Sol–gel synthesis of B-TiO2(20%)/HZSM-5 composite photocatalyst for azophloxine degradation

Abstract

Photocatalyst in the supported form is more meaningful in large scale wastewater treatment than using powder material. HZSM-5 zeolite was used to support boron-doped anatase TiO2 in a sol–gel route in this work. The supported B-TiO2(20%)/HZSM-5 composite photocatalyst has strong activity on azophloxine degradation. The crystallite size of anatase TiO2 slightly increased from 6.1 to 8.4 nm when calcination temperature rose from 350 to 450 °C. The bandgap energies were around 3.3 eV for the composites calcined between 350 and 600 °C. The adsorption–desorption isotherm of the composites was the type IV isotherm for mesoporous material. The porous structure in the supported B-TiO2 layer was responsible for the variations of both BET surface area and pore volume in the composite. The maximum photocatalytic activity was obtained on the sample calcined at 450 °C. After 30 min of irradiation, 61.8% of the initial azophloxine molecules were degraded on the material. The first order reaction rate constant was 0.06168 min−1. Photocatalytic degradation efficiency was enhanced with increasing B-TiO2 concentration when the B-TiO2 dosage was below 400 mg/L.