Reverse-micellar extraction for micellar-solubilized contaminant and surfactant removal

Decontamination of surfactant solutions is important for reusing the surfactant and improving the economics of surfactant-based subsurface remediation. Typical solvent extraction is not efficient for removing high equivalent alkyl carbon number (EACN) contaminants from surfactant solutions because the solvent itself will be highly soluble in the surfactant systems. Reverse-micellar extraction uses relatively hydrophilic solvents (e.g. alcohols) to treat surfactant solutions containing micellar-solubilized high EACN contaminants. The micelles break up and migrate into the solvent phase to re-aggregate as reverse micelles during the extraction. The contaminants released during breakup of micelles also partition into the solvent phase. The reverse micelles, which contain 'solubilized' water and aqueous contaminant, exist together with dissolved contaminant in the solvent phase. Decreased pressure distillation can be then employed to further separate the different components in the solvent phase to achieve final contaminant and surfactant separation. Decreased pressure distillation following a reverse-micellar extraction can significantly reduce the total energy consumption compared to a direct distillation of the solution. (C) 2001 Published by Elsevier Science B.V.