Comparative study on the micelle properties of synthetic and dissolved organic matters

The conductivity of two synthetic surfactants and several natural surfactants, dissolved organic matters (DOMs), as well as their enhancement on phenanthrene solubility were measured in order to compare the formation of micelle by DOMs with synthetic surfactants, and their applicability for promoting hydrophobic organic pollutants' mobility. The DOMs could form micelle structure, similar to the synthetic surfactants. The critical micelle concentration values of the DOMs are lower than those of the synthetic surfactants, and the enhancement of phenanthrene solubility by the DOMs is comparable to or more remarkable than the synthetic surfactants. The partitioning coefficient of phenanthrene to DOM micelles decreased at high DOM concentrations, which is attributed to the structure rearrangement of DOM macromolecules, while no such phenomenon was observed for simple synthetic surfactant micelles. There was an optimum concentration range when applying DOMs to enhance HOCs' solubility and mobility. Synthetic surfactants gave a concentration dependent conductivity plot with two evident regimes, premicellar and postmicellar regimes, whereas the DOMs showed a gradual transition between the two regimes. The degree of counterion dissociation (α) of the DOMs was remarkably higher than those of the synthetic ionic surfactants. These results provide insight into DOM micelle structure and micelle forming process with compared to synthetic surfactants, and valuable information on using natural surfactant-enhanced remediation technology.