Sub-CMC Solubilization of Hydrocarbons By Surfactants.

Alkane solubilization by surfactants at concentrations lower than critical micelle concentration (CMC) was investigated using both batch and 2-D flow cell experiments. The results of batch experiments show that SDBS, Triton X-100, and rhamnolipid can enhance solubilization of alkanes at concentrations significantly lower than CMC, and that the molar solubilization ratio is higher than at hyper-CMC concentrations. The results of dynamic light scattering and cryo-TEM tests demonstrate that the sub-CMC alkane solubilization is based on an aggregate formation mechanism. The size of the aggregates decreases with increasing surfactant concentration, due to increase of surfactant access at the surface of the aggregates. The results of the 2-D flow cell experiments show that surfactants at sub-CMC concentrations caused enhanced dodecane solubilization. Surfactant aggregates were detected in the effluent using both dynamic light scattering and cryo-TEM methods. These results indicate a potential cost-effective strategy for surfactant-enhanced aquifer remediation (SEAR), employing low concentrations of surfactants to overcome the drawbacks of using surfactants at hyper-CMC concentrations.