Solubilization rates of n-alkanes in micellar solutions of nonionic surfactants

Accurate prediction of surfactant-enhanced recovery of organic contaminants in soils requires estimates of micellar solubilization rates. This study e xamines the influence of surfactant properties on the rates of solubilizati on of octane, decane, and dodecane in micellar solutions of a homologous se ries of purified dodecyl alcohol ethoxylates and two commercial surfactants , an ethoxylated linear alcohol (Witconol SN-120) and an ethoxylated sorbit an ester (Witconol 2722). A batch mixing technique was employed to investig ate these solubilization rates. For all surfactants studied, solubilization rates were found to increase with a decrease in solute chain length. For t he purified surfactants, solubilization rates also increased with ethoxylat e chain length. Batch concentration data were fit with a linear driving for ce mass transfer model. Effective mass transfer coefficients determined fro m these data ranged over more than one order-of-magnitude for the systems e xamined (0.11-3.3 h(-1)). Correlations developed for the effective mass tra nsfer coefficients exhibit a dependence on the solute micelle-water partiti on coefficient, solute molar volume, and surfactant hydrophile-lipophile ba lance or ethoxylate chain length. Although the measured coefficients are sp ecific for this experimental system, the results demonstrate the importance of employing organic and surfactant properties in the estimation of solubi lization rates.