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

The adsorption of a range of aliphatic mono- and di-carboxylic acids to metal oxides has been investigated using in situ attenuated total reflectance infrared spectroscopy. Thin films of TiO2, ZrO2, Al2O3, and Ta2O5 were prepared by evaporation the aqueous colloid oxides on single reflection ZnSe prisms. Formic and acetic acids were found to bind to ZrO2 and Ta2O5, but showed no adsorption to TiO2 and Al2O3. The dicarboxylic acids, oxalic, malonic, succinic, adipic, maleic, and fumaric acids, were found to adsorb to each of the metal oxide substrates. Oxalic and malonic acids were coordinated via ester linkages involving both carboxylate groups. The longer chain dicarboxylic acids coordinated via bridging bidentate interactions through each carboxylate group. (C) 1999 Elsevier Science B.V. All rights reserved.