Infra-red studies of adsorption at the solid/liquid interface

Abstract

The adsorption of cyclohexanone, propan-1-ol, decan-1-ol, and linoleic acid from carbon tetrachloride solution onto the surface of silica has been studied by infra-red spectroscopy. Cyclohexanone and the two alcohols adsorb via hydrogen-bonding interactions between surface silanol groups and the adsorbate molecules. For linoleic acid the primary adsorptive interaction involves hydrogen-bonding between surface silanol groups and the polar carboxylic acid groups. Evidence that the alkene bonds within the alkyl chain of linoleic acid undergo cis→trans isomerisation when adsorption occurs suggests that, at low coverages, the acid molecules are orientated such that the alkene groups are close to the oxide surface. Adsorption of acid dimers also probably occurs.