Cleaning of excavated soil contaminated with hazardous organic compounds by washing

Bench-scale experiments were conducted to investigate the effectiveness of an extraction and washing technique for the cleanup of contaminated soil using surfactants. The organics studied as model contaminants were 1,2,4-trichlorobenzene (TCB), aniline, phenol, and 2,4-dichlorophenol (DCP). A sandy loam was used as a model field soil. The results demonstrated the effectiveness of the extraction and washing process for decontamination of the sandy loam soil. As much as 99% of the organic contaminants studied were removed by the process depending upon the compound and the number of washes and rinses. The hydrophilic compounds-aniline, DCP, and phenol-were removed effectively from the soil by washing with deionized water alone. Surfactant washing had no advantage over water washing for these compounds. For the removal of TCB, a combination of washing with surfactant and rinsing with water was required. Alum coagulation was effective in separating clay and colloidal particles from the wash liquid but a relatively high alum dose was required and was observed to enhance adsorption of the contaminants on the clay particles. A small residual contaminant concentration remained in the soil.