Solubilization and Microemulsification of Chlorinated Solvents Using Direct Food Additive (Edible) Surfactants

Surfactant enhanced subsurface remediation is being evaluated as an innovative technology to expedite contaminant extraction from the subsurface. Regulatory approval of this technology will likely be enhanced by use of surfactants with FDA direct food additive status (“edible” surfactants). This research establishes edible surfactant systems capable of solubilizing (via micellar partitioning) and microemulsifying (via middle phase microemulsions) chlorinated solvents (PCE, TCE, and trans 1,2-DCE). Micellar partition coefficients with edible surfactants are observed to be comparable to values previously reported for other surfactants, with solubilization increasing aqueous concentrations by one to two orders of magnitude for the chlorinated organics. Middle phase microemulsion formation is dependent on surfactant structure and cosurfactant concentration. Solubility enhancement in the middle phase systems (microemulsification) is at least one to two orders of magnitude higher than solubilization for the same surfactant concentration, but is much more sensitive to the surfactant system and the contaminant. In addition, successful microemulsion formation is seen to be a function of ground-water temperature and hardness, indicating the need to consider these and additional factors for successful design and implementation of surfactant enhanced subsurface remediation. This research thus establishes a variety of edible surfactant systems that can significantly expedite subsurface remediation of chlorinated solvents, and illustrates the importance of proper selection and design of surfactant systems.

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