Interfacial Properties of Tridecyl Dimethyl Phosphine Oxide Adsorbed at the Surface of a Solution Drop in Hexane Saturated Air

Valentin B. Fainerman,Reinhard Miller,Eugene V. Aksenenko,Libero Liggieri,Alexander V. Makievski,Volodymyr I. Kovalchuk,Aliyar Javadi,Nenad Mucic

doi:10.3390/colloids4020019

Abstract

The surface tension of C13DMPO aqueous solution drops in hexane vapor is studied using the drop profile method. The hexane was injected into the measuring cell at three different conditions: before the formation of the solution drop, at a certain moment during the adsorption process, and after reaching the equilibrium of surfactant adsorption. The surface tension values for all experiments at the same concentration and different injection situations ultimately coincide with each other after attaining the final equilibration stage. The equilibrium surface tension isotherms of C13DMPO solutions, and the adsorption of both components—surfactant and hexane—were calculated. It was shown that the presence of surfactant leads to an increased hexane adsorption.

Highlights

The description of thermodynamics and kinetics of surfactant adsorption at aqueous solution–oil interfaces was presented, for example, in [1,2], respectively
The hexane was injected into the measuring cell at three different conditions: before the formation of the solution drop, at a certain moment during the adsorption process, and after reaching the equilibrium of surfactant adsorption
The results indicate that the water–alkane vapor interface represents an intermediate situation between the water–air and water–alkane interface because the presence of alkane molecules in the gas phase leads to co-adsorption or competition of the oil molecules

Summary

Introduction

The description of thermodynamics and kinetics of surfactant adsorption at aqueous solution–oil interfaces was presented, for example, in [1,2], respectively. The Langmuir [3] and Frumkin [4] adsorption models are the most frequently used ones for a quantitative analysis of experimental results For many surfactants, these classical models were successfully applied [5,6,7,8], and it was found that the surfactant molar area and the surface concentration depend on the chain lengths of the alkane. Concerning water–oil interfaces, systematic studies on the dynamics and thermodynamics of surfactant adsorption layers were performed for aqueous solutions in contact with alkane vapor, for example by Javadi et al [9]. A theoretical model exists for an approximated physical picture of the cooperative and competitive adsorption of the oil and surfactant molecules This model goes beyond earlier approaches that essentially assumed that the alkane molecules only fill the empty spaces between the chains of adsorbed surfactants [12,13]. The quantum chemical calculations confirmed the ratio of alkane to surfactant molecules at very diluted interfacial layers

Methods

Results

Conclusion