figuration in which they adsorb. Measurements of adsorption The adsorption of a series of linear alkyl sulfonates and linear isotherms will yield the adsorbed amount, while an underalkyl sulfates on sulfonated polystyrene latexes of various surface standing of the features of the isotherms can lead to a better charge densities was studied to provide a better understanding of understanding of the configuration. This adsorption is conthe effects of surface charge on the adsorption of anionic surfactrolled by many factors, including the nature of the adsorbing tants. Direct measurement of the adsorbed amount via ion chromasurface (i.e., degree of hydrophobicity, ionic nature, radius tography provided greater accuracy and precision than do indirect of curvature), the structure of the surface active materials methods such as soap titration. Results indicate that in the region (character of the lyophobic and lyophilic portions of the of surface charge densities between 03 and 07 mC/cm 2 the effects of surface potential on adsorbed amount are more complex than molecules), properties of the bulk fluid phase (i.e., electrohas been described in the past. Previous work hypothesized a lyte concentration), and the temperature.
steady decrease in adsorbed amount with increasing surface charge The amount of material adsorbed is closely related to the due to increased electrostatic repulsions. The data obtained in hydrophobicity of the surface with more surfactant adsorbed this investigation indicate local increases in the adsorbed amount, as the surface becomes more hydrophobic (5). Surface hypossibly a result of configurational rearrangements of the adsorbed drophobicity can be changed by altering the surface charge surfactant leading to an increase in surface area available for density of the adsorbing surface. Changes in the surface adsorption. α§ 1996 Academic Press, Inc.
charge density also give rise to changes in the electrostatic interactions between the adsorbing surface and the adsorbing species. When anionic surfactants adsorb onto surfaces containing chemically bound anionic groups, electrostatic repul-* To whom correspondence should be addressed.
This study was initiated in order to gain a better under-171