Photocatalytic degradation of various dyes by combustion synthesized nano anatase TiO₂

Abstract

The 8-10 nm pure anatase phase titania with 156 m²/g BET surface area was prepared by solution combustion method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and BET surface area. This catalyst was used for the photocatalytic degradation of various dyes such as heteropolyaromatic dye (Methylene blue), anthraquinonic dye (Alizarin S), and azoic dyes (Methyl red, Congo red, and Orange G). The effect of catalyst loading, initial concentrations of the dyes, pH, and transition metal doping on TiO₂ was investigated. Substitution of TiO₂ with transition metal had a detrimental effect on the photocatalytic activity. However, this inhibition effect was not observed with Pt impregnated TiO₂. This was attributed to the metals being in ionic state in metal substituted TiO₂ synthesized by combustion method, and zero state of metal in impregnated catalysts as evidenced by XPS study. The degradation of dyes was also investigated in solar exposure. The photoactivity of the combustion synthesized titania was higher than commercial TiO₂ (Degussa P-25) for both UV and solar exposure. The experimental data followed Langmuir-Hinshelwood (L-H) rate form and the kinetic parameters were obtained.