Effects of calcination temperature on photocatalytic degradation of ofloxacin on Gd2Ti2O7/HZSM-5

Gd2Ti2O7 was supported on HZSM-5 zeolite by sol-gel method to investigate the effects of calcination temperature on the properties of the Gd2Ti2O7/HZSM-5 composite. The crystallization of pyrochlore Gd2Ti2O7 phase starts at 750°C, with the most preferred orientation at the (222) plane. The absorptions of the metal-oxide bondings in gadolinium titanate can be seen in the far infrared spectra of the crystallized Gd2Ti2O7. The shrinking band gap energy at high calcination temperature can be attributed to the growth of Gd2Ti2O7 grain. IUPAC type IV adsorption–desorption isotherm and type H3 hysteretic loop in the isotherms indicate mesoporous structure with broad pore size distribution in the Gd2Ti2O7/HZSM-5 composites. Adsorption of ofloxacin on the composite decreases with rising calcination temperature, which is in accordance to the change in surface area. The Gd2Ti2O7/HZSM-5 sample calcined at 800°C has the maximum activity on ofloxacin degradation. Well-crystallized Gd2Ti2O7 has good activity, while the shrinking surface area and porosity at high temperature are detrimental to its activity.