Synthesis, characterization and photocatalytic activity evaluation of WO3, TiO2 and WO3/TiO2 supported on zeolite faujasite

Abstract

The present investigation is focused on the preparation, characterization, and photocatalytic activity evaluation of TiO2/zeolite, WO3/zeolite, WO3/TiO2/zeolite, and WO3/TiO2 composites. Zeolite fujasite (FAU) was synthesized by the hydrothermal method, while the semiconductor/zeolite composites by a straightforward physical mixture and calcination treatment. The photocatalytic activity of the materials was evaluated through the methyl orange (MO) degradation under near-UV irradiation (365 nm). The photocatalysts were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDX), UV–vis diffuse reflectance spectroscopy and nitrogen physisorption. Results indicated that TiO2, WO3, and Zeolite Y kept their crystalline phases after the preparation method. TiO2 and WO3 particles were distributed on zeolite surface. Also, no significant changes in the band gap energies of the photocatalysts were found. The surface area of zeolite FAU decreased with the addition of TiO2 and WO3. The best MO degradation under near-UV irradiation was obtained with WO3/TiO2 heterojunction and TiO2 P25, no synergistic effect was found between semiconductors and zeolite FAU. Additionally, the kinetic data of the photocatalytic elimination of MO with all photocatalysts under near-UV radiation was investigated with several models: Zero-order, First-Order, Second Order, Modified Freundlich and Parabolic Diffusion, they were consistent with Modified Freundlich model. The effect of initial pH and photocatalyst weight was explored for TiO2/Zeolite composite and it was found that the best MO degradation was obtained at natural pH of 10.3 and 0.2 g of composite was the optimal amount of photocatalyst. Finally, the positive hole formation in all photocatalysts was detected by UV–vis spectroscopy and it was discovered that the highest density of positive holes was obtained with TiO2/zeolite composite.