Adsorption enthalpies of sodium dodecyl sulphate onto carbon blacks in the low concentration range

Adsorption enthalpies of sodium dodecyl sulphate onto a set of carbon blacks from aqueous solutions in the low concentration range are presented. The surfactant was found to adsorb on the carbon surface exothermally in the whole studied coverage. From the calorimetric results and the analysis of the adsorption isotherms by a double Langmuir equation, a model of the adsorption mechanism in these systems is suggested. The adsorption of the surfactant onto the carbon blacks can be explained by two energetically distinct steps corresponding to the adsorption of SDS in two different types of porosity.