Micellar solubilization of multi-component non-aqueous phase liquids (NAPLs) by Tween 80

Abstract

Non-aqueous phase liquids (NAPLs) at contaminated sites often consist of multiple organic pollutants. In this study, the solubilization behavior of multi-component NAPLs was examined for the ternary mixtures of TCE-PCE-octane, PCE-o-xylene-octane, and hexane-octane-decane in Tween 80 solutions. In the TCE-PCE-octane mixtures, the most hydrophobic octane exhibited the enhanced solubilization compared with that predicted by the ideal behavior, but the least hydrophobic TCE showed the decreased solubilization. In reference to the ideal solubilization, PCE, the intermediate hydrophobic component in the mixtures, was less solubilized in an octane-rich region but more solubilized in a TCE-rich region. Similarly, in the PCE-o-xylene-octane mixtures, the relatively hydrophobic octane was preferentially solubilized, whereas the less hydrophobic PCE and o-xylene were outcompeted. The mutual effect on the solubilization between PCE and o-xylene was not significant due to the small difference in their hydrophobicity. Compared with the preceding NAPL mixtures, the hexane-octane-decane mixtures showed the lesser extent of the nonideal solubilization behavior, which might be attributed to the proximity in the hydrophobicity and molecular structure among these components. Thus, the nonideal solubilization behavior in NAPL mixtures was largely controlled by the relative hydrophobicity among NAPL components.