Adsorption of Equimolar Mixtures of Cationic and Anionic Surfactants at the Water/Hexane Interface

Nenad Mucic,Jaroslav Katona,Emanuel Schneck,Eugene V Aksenenko,Reinhard Miller,Lidija Petrovic,Valentin B Fainerman,Sandra Bucko,Jelena Skrbic

doi:10.3390/colloids5010001

Nenad Mucic, Jaroslav Katona + Show 7 more

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https://doi.org/10.3390/colloids5010001

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Abstract

In mixed solutions of anionic and cationic surfactants, called catanionics, ion pairs are formed which behave like non-ionic surfactants with a much higher surface activity than the single components. In equimolar mixtures of NaCnSO4 and CmTAB, all surface-active ions are paired. For mixtures with n + m = const, the interfacial properties are rather similar. Catanionics containing one long-chain surfactant and one surfactant with medium chain length exhibit a strong increase in surface activity as compared with the single compounds. In contrast, catanionics of one medium- and one short chain surfactant have a surface activity similar to that of the medium-chain surfactant alone. Both the Frumkin model and the reorientation model describe the experimental equilibrium data equally well, while the adsorption kinetics of the mixed medium- and short-chain surfactants can be well described only with the reorientation model.

Highlights

IntroductionDetergents are made of surfactants [1], but in other applications like food processing [2], production of pharmaceuticals [3,4] or cosmetics [5] they cannot be replaced by other substances
Surfactants are important substances in almost every industrial technology
The aim of the present work is to determine the interfacial activity of catanionics formed by surfactants with unequal chain lengths, i.e., we investigate sodium alkyl sulphates (NaCn SO4 ) and alkyl trimethylammonium bromides Cn TAB with short (C6 ), medium (C12 ) and long (C16 ) alkyl chains

Summary

Introduction

Detergents are made of surfactants [1], but in other applications like food processing [2], production of pharmaceuticals [3,4] or cosmetics [5] they cannot be replaced by other substances. The use of a single surfactant type is often insufficient to tailor the product properties so that mixtures of surfactants are often used. Their interfacial behaviour can be predicted from the interfacial properties of the single components. In [6] a thermodynamic model was derived to describe the equilibrium adsorption layer characteristics of mixtures of non-ionic surfactants with other surfactants, ionic or non-ionic. The adsorption kinetics of mixed surfactant solutions was studied and a generalized Frumkin model was proposed

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