Measurements and Modelling of the Micellization of Alkyl Benzyl Dimethyl Ammonium Chloride and Cetyl Trimethyl Ammonium Chloride in Various Aqueous Media at 298.15 °K

The critical micelle concentration (CMC) of two cationic surfactants "alkyl benzyl dimethyl ammonium chloride (BAC), and cetyl trimethyl ammonium chloride (CTAC)" in aqueous solution of different salts, cationic dye and cationic surfactant was measured experimentally at room temperatures (298.15 degrees K). Four methods; conductivity, refractive index, surface tension and UV spectroscopy has been used to determine the CMC values. The CMC was found to decrease as the concentration of salts increased. Also, it was found that CMC of (BAC) and (CTAC) increase in the order: pure water. 0.001 M. 0.01 M. 0.1 M. While it increases when the methylene blue (MB) is added to the aqueous solution. The thermodynamic parameters (Delta G(mic)degrees, alpha and beta) of the micellization processes indicated that the micellization process is going spontaneous in all cases. Different surface properties of the two cationic surfactants including excess surface concentration and minimum area per molecule were also calculated using the surface tension measurements. The Davies equation was applied to calculate the Hydrophilic-Lipophilic Balance (HLB) values of the two cationic surfactants (BAC) and (CTAC) theoretically. An important parameter (Setschenow constant) was used to describe the effect of adding salt on the micelle size and shape of surfactant in its solution. The results indicate that the order of the salt effect is inversely proportional to the order of CMC values in different salts.