Correlation of the critical micelle concentration for aqueous solutions of nonionic surfactants

The critical micelle concentrations (cmc, mole fraction) for nonionic CiEj surfactants in aqueous solution were calculated in this study using a modified excess Gibbs energy model (m-Aranovich and Donohue (AD) model). This local-composition lattice model was derived in our previous study for correlating the limiting activity coefficients. The only adjustable parameter required in the m-AD model is the interchange energy. In surfactant system calculations, this parameter is found as a strong function of the physical properties of surfactants. A generalized correlation for the interchange energy is proposed in this investigation. Satisfactory cmc calculation results (mole fraction) are obtained for 37 systems. The m-AD model has less number of generalized parameters in comparison to the theoretically based method, and shows better accuracy than that from other activity coefficient models. Predictions of the cmc values (mole fraction) for mixed nonionic surfactants systems are also applicable using this m-AD model.