TiO2/HZSM-5 nano-composite photocatalyst: HCl treatment of NaZSM-5 promotes photocatalytic degradation of methyl orange

TiO2/HZSM-5 nano-composite photocatalysts were prepared by dispersing TiO2 onto the surface of HCl-treated NaZSM-5 zeolite using a sol-gel method. These materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), BET surface area analysis and X-ray photoelectron spectroscopy (XPS) measurements. Photocatalytic activities of the supported catalysts were examined through methyl orange degradation under UV irradiation. The results showed that HCl modification of NaZSM-5 did not noticeably change the surface morphology and structure of the zeolite. Improved dispersion and restrained crystalline size of TiO2 could be found after supporting the TiO2 on HZSM-5. Ti-O-Si bonds did not form between the HZSM-5 bulk and the supported TiO2. Supported TiO2 calcinated at 400 degrees C presented anatase structure. The titanium was in the oxidation state of Ti4+, and the oxygen was in the form of O2- in both TiO2 and SiO2. The adsorption ability and photocatalytic degradation activity of TiO2/HZSM-5 nano-composite were better than that of bare TiO2, accompanied with increasing specific surface area. Meanwhile, photocatalytic degradation activity of TiO2/HZSM-5 changed remarkably when HZSM-5 supports treated with different concentrations of HCl were used, giving the optimum HCl concentration of 0.3 mol/l. The recycling of TiO2/HZSM-5 photocatalyst was also investigated and methyl orange degradation rate was 82.4% of the initial rate after three recycles. (C) 2010 Elsevier B.V. All rights reserved.