Research Of Preparation And Photocatalytic Properties Of Titanium Dioxide Loaded On Zeolite

In this paper, titanium dioxide was synthesized by acid-catalyzed sol-gel method, and then metal ions doped TiO₂ photocatalyst supported on zeolite was obtained. The experimental results showed that, the photocatalytic activity of TiO₂ was improved through being loaded onto zeolite and doped with Fe³⁺.In the alcohol system, the sol for TiO₂ was prepared with tetrabutyl titanate as precursor, alcohol as solvent, and HCl as catalyst. The optimum photocatalytic activity of the samples was obtained after being calcinated at 500℃for 2h and at the condition that the volume ratio of tetrabutyl titanate: alcohol:H2O:HCl was 1:0.3:3:0.1.TiO₂/HZSM-5 nano-composite photocatalysts were prepared by dispersing TiO₂ onto the external surface of HCl-modified ZSM-5 zeolite using the sol-gel process. Effects of HCl modification on NaZSM-5 zeolite as a carrier of TiO₂ were investigated. Results showed that the adsorption ability and photocatalytic degradation activity of TiO₂/HZSM-5 nano-composites was better than that of bare TiO₂, giving the optimum value of 0.3mol/L. However, HZSM-5 zeolite was not of photocatalytic activity, the optimum photocatalytic activity for the samples with 30% TiO₂ was obtained after being calcinated at 400℃for 2h. The repeatability of photocatalytic activity was also tested and the decolorization rate was 82.4% of initial decolorization rate after four cycles. These materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) measurements. Results showed that modification of support by HCl did not change the surface morphology and structure of ZSM-5 zeolite. All the samples calcined at 400℃presented anatase structure. Supporting on HZSM-5 improved the dispersion of TiO₂, and restrained the increase of crystalline size. Ti-O-Si bonds were not formed between the HZSM-5 bulk and the supported TiO₂. The titanium was in the oxidation state of Ti⁴⁺, and the oxygen was in the form of O^2- in both TiO₂ and SiO₂.The results showed that doping of Fe³⁺ enhanced the photocatalytic activity of TiO₂ and 30%TiO₂/HZSM-5, and the optimum Fe³⁺ doping of Fe/Ti mole ratios for TiO₂ and 30%TiO₂/HZSM-5 were 0.05% and 0.07%, respectively. Doping Fe³⁺ did not change the surface morphology of TiO₂ and 30%TiO₂/HZSM-5, but inhibited phase transformation of TiO₂ from anatase to rutile, Ti-O-Si bonds were not formed between the HZSM-5 bulk and the supported TiO₂ either.