ADSORPTION OF MIXTURES OF TWEENS WITH SODIUM DODECYL SULFATE AT THE INTERFACE OF SOLUTION –AIR

Abstract

The process of adsorption of Tween (Tween-40 and Tween-60) with sodium dodecyl sulfate at the interface of a binary solution of surfactants – air in a wide range of molar ratios of the components of the mixture (n (Tween-40) : n (sodium dodecyl sulfate) – 0,7 : 0,3; 0,5 : 0,5 and n (Tween-60) – n (sodium dodecyl sulfate) – 0,7: 0,3; 0,5 : 0,5; 0,3 : 0,7). In the adsorption of binary mixtures of Tweens – sodium dodecyl sulfate in the indicated range of their molar ratios, there is a synergistic decrease in the surface tension in the region of sufficiently dilute solutions. Calculated by the isotherms of adsorption a surface activity of binary mixtures Tween – sodium dodecyl sulfate with a decrease the mole fraction of Tweens from 0,7 to 0,3 monotonically decreases. The values of adsorption of the studied binary systems of surfactants in relation to individual Tweens and sodium dodecyl sulfate are higher in the case of small content in the solution anionic surfactant. Based on the values of the standard free energy of Gibbs adsorption, we can conclude that the adsorption of binary mixtures of surfactants is a thermodynamically more advantageous process than adsorption of individual surfactants at the interface of solution – air. At any ratio of components of mixtures of surfactants at the interface of solution – air, mixed adsorption layers are formed, which are somewhat enriched with more surface-active nonionic surfactant. The value of the parameters of the interaction between the Tweens and the sodium dodecyl sulfate is negative, indicating a strong attraction between the molecules and the ions of surfactant of different nature, and depend on the molar ratio of the components of the mixture and the length of the hydrocarbon radical in the molecule of Tweens.

Keywords

• адсорбція
• суміші поверхнево-активних речовин
• Твіни
• додецилсульфат натрію