Role of Vanadia and Titania Phases in the Removal of Methylene Blue by Adsorption and Photocatalytic Degradation

Total removal of methylene blue (MB) over vanadia (V₂O₅) -modified titania (TiO₂) composite demonstrated that the V₂O₅ and TiO₂ phases played a vital role in the adsorption and photodegradation of MB, respectively. The 10 mol% of V₂O₅- modified TiO₂ (10V-TiO₂) showed the highest removal of MB, for example, 26- and 2-folds better adsorption capacity than that of undoped TiO₂ and V₂O₅, respectively. The presence of surface hydroxyl, pores, and the highest amount of V⁵⁺ species in 10V-TiO₂ could be responsible for the high adsorption of MB. V₂O₅ induced anatase to rutile phase transformation and shifted absorption properties of TiO₂ to the visible light region. Considering the rutile phase has lower bandgap energy (3.0 eV), its presence in the sample has enhanced the photodegradation of MB. The photodegradation of MB followed pseudo-second-order reaction. The reusability test elucidated that the photodegradation performance of 10V-TiO₂ was improved by 30-folds after the second cycle, with total MB removal due to the exposure of more TiO₂ to MB. (author)