Effects of ZSM-5 Treatment on the Properties of Gd2Ti2O7-nHZSM-5 Composites for RBR-X3B Degradation

Gd₂Ti₂O₇-nHZSM-5 (GTO-nZ) composites are prepared using HZSM-5 zeolite via a sol–gel route. The hydrochloric acid concentration in zeolite treatment can affect the properties of GTO-nZ composites. GTO has a typical pyrochlore phase Gd₂Ti₂O₇, and HZSM-5 zeolite does not have noticeable influences on GTO crystal formation. The bandgap energies are 3.77, 3.73, 3.67, 3.65, and 3.64 eV for GTO-nZ composites when hydrochloric acid concentration is 0, 0.2, 0.3, 0.5, and 1 mol L⁻¹, respectively. The isotherms of GTO-nZ composites are classified as IUPAC type IV of mesoporous material, while the adsorbed nitrogen quantities on GTO-nZ composites are much larger than the nitrogen quantity on GTO. The small amount of HZSM-5 zeolite can improve the porosity of GTO in the composites, and the surface area of GTO in the composites is significantly enlarged. The hydrochloric acid concentration has an apparent influence on the photocatalytic degradation efficiency of GTO-nZ composites. RBR-X3B (Reactive Brilliant Red-X3B) degradation efficiency is enhanced with increasing hydrochloric acid concentration to the maximum value at 0.3 mol L⁻¹. The reaction rate constants are 2.03 × 10⁻², 9.1 × 10⁻³, and 3.1 × 10⁻³ min⁻¹ for GTO-0.3Z, GTO-0Z, and GTO, respectively.