Adsorption of Dodecylbenzene Sulfonate on Na+‐montmorillonite: Effect of Salt Impurities

Abstract The adsorption of purified dodecylbenzene sulfonate (ABS) on Na + ‐montmorillonite follows the Langmuir isotherm, reaching a maximum amount adsorbed which corresponds to the anion exchange capacity of the clay. When a commercial grade ABS (containing 60% Na 2 SO 4 ) is used, the adsorption process is more complex and occurs in two distinct steps. In dilute solutions, the salt impurity has a minor effect on adsorption and the result is essentially the same as that obtained for the purified surfactant. However, as the salt concentration is increased to a given value, enhanced adsorption due to hemimicelle formation occurs.