Submitted to: American Institute of Chemical Engineers Annual Meeting
Publication Type: Proceedings
Publication Acceptance Date: 11/10/1996
Publication Date: N/A
Technical Abstract: Bench-scale supercritical fluid extraction (SFE) studies were performed on soil samples obtained from a Superfund site that was 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 pure and modified CO2 as a solvent over a wide range of conditions. A 30 min 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. Solvent extraction and thermal desorption treatability studies were conducted on soil samples obtained from the same site to compare their performance with that of supercritical fluid extraction. A six-stage solvent extraction using methanol or iso-propanol achieved 98% of the contaminants removed and a volume reduction of 40 to 50 times. Thermal desorption employed at 350 deg C for 30 min removed 99.9% of the contaminants. However, solvent extraction includes a costly solvent regeneration and recycling steps, and thermal desorption generates air pollutants that require an expensive particulate removal and gas stream cleaning. This study proved that SFE can be as effective as other emerging technologies in removing contaminants from soils and can reduce the contaminated volume by a large factor with low risk of air pollution.