Class-selective extraction of polar, moderately polar, and nonpolar organics from hydrocarbon wastes using subcritical water
- Univ. of North Dakota, Grand Forks, ND (United States)
The polarity of water drops dramatically when heated under enough pressure to maintain the liquid state. For example, the dielectric constant ({epsilon}) of water is 80 at ambient temperature, but drops to nearly 30 at 250{degree}C. Thus, low temperature water can be used to extract polar organics, while higher temperature water will extract moderately polar and nonpolar organics. Four samples (a soil, a catalyst, and two sludges) were extracted by subcritical water at different temperatures and pressures. At lower temperatures (50-150{degree}C), phenols and BTEX (benzene, toluene, ethylbenzene, and xylenes) were quantitatively extracted by liquid water, while PAHs (polycyclic aromatic hydrocarbons) and alkanes were not extracted. At 250 or 300{degree}C, liquid water effectively extracted PAHs, but the high molecular weight alkanes (e.g., > C{sub 20}) were still not extracted. The quantitative extraction of the high molecular weight alkanes was achieved only by super-heated steam (250 and 300 {degree}C at 5 atm) extractions. Class-selective extractions of phenols, alkylbenzenes, PAHs, and alkanes were achieved by simply changing water temperatures (50-300{degree}C) or pressures (5-100 atm). The recoveries of all of the target analytes achieved by subcritical water extraction compare favorably (typically 90-120%) to those of conventional organic solvent extractions. 26 refs., 2 figs., 4 tabs.
- OSTI ID:
- 460032
- Journal Information:
- Environmental Science and Technology, Vol. 31, Issue 2; Other Information: PBD: Feb 1997
- Country of Publication:
- United States
- Language:
- English
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