When two phase liquids are brought into contact, the interface thus formed possesses free surface energy. Thus surface energy is numerically equal to the interfacial tension. The interfacial tension is an important property of organic-water-surfactant systems. It is a key parameter in inter-phase hydrodynamic and mass transfer operations. The presence of contaminants in most industrial grade chemicals is inevitable. The aim of this work is to investigate the simultaneous adsorption of two well-known surfactants, Triton x-100 and dodecyltrimethylammonium chloride (DTMAC), at the interface of toluene/water, a recommended high interfacial tension system for liquid-liquid extraction. In this regard, solutions of surfactant mixture are generally used for investigation the influence of contamination in operating conditions. The mole fraction of the adsorbed compounds in the mixed adsorbed monolayer for these systems is estimated by the Non Ideal Binary Mixtures (NIBM) theory and the molecular interactions between the two surfactants in the monolayer are obtained.
