Hollow Spherical Hierarchical MoO 3 /SiO 2 –TiO 2 Structures for Photocatalytic Decomposition of Organic Pollutant in Water

MoO 3 /TiO 2 –SiO 2 layered spherical composites with hierarchical structures have been synthesized via a template and sol-gel methods in which TOKEM-320Y anion exchanger was used as template. The properties of MoO 3 /TiO 2 –SiO 2 spherical composites were characterized by X-ray diffraction, Scanning electron microscopy, Energy-dispersive X-ray spectroscopy, 3D X-ray microtomography, N 2 sorption, Infrared and Raman spectroscopies and ultraviolet spectrophotometry. The photocatalytic activity of MoO 3 /TiO 2 –SiO 2 composites was evaluated by photocatalytic degradation of methylene blue (MB) aqueous solution under irradiated with an I 2 excilamp (λ max  = 312 nm) and its photoabsorption energy properties are related to the interaction between TiO 2 –SiO 2 and MoO 3 which occurs through oxygen in Ti-O-Mo and Si-O-Mo. The layered hierarchical structure results in lower oxygen vacancy concentrations in composites (0.0425) and a reduced bandgap width (2.58 eV in compare to 3.18 eV for MoO 3 spheres), which increases the composite's absorption of light in the visible light regime (λ absorption edge is 480.5 nm). Photocatalytic degradation of the MB dye followed the pseudo-first-order-kinetics. Degradation product analysis was done using the HPLC-MS technique. The dye degradation is initiated by demethylation of the molecule and lead to formation of azure A, B and C and thionin. The results showed that MoO 3 /TiO 2 –SiO 2 composites exhibited a much higher photocatalytic activity (rate constant is 0.0645 min ‒1 ) than that of MoO 3 spheres and other MoO 3 samples in the literature. This investigation demonstrates that MoO 3 /TiO 2 –SiO 2 layered spherical composites is a promising candidate material for photocatalytic decomposition of organic dyes in textile waste water which are considered as one of the greatest threats to the environment.