Cooperative Effects in Surfactant Adsorption Layers at Water/Alkane Interfaces

Alexander V Makievski,Mykola V Nikolenko,Aliyar Javadi,Valentin B Fainerman,Eugene V Aksenenko,Altynay A Sharipova,Saule B Aidarova,Reinhard Miller

doi:10.3390/colloids3040067

Abstract

In the present work, the properties of dodecyl dimethyl phosphine oxide (C12DMPO) at the water/decane interface are studied and compared with those obtained earlier at the interface to hexane. To simulate the interfacial behavior, a two-component thermodynamic model is proposed, which combines the equation of state and Frumkin isotherm for decane with the reorientation model involving the intrinsic compressibility for the surfactant. In this approach, the surface activity of decane is governed by its interaction with C12DMPO. The theory predicts the influence of decane on the decrease of the surface tension at a very low surfactant concentration for realistic values of the ratio of the adsorbed amounts of decane and surfactant. The surfactant’s distribution coefficient between the aqueous and decane phases is determined. Two types of adsorption systems were used: a decane drop immersed into the C12DMPO aqueous solution, and a water drop immersed into the C12DMPO solution in decane. To determine the distribution coefficient, a method based on the analysis of the transfer of C12DMPO between water and decane is also employed.

Highlights

Studies on the adsorption of various types of surfactants at fluid interfaces have been frequently performed
The equilibrium interfacial tension for a water drop in the C12DMPO solution in decane is by 6–7 mN/m higher than that for the same C12DMPO concentration in the aqueous solution
It should be noted that the dynamics of adsorption from the surfactant solution in decane is different from that from the aqueous solution

Summary

Introduction

Studies on the adsorption of various types of surfactants at fluid interfaces have been frequently performed. Recent papers report on new features of adsorbed surfactant molecules [5,6,7,8,9,10,11] and new experimental methods, such as [12,13] in particular, where studies were performed at water/oil interfaces. It is very clear that the adsorption behavior of surfactants at the surface of an aqueous solution is rather different from that at the interfaces between these solutions and an oil phase. The distribution coefficient of non-ionic surfactants between the aqueous and oil phase is an additional feature, important for all systems containing non-ionics [14,15]

Methods

Results

Conclusion