Direct Determination of the Distribution Coefficient of Tridecyl Dimethyl Phosphine Oxide between Water and Hexane

Abstract

Drop profile analysis tensiometry is applied to determine the distribution coefficient of a nonionic surfactant for a water/hexane system. The basic idea is to measure the interfacial tension isotherm in two configurations: a hexane drop immersed in the surfactant aqueous solutions at different bulk concentrations, and a water drop immersed into a hexane solution of the same surfactant. Both types of experiments lead to an isotherm for the equilibrium interfacial tensions with the same slope but with a concentration shift between them. This shift refers exactly to the value of the distribution coefficient.

Cooperative Effects in Surfactant Adsorption Layers at Water/Alkane Interfaces

“…Two methods were employed to determine the surfactant's distribution coefficient. Similarly to what was reported in [15], the interfacial tensions were measured of decane drops formed in the aqueous surfactant solution and of water drops formed in surfactant solutions in decane. From the two adsorption isotherms of a surfactant thus obtained, it was possible to determine the distribution coefficient via the ratio of concentrations in oil and water, respectively, at which the interfacial tension was the same.…”

“…Two types of adsorption systems were used: a decane drop immersed into the C 12 DMPO aqueous solution, and a water drop immersed into the C 12 DMPO solution in decane. To determine the distribution coefficient, a method based on the analysis of the transfer of C 12 DMPO between water and decane is also employed.Colloids Interfaces 2019, 3, 67 2 of 11 between the aqueous and oil phase is an additional feature, important for all systems containing non-ionics [14,15].The theoretical description of surfactant adsorption layers at water/oil interfaces started by applying classical models derived for the water/air interface [16]. The lattice theory later derived by Bahramian and Danesh [17] gives a relationship for the interfacial tension but does not specify the contribution of surfactant molecules to the properties of the interfacial layers.…”

“…In this way, we cannot only explain the decrease of the interfacial tension at very low surfactant concentration, but can also give a realistic composition of the adsorbed amounts of alkane and surfactant over the entire C 12 DMPO concentration range.In this study, the surfactant's distribution coefficient between the water and decane phases was determined. Similar to the experiments performed in [15], two series of measurements were performed with two types of systems: a decane drop in the C 12 DMPO aqueous solution, and a water drop immersed into the C 12 DMPO solution in decane. To determine the distribution coefficient, we employed the method proposed in [14].…”

“…Colloids Interfaces 2019, 3, 67 2 of 11 between the aqueous and oil phase is an additional feature, important for all systems containing non-ionics [14,15].…”

“…In this study, the surfactant's distribution coefficient between the water and decane phases was determined. Similar to the experiments performed in [15], two series of measurements were performed with two types of systems: a decane drop in the C 12 DMPO aqueous solution, and a water drop immersed into the C 12 DMPO solution in decane. To determine the distribution coefficient, we employed the method proposed in [14].…”