Decontaminating PCBs from soils

Decontaminating PCBs from Soils, Sludges and Surfaces... 

PCBs, PCB-contaminated soils, CAHs and CAH-contaminated soils (as received clay loam and sandy soils) were readily decontaminated in om laboratory with Na/NHa at ambient temperature. Example decontaminations of PCBs from soils are illustrated in Table 1. Typically, the soil is slurred in liquid NHs and then metallic Na is added. No special effort is made to dry the soil. Soil slurry reactions are completed within about 30 sec. and the NHa is flashed off and recovered for recycle. PCB-destruction efficiencies of >99.9 have been demonstrated both in our laboratory and at Coimnodore Solutions Technologies. In these reactions all chlorine is converted to NaQ. Similar results have been achieved with CAH-contaminated soils. This is illustrated in Table 2 for soils contaminated with carbon tetrachloride, CCU- These soils were not dried and in... 

Over the last five years, U.S. ERA has supported research on a chemical dehalogenation process for destroying PCB and dioxin. Nucleophilic displacement of aromatic halides by alkali-metal polyglycoxides occurs readily at elevated temperatures. This reaction readily dechlorinates PCB in mineral oil at 100° and proceeds similarly with 1,2,3,4- TCDD in organic solvents. The addition of dipolar, aprotic solvents such as dimethyl sulfoxide increases the reaction rate and allows dechlorination reactions in dry systems at ambient conditions. Initial tests of this concept for soil decontamination at Shenandoah Stables, Missouri, failed because of high moisture content of the soil and low temperatures. The process was used successfully in the summer of 1986 to remove penta-, hexa-, hepta-, and octachlorodibenzodioxins from... 

Soil decontamination has developed from the small-scale superheated water extraction of PAHs, pesticides and polychlorinated biphenyls (PCBs). This has been carried out on a pilot scale and at 250 C almost complete soil clean-up is achieved in... 

Concern for long-term environmental damage from PCB is most often associated with former disposal and spill sites rather than concrete contamination. Since PCB contained in or on concrete is generally considered even less mobile than when contained in soils or water, PCB in concrete is not considered as great an environmental risk. PCB decontamination of concrete is therefore rarely driven by broad-based environmental concerns. 

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