Prediction of Critical Micelle Concentrations of Nonionic Surfactants in Aqueous and Nonaqueous Solvents with UNIFAC

Abstract

The UNIFAC group-contribution model is used to predict the critical micelle concentration (cmc) of nonionic surfactants in aqueous and nonaqueous solvents. For predicting the cmc, the phase-separation thermodynamic framework approach is used, where the micellar phase is approximated as a second liquid phase resulting from the liquid−liquid equilibrium between the solvent and the surfactant. The necessary activity coefficients are predicted by UNIFAC. The most promising UNIFAC model for this purpose was found to be the UNIFAC-Lyngby (Ind. Eng. Chem. Res. 1987, 26, 2274). To improve the results for surfactants containing oxyethylene chains, a new set of parameters was evaluated for this group, leading to still better cmc predictions for both water and organic solvents, as well as binary solvent systems.

Effect of Biologically Significant Metal Complex Additives on the Micellar Properties of SDS

“…This dual tendency is responsible for adsorption of surfactants at interfaces and for the formation of such aggregates as micelles. The hydrophobic part of the aggregate forms the core of the micelle, while the polar head groups are located at the micelle-water interface in contact with and hydrated by a number of water molecules [1][2][3].…”

“…We found that the CMC value decreased in the following order. calcium oxalate < calcium fluoride < calcium chloride < calcium acetate Ponganis et al [13] interpreted the turbidity observed in aqueous solutions of SDS containing [Cu(phen) 2 ] + (phen=1,10-phenanthroline) below the CMC occurred from ion pair formation between the metal chelate ion and the polar head groups of the surfactant anions. Meisel et al [14] compared the absorption spectra of [Ru(bpy) 3 ] 2+ (bpy=2,2′-bipyridine) in aqueous SDS solutions with those in aliphatic alcohols and observed evidence that [Ru(bpy) 3 ] 2+ interacted with the hydrocarbon part rather than the polar head group of SDS.…”

The UNIFAC model and the partition of alkyl and alkylphenol ethoxylate surfactants in the excess phases of middle phase microemulsions

“…The possibility of using the UNIFAC model, with different approaches, to predict CMC's has been evaluated by different authors [16,17,24]. One of the approaches assumes that surfactants and solvent are part of a mixture, which split into two liquid phases at some specific Gibbs free energy [16,17].…”

“…One of the approaches assumes that surfactants and solvent are part of a mixture, which split into two liquid phases at some specific Gibbs free energy [16,17]. Another approach consists in assuming a pseudo micellar phase solely composed by surfactants in equilibrium with a solution of surfactant monomers dissolved in the solvent (water in this case).…”

“…Through those studies it was found that the variables that influence the partition also determine the phase behavior of microemulsions [15]. Other studies involved the use of UNIFAC to predict the critical micelle concentration (CMC) of alkyl ethoxylate surfactants and their distribution between octanol and water liquid phases at equilibrium [2,4,5,16,17]. The UNIFAC model offers a convenient framework to simulate systems at equilibrium considering the shape and interaction contributions of the functional groups that conform the molecules in a particular solution via activity coefficients [18,19].…”