Smirnova O. Influence of the nature of adsorbate and solvent on interaction of phenoxycarboxylic acids with the silica surface

The influence of the nature of solvent and silica surface modification (using hexamethyl disilazane) on adsorption of oxycarboxylic acids has been studied. Using quantum-chemical calculations the relationship between adsorption and salvation effects was detected. For the first time it was shown that polarity and electron-donating ability of a solvent determine the magnitudes of Gibbs free energy and adsorption of oxycarboxylic acids. The dependencies of adsorption and desorption of oxycarboxylic acids on degree of surface modification were determined. The mechanism of adsorption of oxycarboxylic acids on silica surface was supposed. It was established that carboxylic acids react with surface sites via both hydrophylic and hydrophobic mechanisms. For the first time the dependency of adsorption of hydroxy-cinnamic acids and pyrocatechol on pKa on methylated silica surfaces was measured. The structure of adsorption complexes on silica surfaces for the self-associated acids was established.