Infrared study of the desorption of polycondensed aromatic compounds by non-ionic surfactants at the silica–carbon tetrachloride interface

Abstract

The desorption of two polycondensed aromatic compounds (9,10-diphenylanthracene and 3-acetylphenanthrene) by octylphenolethoxylates (type Triton X) at the silica–carbon tetrachloride interface has been studied by infrared spectroscopy. A correlation has been found between the adsorption of the surfactant on the free hydroxyl groups of silica and the desorption of the aromatic species. The results show that the adsorption mechanism of the Tritons is not deeply modified by the compound to be desorbed. The desorption process occurs when one or more surfactant segments are adsorbed on the sites, thus retaining the aromatic molecule. Then complete desorption can only be obtained if the surfactant is able to cover every surface site. This is achieved at increasing coverage by a decrease in the number of oxyethylenic segments per molecule which adsorb on the vacant and non-vacant sites.