Hydrocarbon and alcohol effects on sulfonate adsorption on alumina

Adsorbed surfactant aggregates are finding applications in areas such as soil washing and ultrafiltration. In order to optimize these processes it is imperative to fully elucidate the effects of the solubilizates and additives on surfactant adsorption and aggregation. The effect of alcohol and hydrocarbon additives on the equilibrium adsorption of isomerically pure n-decylbenzene sulfonate on alumina is studied here. Dodecane increased sulfonate adsorption by more than one order of magnitude at concentrations of <10(-4) mol l(-1) sulfonate. At higher sulfonate concentrations the adsorption change was much less marked. The effects of varying the dodecane levels between 1 and 16.7 vol.% were surprisingly small. In contrast, addition of propanol decreased sulfonate adsorption under all conditions because the, alcohol increased the power of the solvent towards the surfactant. Medium and long chain alcohols were found to interact synergistically with the surfactant, decreasing the onset of both hemimicellization and micellization. Sulfonate adsorption increased in pre-micellar solutions but decreased in micellar solutions. In addition, adsorption of sulfonate was found to be identical at low levels of decanol, both of which were well above the aqueous solubility limit. This suggested that the effect of the additive is limited by its solubility in the phase from which adsorption takes place.