Preparation And Synergistic Photocatalytic Activity Of Nano-TiO₂-based Composite Powder And Supported Materials

Based on a comprehensive review of the photocatalysis principle, aplication, factors affecting activity, preparation methods of a composite photocatalyst, and shortcomings of composite catalyst and practical application of photocatalytic technology development, a composite photocatalyst TiO2-coated on lava surface (TCLF) was prepared with high photoactivity. In this work, the porous lava acted as hard template, was pretreated in supercritical CO2 to synthesize double template. TiO2 sol was coated on double template by sol-gel method in ultrasonic. Subsequently TiO2 gel was calcinated with organic removal in pores of lava. The TiO2-coated lava surface (TCLF) was prepared by the above narrated methods. Meanwhile, TiO2-coated lava and Fe-doped TiO2 nanopowder were prepared by the sol-gel method.The chemical structrue, surface morphology and phase of these samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD),thermogravimetric-differential thermal analysis(TG-DTA), fourier transform infrared spectroscopy (FT-IR) and diffuse reflection spectrum (DRS). The photocatalytic activity of samples was evaluated by the degradation of methylene blue (MB)The apparent activity energies of TiO2 and Fe–TiO2 crystalline growth are 25.179 KJ/mol and 27.431 KJ/mol, respectively. Apparent activation energy of grain growth and crystal transition temperature increases for Fe-doped TiO2 samples. Activation energies of thermal decomposition of TiO2 and Fe–TiO2 are 13.743 KJ/mol and 9.024 KJ/mol, respectively. The crystallization process and the growing speed of crystalline of TiO2 are enhanced at a low temperature by the Fe ions doping.Fe doping retains crystalline growth of TiO2, improves thermostabilities of TiO2, shifts the excited wavelength of TiO2 to visible light regions, produces the high content of Ti3+ ions in composites, which is available of decrease recombination ratio of photo-generated current carrier and enhances photoactivity.The photocatalytic degradation process of methylene blue conformd to the first-order kinetic equation. The photoactivity of the one-coated sample is more than that of the two-coated sample for methlylen blue degradation.As increasing of solution initial pH value, the rate constant of methylene blue degradation will increase gradually and then decreased. When pH value is 8, the highest rate constant is 0.044min-1. Additionally, the rate constant is increased with increasing catalysts content in the experimental range.