaken as temperature rose. The highest photocatalytic activity was gotten when the calcined temperature was 300 oC.The carbon and rare earths(La3+, Nd3+ or Gd3+) co-modified Bi2O3- TiO2 composites were prepared by colloidal blending method, and their structures and properties were extensively characterized by thermal analysis, XRD, SEM, EDS, elemental analysis, XPS, FT-IR and UV-vis DRS. The characterization results revealed that the crystal type of the spherical composites were anastase. The carbon and lanthanum were present in the form of coke and La3+ in the C/La-Bi2O3-TiO2, respectively. C/La-Bi2O3-TiO2, C/Nd-Bi2O3-TiO2 and C/Gd-Bi2O3-TiO2 contained 5.05 %, 4.26 % and 3.57 % carbon, respectively. They all had strong absorption in the visible light region. When the concentration of catalysts loading were 2.5 g/L, the decolorization rate of 25 mg/L methyl orange reached 94.3 %, 96.2 % and 97.5 % under the irradiation of the 500 W xenon lamp after 60 min, respectively. Their apparent rate constants were 2.1, 2.4 and 2.7 times higher than that of P25, respectively. The results of recycling showed that the photocatalysts were bacically stable.