Supercritical CO sub 2 -cosolvent extraction of contaminated soils and sediments

Journal Article · Thu Nov 01 04:00:00 EST 1990 · Environmental Progress; (USA)

DOI:https://doi.org/10.1002/ep.670090412· OSTI ID:5608175

Dooley, K M; Ghonasgi, D; Knopf, F C ^[1]

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1. Louisiana State Univ., Baton Rouge (USA)

DDT- or PCB-contaminated topsoils of high organic content were extracted using supercritical CO{sub 2} or CO{sub 2}-5 wt% cosolvent (toluene, acetone, methanol, acetic acid, diethylamine) mixtures at 313 K and 101 bar. In separate experiments, the pure contaminants were dissolved in supercritical CO{sub 2} at the same conditions and the equilibrium solubilities determined. Most of the cosolvents only marginally improve extraction rates over the case of pure CO{sub 2}. Methanol, however, increases total amounts of DDT removal from 50-80% to > 95%, and increases DDT and PCB extraction rates by as much as an order of magnitude. Methanol is a superior cosolvent probably because its hydrogen-bonding ability is better suited to interaction with the organic matter in the soil (humic acids, fulvic acids, polysaccharides); the organic matter essentially dissolves the contaminants in the soil matrix. Comparing a simple fixed-bed, local equilibrium (based on pure contaminant equilibria) desorption model to the actual desorption data indicates that contaminant solubilities in supercritical fluids are enhanced (over the pure contaminant case) when desorbing from soils. The enhancements may be related to the simultaneous desorption of other low molecular-weight organics from the soils.

• OSTI ID: 5608175
• Journal Information: Environmental Progress; (USA), Journal Name: Environmental Progress; (USA) Vol. 9:4; ISSN ENVPD; ISSN 0278-4491
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
ALCOHOLS
AROMATICS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHLORINATED AROMATIC HYDROCARBONS
CLEANING
DDT
DECONTAMINATION
FLUID FLOW
HALOGENATED AROMATIC HYDROCARBONS
HYDROXY COMPOUNDS
INSECTICIDES
METHANOL
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PESTICIDES
SEDIMENTS
SOILS
SOLVENTS
TURBULENT FLOW