Photocatalytic effect and Mössbauer study of iron titanium silicate glass prepared by sol-gel method

A relationship between the photocatalytic effect and the local structure of 50Fe2O3⋅ (50−x)SiO2⋅xTiO2 glass abbreviated as 50FSxTi prepared by sol-gel method was investigated by 57Fe-Mossbauer spectroscopy (FeMS), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible diffuse reflectance spectroscopy (UV-VIS). Mossbauer spectra of 50FSxTi glass before annealing showed a doublet with the isomer shift (δ) and quadrupole splitting (Δ) of 0.41±0.01 mm s−1 and 0.75±0.02 mm s−1, indicating that Fe3+ formed FeO6 octahedra (O h). A comparable δ of 0.36±0.02 mm s−1 and the larger Δ of 0.92±0.02 mm s−1 values were confirmed for 50FSxTi after annealed at 400 ∘ C for 3 h. These results indicates that the coordination number of iron polyhedra decreases from 6 to 4 due to annealing. UV-VIS diffuse reflectance spectra of 50FS10Ti yielded two optical band gap energies (E g’s) of 2.05 eV and 3.55 eV. This result implied that 50FS10Ti has two optical band gaps in the visible area and UV area. A bleaching test performed by 10 mL of MB aqueous solution and 40 mg of powder 50FS10Ti glass sample showed that MB absorbance decreased from 3.16 to 0.43 after UV-visible light irradiation for 2 h with the first order rate constant (k) of $1.6\times 10^{-2}~ \min ^{-1}$ . These results prove that titanium containing iron silicate glass with the composition of 50Fe2O3⋅40SiO2⋅10TiO2 has the UV and visible light responsive photocatalytic effect.