SOIL CLEAN UP BY INSITU SURFACTANT FLUSHING .6. RECLAMATION OF SURFACTANT FOR RECYCLE

Solvent extraction has been studied for use in reclaiming contaminated surfactant solutions for reuse in soil surfactant flushing in the remediation of hazardous waste sites. Hexane was used as the solvent to extract p-dichlorobenzene (DCB), naphthalene, and biphenyl from 25, 50, and 100 mM sodium dodecylsulfate (SDS) solutions in a continuous countercurrent flow column. The contaminant concentration in the aqueous SDS was followed with time, and the removal was modeled using an unsteady-state model which included diffusion kinetics. The mass transfer time constant was approximately 2 hours. The percent removal of DCB increased with increasing hexane flow rate and decreased with both increasing SDS flow rate and increasing SDS concentration. The concentrations of all three contaminants were reduced by about 90% or better. Extraction of contaminated SDS solutions with hexane appears to be an effective method for cleaning up these surfactant solutions for recycle.