Arrangement of SDS adsorbed layer on carbonaceous particles by zeta potential determinations

Measurements of the amount adsorbed of an anionic surfactant from aqueous solutions on activated carbons and carbon blacks, together with zeta potential determinations of the suspended particles, have been carried out. Changes in adsorption isotherms and zeta potential curves with the equilibrium concentration in solution present a similar behavior. Although the solids have different zeta potential when they are suspended in pure water, it has been found that the relative change of the zeta potential at the maximum adsorption for each solid is proportional to the areal amount adsorbed, this proportion being similar for all the samples despite of their surface area or porosity. These results indicate that adsorption of the anionic surfactant has to take place on parts of the surface which allow the ionic head to be exposed to the solution, probably the more inner parts of the surface being not allowable to the adsorbate.