CTAB modified TiO2 supported on HZSM-5 zeolite for enhanced photocatalytic degradation of azophloxine

Abstract

A thin layer of titanium dioxide was supported on HZSM-5 zeolite via a sol-gel route. Cetyltrimethyl ammonium bromide (CTAB) was used to improve the porosity of the supported anatase TiO2. The influences of CTAB on the physicochemical properties of TiO2(n)/HZSM-5 composites were examined. The SEM and TEM images proved the loading of TiO2 layer on the surface of HZSM-5 zeolite. The absorption edge of TiO2(n)/HZSM-5 composite prepared using CTAB moved to longer wavelength region, and the bandgap energies of the composites were approximately 3.0 eV. Both the surface area and the pore volume of TiO2(n)/HZSM-5 composites were enlarged after using CTAB. Micropores were produced in the TiO2 layer after removing CTAB during the calcination process. The number of hydroxyl radicals produced under irradiation was in accordance with photocatalytic activity of the composites, and the photoluminescence intensity was also related to photocatalytic activity of the composites. The TiO2(3)/HZSM-5 sample obtained using 3 g CTAB had the maximum activity. The first order reaction rate constants for azophloxine degradation were 0.02823, 0.01842 and 0.01456 min−1 for TiO2(3)/HZSM-5, TiO2(0)/HZSM-5 and TiO2, respectively. The major organic groups in azophloxine molecule were degraded on TiO2(3)/HZSM-5 after 90 min of reaction.