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CLEANING UP PESTICIDE CONTAMINATED SOILS: COMPARING EFFECTIVENESS OF SUPERCRITICAL FLUID EXTRACTION WITH SOLVENT EXTRACTION AND LOW TEMPERATURE THERMAL DESORPTION
Citation:
SahleDemessie**, E AND T Richardson*. CLEANING UP PESTICIDE CONTAMINATED SOILS: COMPARING EFFECTIVENESS OF SUPERCRITICAL FLUID EXTRACTION WITH SOLVENT EXTRACTION AND LOW TEMPERATURE THERMAL DESORPTION. JOURNAL OF ENVIRONMENTAL TECHNOLOGY 21(4):447-456, (2000).
Description:
Bench-scale supercritical fluid extraction (SFE) studies were performed on soil samples obtained from a Superfund site that is 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-minute extraction at 30 MPa and 80NC 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 96 to 98% of the four contaminants removed, except for DDE which existed at low initial concentrations. The contaminated volume reduction was 40 to 50 times. Low temperature thermal desorption employed at 350NC for 30 minutes removed more than 98% for each contaminant except DDE. However, solvent extraction includes costly solvent regeneration and recycling steps, and thermal desorption generates air pollutants that require an expensive particulate removal and gas stream cleaning. This study attempted to show 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.