Prepatation And Characterization Of Iodine Doped Titanium Dioxide And It's Modification With Lanthanum

The preparation of I-TiO₂ and La-I-TiO₂ catalysts and their activity in the photocatalysis of C.I.Reactive Red 141(RR141) and oxalic acid were investigated,respectively.The phtotocatalytic degradation of RR141 in aqueous solution under visible light irradiation was investigated with I-TiO2 as the catalyst.The I-TiO2 catalyst had high photocatalytic activity for decolorization of RR141. The effects of operational parameters,such as catalytic dose,pH value, initial concentration of dye and bulk temperature were ascertained,and the conditions for maximum decolorization were determined.Under the irradiation of a 500 W dysprosium lamp,at 24℃,the best I-TiO₂ catalytic dose was 1.5 g/L and the best pH was 6.0.Under these conditions,when the initial dye concentration was 50 mg/L,about 99%decolorization,as determined by UV-visible analysis,was achieved after 6 h reaction. Intermediates formed during RR141 decolorization were detected by gas chromatography coupled with mass spectrometry(GC/MS) and ion chromatography(IC).On the basis of these results,we propose a tentative degradation pathway.A series of photocatalysts had been synthesized successfully by codoping TiO₂ with La and I(La-I-TiO₂).Structure and properties of the catalysts were studied by the X-ray diffraction(XRD), Brunauer-Emmett-Teller(BET) method,transmission electron microscopy (TEM),X-ray photoelectron spectroscopy(XPS),and UV-vis diffuse reflectance spectra.The prepared anatase phase La-I-TiO₂(mole ratio 20:20:100) calcined at 400℃had a remarkable absorption in the visible light range from 400-550 nm.The catalytic efficiency was tested by monitoring the photocatalytic degradation of oxalic acid under visible light irradiation.The photocatalytic activity of La-I-TiO₂ was significantly higher than that of I-TiO₂ in aqueous oxalic acid solution.The probable process of oxalic acid degradation was that it was first adsorbed onto the surface of the catalysts,where it reacted with valence band holes(h_vb⁺) and the surface-bound or adsorbed·OH radicals(·OH_ads) as well as reactive oxygen species(ROS) derived from oxygen reduction by photogenerated electrons,and finally converted into CO₂ and H₂O without any stable intermediate.