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ARS Home » Research » Publications at this Location » Publication #72590


item Sahle Demessie, Endalkachew

Submitted to: American Institute of Chemical Engineers Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/10/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Bench-scale supercritical fluid extraction studies were performed on soil samples obtained from a Superfund site contaminated with high levels of p,p'-DDT, p,p'-DDD, p,p'-DDE, toxaphene and hexachlorocyclohexane. The effectiveness of supercritical fluid extraction was assessed using carbon dioxide as a solvent over a wide range of conditions. A 30 minutes extraction at 30 Mpa and 80 deg C was able to remove more than 98% of the contaminants and reduce the contaminated volume by a factor of 500. A mathematical model was developed to explain the rate mechanism of the extraction process. The performance of the supercritical extraction was compared to that of solvent extraction and thermal desorption performed on the same soil. A six-stage solvent extraction using methanol or iso-propanol achieved 99% contaminants removal and a volume reduction of 40 to 50 times. Thermal desorption employed at 350 deg C for 30 minutes removed 99.0% of the contaminants. However, solvent extraction includes a costly solvent regeneration and recycling steps, and thermal desorption may involve an expensive particulate removal and gas stream cleaning.