The Co-doping Modification Of Different Types Of TiO₂ Materials And Their Photocatalytic Properties

Using composite surfactant templates polyoxyethylene (20) oleyl ether (Brij98) and cetyl trimethyl ammonium bromide (CTAB) as structure–directing agents, N/La, and N/Ce co–doped mesoporous TiO2 complex photocatalysts and films were synthesized successfully by a modified sol–gel process using tetrabutyl titanate as the inorganic precursor, and urea, lanthanum nitrate and cerium nitrate as doping ion donors. The micromorphology of co–doped mesoporous TiO2 samples were characterized by X–ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), fourier transformed infrared spectroscopy (FT–IR), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), energy–dispersive X–ray spectrometer (EDS), X–ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption measurements. The XRD results indicated that all the the prepared complex photocatalyst were anatase. The TEM showed that the samples had mesoporous structures. The SEM indicated that the mesoporous TiO2 films possessed smooth surface. The FT–IR, EDS and XPS results showed that nitrogen, lanthanum and cerium had have been effectively doped into the titania lattice. The UV–Vis analysis revealed a red shift in the absorbing band edge within the range of 400–500 nm, which enhanced the usage of sunlight for the modified TiO2.The photocatalytic activities of samples were measured by photodecomposition of methyl orange (MO) and papermaking wastewater in both UV and visible light. The percent degradation of methyl orange (MO) was ca. 97.2% for the optimum co–doping of N(0.020)La(0.012)TiO2 under simulated sunlight irradiation for 9 h. The improvement of the photocatalytic activity was ascribed to the synergistic effects of the nitrogen and lanthanum co–doping. The mesoporous TiO2 sample with molar ratio of Brij98:CTAB=1:1 exhibited the highest photocatalytic activity for degradation of papermaking wastewater under ultra–violet light irradiation. The chemical oxygen demand (CODcr) percent degradation was about 73% in 12 h and chroma percent degradation was 100% in 8 h. The photocatalytic activities of mesoporous TiO2 flims were measured by photodecomposition of 2 mg·L-1 methyl orange, and the percent degradation was 100% after UV light irradiation 2 h.