TiO 2/HZSM-5 nano-composite photocatalyst: HCl treatment of NaZSM-5 promotes photocatalytic degradation of methyl orange

Abstract

TiO 2/HZSM-5 nano-composite photocatalysts were prepared by dispersing TiO 2 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 TiO 2 could be found after supporting the TiO 2 on HZSM-5. Ti–O–Si bonds did not form between the HZSM-5 bulk and the supported TiO 2. Supported TiO 2 calcinated at 400 °C presented anatase structure. The titanium was in the oxidation state of Ti 4+, and the oxygen was in the form of O 2− in both TiO 2 and SiO 2. The adsorption ability and photocatalytic degradation activity of TiO 2/HZSM-5 nano-composite were better than that of bare TiO 2, accompanied with increasing specific surface area. Meanwhile, photocatalytic degradation activity of TiO 2/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 TiO 2/HZSM-5 photocatalyst was also investigated and methyl orange degradation rate was 82.4% of the initial rate after three recycles.