Adsorption of Single Anionic Surfactants on Hydrophobic Surfaces

The adsorption of a series of linear alkyl sulfonates and linear alkyl sulfates on sulfonated polystyrene latexes of various surface charge densities was studied to provide a better understanding of the effects of surface charge on the adsorption of anionic surfactants. Direct measurement of the adsorbed amount via ion chromatography provided greater accuracy and precision than do indirect methods such as soap titration. Results indicate that in the region of surface charge densities between -3 and -7 µC/cm(2) the effects of surface potential on adsorbed amount are more complex than has been described in the past. Previous work hypothesized a steady decrease in adsorbed amount with increasing surface charge due to increased electrostatic repulsions. The data obtained in this investigation indicate local increases in the adsorbed amount, possibly a result of configurational rearrangements of the adsorbed surfactant leading to an increase in surface area available for adsorption.