Solvent extraction and tandem dechlorination for decontamination of soil

The United States Environmental Protection Agency (US EPA) guidelines allow removal of polychlorinated biphenyls (PCBs) from soils via solvent extract ion. This option holds promise for removal of other recalcitrant organic co ntaminants as well. A study was undertaken to evaluate the effectiveness of solvent extraction with two tandem degradation techniques. The degradation techniques were chemical dehalogenation with immobilized reagents and gamm a -ray irradiation. The integrated approach was evaluated with contaminated soils from wood treatment and electric power substation sites. Evaluations were carried out on a bench scale in the laboratory and on a semi-pilot sc ale at a contaminated site. Binary solvent mixture of alkanes and alcohols yielded the highest extraction efficiencies. Extraction efficiencies in exc ess of 90% were obtained for PCBs, polychlorinated dibenzo-p dioxins (PCDDs ) and polynuclear aromatic hydrocarbons (PAHs), Extracted PCBs were rapidly degraded through chemical dehalogenation or with high doses of the gamma - ray irradiation. The residual organics in the solvent mixture were removed with activated carbon, and the solvent was recycled for subsequent soil ext ractions. Contaminants adsorbed on the activated carbon were destroyed with a counter flow oxidation process. (C) 2001 Elsevier Science Ltd. All right s reserved.