44    SURFACTANT SCRUBBING OF HAZARDOUS CHEMICALS
FROM SOIL
Janet Kickabaugh, Research Associate
Sara Clement, Graduate Research Assistant
Department of Civil and Environmental Engineering
University of Cincinnati
Cincinnati, Ohio 45221
Ronald F. Lewis, Microbiologist
U.S. EPA-ORD-HWERL
Cincinnati, Ohio 45268
INTRODUCTION
A lab scale study was conducted to examine the effectiveness of aqueous surfactant solutions for
decontaminating soil from a hazardous waste site. The soil used in this study was from the Chem-dyne
hazardous waste site in Hamilton, Ohio which was used to store and dispose of pesticides, chlorinated
hydrocarbons, solvents, waste oils, and other hazardous wastes from 1975 to 1980. Clean up of the
site was initiated in 1980 and most chemical drums were removed by 1983. Soil from the site still
remains to be decontaminated. The Chem-dyne soil used in this study was analyzed by gas chromatography for 11 chlorinated hydrocarbons (hexachlorobenzene, dichlorobenzenes, trichlorobenzenes,
hexachlorobutadiene, Aldrin, Endrin, Heptachlor, and Dieldrin). The soil contained a total of from
216 to 266 mg/kg of these compounds. Analysis for total chlorinated hydrocarbons (52 peaks)
indicated that the total concentration of all chlorinated hydrocarbons in the soil was approximately
2078 mg/kg.
Surfactants were used to promote solubilization of these chlorinated hydrocarbons from Chem-
dyne soil. One end of a surfactant molecule is polar (water soluble), while the other end is non-polar
(organic soluble) so that they promote aqueous solubilization of sparingly-water soluble compounds.
Anionic, nonionic, cationic surfactants and blends of these types were evaluated. Anionic surfactants,
the oldest group of commercial surfactants, are usually highly water soluble, but are sensitive to the
total ionic strength of the media. The negatively charged polar solubilizing group on anionic surfactants is usually a sulfonate, sulfate, or phosphate functional group. Cationic surfactants are a small
group of softening and coating agents with a positively charged solubilizing group which is usually an
amino or quaternary nitrogen functional group. Nonionic surfactants do not have a charge on their
solubilizing group. They are solubilized by hydrogen bonding at oxygen or hydroxy! groups in the
surfactant molecule. Nonionic surfactants usually contain the polyoxyethylene group as their solubilizing group and are now the most commonly used group of commercial surfactants in North America.
LITERATURE SURVEY
Literature on using surfactants for secondary and tertiary oil recovery indicates that a blend of two
surfactants, a surfactant and a co-surfactant, is more effective than a single surfactant used alone.
Therefore, it was decided to investigate blends of surfactants (nonionic-anionic and nonionic-
cationic) as well as anionic, nonionic, and cationic surfactants used alone.
Only a few references to using surfactants for scrubbing soils from hazardous waste sites or spills
are available. The concept is still in the lab stage of development. Huibregste et al. [1] developed a
mobile soil scrubber to wash contaminated soil. They used 0.1-1% solutions of nonionic surfactants
in laboratory shake jar tests to determine the effectiveness of different types of solutions in scrubbing
various contaminants (PCB, phenol) out of soils. Initial contaminant concentrations were quite high
(61-850 mg/L PCB and 1,000-20,000 mg/L phenol). Removal of phenol by surfactant solutions
ranged from 67-97%, while removal of PCB ranged from 20-37%.
377