Sol-gel synthesis of Gd2Ti2O7/HZSM-5 composite photocatalyst for ofloxacin degradation

Abstract

Pyrochlore structured Gd2Ti2O7 was supported on HZSM-5 zeolite by sol-gel method to prepare composite χGd2Ti2O7/HZSM-5. Crystal growth of Gd2Ti2O7 is constrained after loading on the surface of HZSM-5 zeolite. The band gap energies are 3.77, 3.75, 3.72, 3.60 and 3.37 eV for the χGd2Ti2O7/HZSM-5 composites containing 30%, 50%, 70% and 90% Gd2Ti2O7, respectively. The micropores in the χGd2Ti2O7/HZSM-5 mainly come from the HZSM-5 zeolite, and the supported Gd2Ti2O7 provides the majority of the mesopores. Besides the contribution of HZSM-5, the extra enlargements in BET surface area and total pore volume after supporting are due to the enhanced porosity in the Gd2Ti2O7 layer. Photocatalytic degradation efficiency greatly depends on the variation of Gd2Ti2O7 loading content in χGd2Ti2O7/HZSM-5. The degradation process obeys the first order reaction law, and the reaction rate constants are 1.05 × 10−2 and 3.52 × 10−2 min-1 on the pure Gd2Ti2O7 and 90%Gd2Ti2O7/HZSM, respectively.