Micellization and synergistic effect in an aqueous solution of an AOS-TX100 mixture: before and after equilibrium in the presence of clay

Abstract

In this research, a novel surfactant mixture consisting of anionic (alpha olefin sulfonate [AOS]) and nonionic (TX100) type was developed. Possible synergistic effect in micelle formation in different mass ratios of the mixture (1:2, 1:1, and 2:1) was studied by surface tension measurement method. Rubingh's Regular Solution theory was used to evaluate the interaction parameters (β) and activity coefficient (f) for both binary mixture and single surfactants, before and after equilibrium in the presence of clay minerals (kaolinite and illite). The differences between experimentally obtained CMC values and ideally calculated values, showed nonideality of the mixtures. In addition, the lower CMC values of mixtures in comparison with individual surfactants were an indication of synergism. The synergistic effect was maintained before and after equilibrium with clay minerals. The β values of the mixture before equilibrium were in the range -1.5 to -2.6. However, after equilibrium with kaolinite, the values were in the range of -1.9 to -3.9 while after equilibrium with illite they were in the range -1 to -3. For the mixture, before and after equilibrium, the synergism became more severe as mole fractions of AOS increased in the mixture.