In situ infrared spectroscopic analysis of the adsorption of aromatic carboxylic acids to TiO 2, ZrO 2, Al 2O 3, and Ta 2O 5 from aqueous solutions

Abstract

In situ infrared spectroscopy has been used to investigate the adsorption of a range of simple aromatic carboxylic acids from aqueous solution to metal oxides. Thin films of TiO 2, ZrO 2, Al 2O 3 and Ta 2O 5 were prepared by evaporation of aqueous sols on single reflection ZnSe prisms. Benzoic acid adsorbed very strongly to ZrO 2, in a bridging bidentate fashion, but showed only weak adsorption to TiO 2 and Ta 2O 5. Substituted aromatic carboxylic acids; salicylic, phthalic and thiosalicylic, were found to adsorb to each metal oxide. Salicylic and phthalic acids adsorbed to the metal oxides via bidentate interactions, involving coordination through both carboxylate and substituent groups. Thiosalicylic acid adsorbed to the metal oxides as a bridging bidentate carboxylate with no coordination through the thiol substituent group.