Spectroscopic Studies on the Degradation of Methylene Blue by Using TiO2 and TiO2 - (x) ZnFe2O4

Abstract

Titanium dioxide (TiO2) and nanocomposites of TiO2 – (x) Zinc Ferrite (ZnFe2O4); (x = 0.01, 0.04 and 0.06 mole fractions) have been synthesized by complex polymerization process involving peroxy species. The used nanometric ZnFe2O4 was previously prepared. The materials have been characterized through X-ray diffraction (XRD) and Electron Paramagnetic Resonance (EPR). Photo-catalytic action of synthesized materials has been evaluated by the Ultraviolet - Visible (UV-Vis) spectroscopy through degradation of pollution model Methylene Blue (MB). Optical thresholds have been measured by applying Ultraviolet - Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS). The addition of previously synthesized ZnFe2O4 contributes to the extension of photo-response in the visible range of light but this phenomenon differs from previous studies because it does not cause higher photo-catalytic action compared to TiO2 derived by the same method. UV-Vis DRS studies give reason to assume that the enhanced photo-catalytic action of ТiO2 - (X) ZnFe2O4 composites compared to that of TiO2 is probably due to the accidental inclusions of ferric ions in the lattice of TiO2, rather than charge transfer due to heterojunction band alignment, which was claimed in prior studies. The basis for this assumption is the appearance of absorption threshold of all composite materials around 450 nm, which is not typical, neither for Zn-ferrite nor for TiO2