Influence of inorganic anions and organic additives on photocatalytic degradation of methyl orange with supported polyoxometalates as photocatalyst

A novel supported polyoxometalate (POM), phosphotungstic acid immobilized into yttrium-doped TiO₂ (HPW-Y-TiO₂) nano photocatalyst was prepared via sol-gel and impregnation method. The samples were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and N₂ absorption-desorption analysis. The results showed that the supported POM exhibited Keggin structure and anatase phase with large BET surface area. The influences of inorganic anions and organic additives on the photocatalytic degradation of azo dye methyl orange with HPW-Y-TiO₂ as photocatalyst under UV light (λ≥365 nm) were investigated. Results showed that inorganic anions Cl^-, SO₄^2-, CO₃^2- and NO₃^- had inhibition effect on the degradation of methyl orange. A great enhancement of degradation rate was obtained while H₂O₂ and ethyl alcohol were applied. The degradation rates improved with the increase of H₂O₂ concentration. The optimum additive amount of ethyl alcohol was 0.5 mol/L. The possible mechanisms of the effects of additives on methyl orange degradation were discussed.