In situ infrared spectroscopic analysis of the adsorption of aromatic carboxylic acids to TiO2, ZrO2, Al2O3, and Ta2O5 from aqueous solutions

In situ infrared spectroscopy has been used to investigate the adsorption o f a range of simple aromatic carboxylic acids from aqueous solution to meta l oxides. Thin films of TiO2, ZrO2, Al2O3 and Ta2O5 were prepared by evapor ation of aqueous sols on single reflection ZnSe prisms. Benzoic acid adsorb ed very strongly to ZrO2, in a bridging bidentate fashion, but showed only weak adsorption to TiO2 and Ta2O5. Substituted aromatic carboxylic acids; s alicylic, phthalic and thiosalicylic, were found to adsorb to each metal ox ide. Salicylic and phthalic acids adsorbed to the metal oxides via bidentat e interactions, involving coordination through both carboxylate and substit uent groups. Thiosalicylic acid adsorbed to the metal oxides as a bridging bidentate carboxylate with no coordination through the thiol substituent gr oup. (C) 2000 Elsevier Science B.V. All rights reserved.