Photocatalytic degradation of methyl orange by polyoxometalates supported on yttrium-doped TiO₂

A series of novel photocatalysts, H₃PW₁₂O ₄₀-Y-TiO₂ nanocomposites with different H ₃PW₁₂O₄₀ loading levels (10-40) were prepared by impregnation method. And the Y-TiO₂ support, doped with yttrium, was synthesized via sol-gel technique. The prepared catalysts were characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), nitrogen adsorption-desorption analysis and scanning electron microscopy (SEM). The processes allowed obtaining Keggin structure and crystallized anatase with large BET surface area as well as uniform distribution. The effects of H₃PW₁₂O₄₀ loadings, catalyst dose, initial pH and concentration of dye solution on the degradation kinetics of methyl orange under UV light (λ≥ 365 nm) were discussed. Kinetics studies showed that the photocatalytic degradation of methyl orange fitted the apparent first-order reaction. Methyl orange was totally degraded in 21 min under optimum conditions: 20 loading, 0.03 g dose and pH 1.0. The catalyst was stable and easily to be separated from reaction system for recovery.