Charge number effect on the miscibility of inorganic salt and surfactant in adsorbed film and micelle: Inorganic salt–dodecylammonium chloride mixtures

Abstract

The effect of inorganic salts with different charge numbers of cations on the adsorption and micelle formation of dodecylammonium chloride (DAC) was clarified by applying the thermodynamic treatment of surfactant mixtures to mixtures of DAC with calcium and lanthanum chlorides and comparing the results with those of the sodium chloride-DAC mixture in the previous study. Surface tension of aqueous solutions of the salt-DAC mixture was measured as a function of the total molality of the mixture and the mole fraction of DAC in the mixture at 298.15 K under atmospheric pressure. Judging from the phase diagrams of adsorption and micelle formation obtained from the surface tension measurement, dodecylammonium cations expel inorganic cations from the adsorbed film and micelle and the repulsive interaction between dodecylammonium and inorganic cations increases with increasing charge number of the inorganic cation.

Probing the self-aggregation behavior and counter ion distribution of a copper surfactant complex

“…Therefore, it is possible that the negative adsorption of Cu 2+ due to electrostatic repulsion is greater at the surface of a micelle where a larger amount of positive charges are present as compared to the surface adsorbed film. A similar result 36 was obtained while exploring inorganic salt-dodecylammonium chloride mixtures. The dodecylammonium ion (DA + ) expelled inorganic cation from both the adsorbed film and the surface of micelle, and negative adsorption of metal ions in these systems was greater in micelles than in adsorbed films.…”

“…In addition, the repulsive interaction between DA + and the inorganic cation in the adsorbed film increased in the order Na + o Ca 2+ o La 3+ . 36 The absence of copper ions at the interface implies that there exists negative adsorption. Negative adsorption is usually observed for inorganic salts and is caused by repulsive image forces between ions in the solution and electrostatic images in the air phase as well as an ion-free layer formed by the hydration of ions.…”

Adsorption of Surfactant Ions and Binding of Their Counterions at an Air/Water Interface

“…Similarly, the addition of electrolytes remarkably reduces the surface tension of an aqueous solution of ionic surfactants. There are a lot of experimental studies on the surface tension of the mixture of ionic surfactants and electrolytes [5][6][7][8][9][10][11][12][13][14] . As can be readily speculated from the results of CMC, the drastic decrease in the surface tension may be closely related to the shielding effect of electrolytes.…”

Miscibility of sodium chloride and sodium dodecyl sulfate in the adsorbed film and aggregate

“…We then evaluated the composition of adsorbed film from the surface tension and obtained phase diagram of adsorption. The phase diagram was proved to be useful in clarifying the miscibility of inorganic salt and surfactant and the interaction between inorganic ions and the head group of surfactant in adsorbed films [ 8 – 13 ]. Furthermore, the adsorption and micelle formation have been studied separately in previous studies, even if the CMC was determined from the surface tension vs. concentration curve [ 4 , 7 , 14 , 15 ].…”

“…On the other hand, for salt–surfactant mixtures, we have determined the composition of the adsorbed film and micelle coexisting at the CMC from the dependence of mixture CMC and surface tension at the CMC on the bulk composition. We then compared the miscibilities of salt and surfactant in the adsorbed film and micelle by using the phase diagram for adsorbed film–micelle equilibrium [ 8 , 10 – 13 ].…”