Lanthanide Oxide Doped Titanium Dioxide Photocatalysts: Effective Photocatalysts for the Enhanced Degradation of Salicylic Acid and t-Cinnamic Acid

The photocatalytic degradation of salicylic acid and t-cinnamic acid has been investigated in aqueous suspensions of lanthanide oxide doped TiO2 photocatalysts. Complete mineralization has been achieved in the case of lanthanide oxide doped TiO2 photocatalysts in total contrast to the formation of intermediates in case of nonmodified TiO2. The equilibrium dark adsorption of salicylic acid and t-cinnamic acid is ca. three times and two times higher, respectively, on the lanthanide oxide modified catalysts as compared to the nonmodified TiO2 catalyst. The adsorption isotherms were analyzed in terms of the Langmuir theory and a good fit was obtained. The enhanced degradation is attributed to the formation of the Lewis acid–base complex between the lanthanide ion and the substrates at the photocatalyst surface. The concentration of the organic acids at the composite Ln2O3/TiO2 photocatalysts could provide a means for the enhanced activity.