Enhancing effects during the interaction of cationic surfactants and organic pollutants with clay minerals.

The adsorption of aromatic compounds (2-chlorophenol 2-naphthol) in the presence of cationic C16-surfactants by different clays (kaolin, illite, and bentonite (montmorillonite)) from water was studied. — The cationic surfactants alter the adsorption properties of clays by means of surface hydrophobing, which leads to a drastic increase and acceleration of the adsorption of these aromatic pollutants. If the surface is densely covered by surfactant ions, high exothermic heats of displacement for 2-naphthol are found by microcalorimetry. X-ray diffraction measurements of the basal spacing proved the intercalation of 2-chlorophenol within the hydrophobic interlayers of C16-bentonite. At very high surfactant concentrations (c ≫ CMC) the decreased adsorption of 2-naphthol was explained by a competition for 2-naphthol molecules between micelles and hydrophobic adsorbed surfactant layer. [ABSTRACT FROM AUTHOR]