Date of Award

1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

Dipak Roy

Abstract

Soil washing using surfactants is a promising alternative for the conventional pump-and-treat method of removing hydrophobic organic compounds. The interactions and the transport of the chemicals have been studied by batch and column experiments. Sodium dodecylsulfate (SDS), an anionic surfactant, and anthracene, a hydrophobic organic, were chosen as the representative surfactant and contaminant, respectively. Fine sand and native soil were used as formation media. The experimental results indicated that the maximum loss of SDS on native soil from the solution was observed when the aqueous SDS concentration was in the region of the critical micelle concentration, and this loss was even higher in the presence of NaCl. Injection of the test surfactants to the test soil matrices decreased the hydraulic conductivity. The mechanisms which could be responsible for this change are clay expansion, sodium dispersion, fine particle mobilization and precipitation of calcium and magnesium dodecylsulfate. For the soil used in this experiment, the precipitation of divalent salts of surfactants appears to be the primary reason for the reduction of hydraulic conductivity. Anthracene solubility in SDS solution were conducted in batch reactors. The results showed that the solubility of anthracene increased linearly with an increase in SDS concentration above the critical micellar concentration. Experiments verified that SDS can be effective in removing anthracene from contaminated sand mainly due to the solubility increase by micellization. The kinetics of anthracene solubilization was observed to follow the exponential Elovich equation. The mixing-cell concept was used to solve the mass conservative equations for contaminated sand columns. The apparent equilibrium isotherm between anthracene in SDS solution and the soil is a Langmuir type. The equilibrium model and non-equilibrium model developed in this study can predict the SDS and anthracene breakthrough curve, respectively, using independently measured parameters.

Pages

173

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