Effects of Na2SO4 and Na3PO4 on the surface and thermodynamic properties of an anionic surfactant: bis-(2- ethyl hexyl) sodium sulfosuccinate (AOT) in aqueous solutions

Abstract

From tensiometric measurements, critical micelle concentration (CMC), maximum surface excess concentration, minimum area per molecule at the air-liquid interface and thermodynamic parameters of micellization have been determined for an anionic surfactant: bis-(2-ethylhexyl) sodium sulfosuccinate (AOT) in aqueous medium. Effects on the above physico-chemical properties due to added electrolytes: Na₂SO₄ and Na₃PO₄ over a wide range of the surfactant concentrations and at 288.15, 293.15 and 298.15 K have been described in the light of intermolecular interactions. The CMC of AOT is lowered and the micellar stability is improved upon mixing the above electrolytes in aqueous surfactant solution and the same become more pronounced when divalent SO₄^2- are replaced by trivalent PO₄^3-. These observations may be beneficial for improving efficiency of AOT as a detergent, managing oil spill problem, in froth-flotation process for concentrating ores and for efficient recovery of petroleum in the tertiary process.