Foaming in aqueous solutions of mixtures of a zwitterionic and a cationic surfactant in presence of an electrolyte

Abstract

This paper reports the foamability and the stability of foams of aqueous solutions of mixed systems of a zwitterionic surfactant (i.e. N-Dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate) and a cationic surfactant (i.e. cetyltrimethylammonium bromide) in the presence of NaCl. The synergism between the surfactants was examined by measuring the surface tension for various compositions of the surfactants and the salt. The interaction occurring between the surfactant molecules adsorbed at the air–water interface influenced the monolayer properties. The mixed surfactant system produced a significant decrease in surface tension as compared to the single surfactant systems. In the presence of salt, the surface tension reduction was larger. The interaction among the surfactant molecules at the air–water interface and the same in the mixed micelles was quantified by the respective interaction parameters. The blender test was used to investigate the foamability and foam stability. The foamability studies showed synergistic behavior inasmuch as higher foam volumes were generated in the mixed surfactant systems as compared to the single surfactant systems. The addition of salt had a remarkable effect on the foaming properties of the mixed surfactant systems. It increased the stability of foams significantly. The synergism between the surfactant molecules had a notable influence on the zeta potential at the air–water interface.

Graphical Abstract

Keywords:

• Adsorption
• foamability
• foam stability
• synergism
• zwitterionic surfactant