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Issue 5, 2001
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Abstract

Polychlorinated biphenyl (PCB) formulation (Aroclor 1242 or 1248)–surfactant (Brij 97 or Triton CF54) emulsions (0.1–1.0%, v/v) were extracted with supercritical carbon dioxide (scCO2). The declinations curve that resulted for each loading of PCB substrate was accurately modelled as a single-exponential decay, and the half-life [t1/2, 10.76 min ± 2% (Brij 97) or 10.0 min ± 14% (Triton CF54)] was independent of the level of loading. When the extraction was combined with on-line dechlorination, t1/2 was increased to 17.62 min ± 6% or 16.46 min ± 5%, respectively The dechlorination reactor contributed appreciably to the back-pressure of the system so that, under identical scCO2 head pressures, the flow rate at the exit of the system was reduced from 1500 mL min−1 (as decompressed gas) to 900 mL min−1. When corrected for the difference in flow rates, the declination curves in the absence and presence of the reactor became virtually identical. For a surfactant suspension from a soil that was field-burdened with only 6 ppm PCBs, extended operation (extraction–dechlorination) for 15 h, during which the substrate suspension was replaced every 30 min, caused no loss of the dechlorination efficiency; however, for 1% (v/v) Aroclor 1242 or 1248 in surfactant suspension, the reactor gradually lost reactivity over 5 h of continued operation. However, the reactivity could be restored virtually completely by purging the reactor column with scCO2 for 3 h or washing the column at ambient temperature with 30 mL of methanolwater (7 + 3, v/v). Mass spectrometry of the reaction products indicated that the principal products included biphenyl and toluene, but methylated benzenes and phenols were also present.

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Article information


Submitted
11 Jun 2001
Accepted
17 Jul 2001
First published
12 Sep 2001

J. Environ. Monit., 2001,3, 499-504
Article type
Paper

Extractions of polychlorinated biphenyl (PCB) compounds from surfactant suspension/soil extracts with dechlorination on-line

Q. Wu and W. D. Marshall, J. Environ. Monit., 2001, 3, 499
DOI: 10.1039/B105114H

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