Partition coefficients of nonionic surfactants in water/n-alkane systems

Transfer of non-ionic surfactants across the water-oil interface: A molecular dynamics study

“…Despite the common nature of the driving force for surface activity in both types of environments, there is a certain distinction between the thermodynamic and the structural characteristics of the processes at the two types of interfaces [1]. The behaviour of surfactants at the water-air and water-oil interface has been studied both theoretically and experimentally in the recent years [2][3][4] because of the importance of such phenomena for industrial, electrochemical and pharmaceutical applications [5][6]. Most of these applications involve the formation of monomolecular layers of amphiphilic species at the interfaces [7] or the incorporation of surfactants into certain amphiphilic environments, for example cell membranes [8][9].…”

Experimental Investigation of Surfactant Partitioning in Pre-CMC and Post-CMC Regimes for Enhanced Oil Recovery Application

“…The tubes were shaken for 24 hours at high-temperature, giving enough time for the surfactant to partition from the aqueous phase into the oil phase and reach equilibrium. The aqueous solution was then transferred for analysis [8,20]. Oil and surfactant aqueous solution are two immiscible liquids, the ratio between their equilibrium concentrations is given by the partitioning or distribution coefficient k p , and it can be measured according to Equation (2).…”

“…In surfactant-based water/oil systems, the ratio between the surfactant concentration in the oil phase and in the water phase under equilibrium conditions is known as the partitioning coefficient K p . The partitioning of surfactants between the two phases has crucial effects on the surfactant flooding process; as well as determining the partitioning coefficient required to offer a better understanding of the partitioning mechanism [8,19,20].…”

“…Different methods to determine the surfactant concentration in water and oil at equilibrium conditions were applied depending on the investigated regime. Numerous studies discussed the partitioning in the pre-cmc regime [8,19,20,27,29], as well as in the post-cmc regime [20,[30][31][32][33]. In the pre-cmc regime, a proposed method determining the portioning coefficient of surfactants was developed.…”

“…However, in the post-cmc regime, this method is not applicable since the surface tension of a surfactant solution will attain a constant trend above the cmc. Therefore, an analytical technique should be applied to determine the partitioning coefficients in the post-cmc regime, such as high-performance liquid chromatography (HPLC) [20].…”