In the current work, we discuss the mixed micelles and thermodynamic micellization of aqueous binary mixture of polyoxyethylene - 20 sorbitan-monododecanoate (Tween 20) as nonionic surfactant and Benzyldimethylhexadecyl ammonium chloride (HDBAC) as cationic surfactant using conductivity and surface tension (γ) estimations in the temperatures range (288 -318K). Critical micelle concentration (CMC) and variables of micellization, like the standard thermodynamic functions: Gibbs free energy (Δ𝐺𝑚 ⁰ ), enthalpyΔ𝐻𝑚 ⁰ ) and entropy (Δ𝑆𝑚 ⁰ ) were calculated using the variation of conductivity and γ with molar concentration and the variation of ln XCMC with temperature. The experimental CMC values were applied to calculate the mole fractions of surfactant in the mixed micelle (𝑋1 𝑚 ), the β parameter and the coefficient of activity f1and f2, using the equations proposed by Clint and Rubingh, which indicate the β parameter, is always negative. In addition, the results of thermodynamic parameters show that ΔG⁰m are negative for both individual and mixture of HDBAC-Tween20 surfactants and the values negatively increased with increasing temperature while its negative values decreasing with decreasing initial mole fraction of HDBAC.
Degree of Ionic Dissociation of Mixed Micelles in Aqueous Solutions of Cationic and Nonionic Surfactants
