Effect of pH on the adsorption of sodium dodecane-sulphonate at the alumina/water interface

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Abstract
Adsorption isotherms for sodium dodecanesulphonate adsorption on alumina have been determined as a function of pH and surfactant concentration. The results indicate that at a certain critical concentration or critical pH, the adsorption increases markedly through association of the hydrocarbon chains of surfactant molecules to form hemimicelles at the interface. The dependence of the isotherms on pH and solution concentration is interpreted in terms of the Stern–Grahame model of the electrical double layer. Adsorption behaviour in this system is controlled by a specific adsorption potential that varies with surfactant adsorption density in the Stern layer.