Interfacial Interaction of Binary Mixtures of Surfactants Hexadecyl Benzylammonium Chloride (HDBAC) and Tween 20 in Aqueous Solutions

The surface adsorption properties of mixed binary surfactants containing hexadecyl benzylammonium chloride (HDBAC) and Tween 20 in aqueous solutions were studied at different temperatures (288-318K) using tensiometry techniques. The interaction parameters and surface activity for both individual and mixed surfactants systems, the Critical Micelle Concentration (CMC), maximum surface excess concentration ( Γ max ) and minimum surface area per surfactant molecule ( A min ) at the air-water interface were determined. Also, the parameters related to synergism in surface activity such as adsorption efficiency (pC 20 ) and CMC/C 20 were calculated. The results obtained reveal that the binary mixed system possess CMC values lower than its components and these values decrease with increasing the concentration of Tween 20 in the solution. This behavior shows non-ideal synergism of the mixing process. The values of molecular interaction parameters β σ and the mole fraction of components at the air-water interface X 1 σ are calculated on the basis of Rosen’s model and showed that the interaction parameter of the adsorbed monolayer is always negative and has a higher negative value for 0.9 Tween mole fractions.