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 non-modified 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.