Enhanced photocatalytic activity of gadolinium titanate on ofloxacin degradation after supporting on HZSM-5 zeolite

Gadolinium titanate was supported on HZSM-5 zeolite by sol-gel method to prepare Gd2Ti2O7/HZSM-5 composite. Pyrochlore structured Gd2Ti2O7 is the solely phase of gadolinium titanate in both the unsupported Gd2Ti2O7 and the Gd2Ti2O7/HZSM-5, and the crystallite size of Gd2Ti2O7 slightly decreases from 32.3 to 31.6 nm after supporting. The supported Gd2Ti2O7 crystals do not intend to aggregate into large particles as those in the unsupported Gd2Ti2O7. The typical functional groups in Gd2Ti2O7, Gd2Ti2O7/HZSM-5 and HZSM-5 are observed in Fourier transform infrared/far infrared spectra. The ofloxacin adsorption efficiency on the Gd2Ti2O7 is 16.0%, and the efficiency is 16.8% on the supported Gd2Ti2O7/HZSM-5, while the amount of hydroxyl radical produced on Gd2Ti2O7/HZSM-5 under illumination is much more than the amount produced on Gd2Ti2O7. The reaction rate constants for ofloxacin degradation are 1.05 x 10(-2) and 3.52 x 10(-2) min(-1) on the pure Gd2Ti2O7 and Gd2Ti2O7/HZSM-5, respectively. Photocatalytic degradation efficiency increases almost linearly with rising Gd2Ti2O7 amount when Gd2Ti2O7 concentration is less than 400 mg L-1, and the maximum photocatalytic degradation efficiency occurs in the solution containing 10 mg L-1 ofloxacin.