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

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 methanol-water (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.

Soil flushing by surfactant solution: Pilot-scale demonstration of complete technology

“…As the main condition for reaching a high enough pollutant solubilization efficacy in an aqueous solution, the necessity of an excess of critical micellar concentration of the surfactant in the leaching solution is usually mentioned [9]. Particularly, many studies related to the suitable types of surfactants and their interactions with the pollutants [3,9,[11][12][13][14][15][16], suitable composition of flushing solutions [4,[17][18][19], sorption behavior of surfactants [9,[20][21][22][23][24], biodegradability of surfactants [25,26], as well as to a processing of soil extracts with high content of both the contaminant and surfactant [27][28][29] have been published. In addition to these studies, some works describing practical technological applications of surfactants are also available [10,30].…”

Detoxification of aryl-organochlorine compounds by catalytic reduction in supercritical carbon dioxide

“…[20][21][22] Aqueous slurries of four surfactant formulations were evaluated for the mobilisation of PCB compounds from contaminated soil 23 and coupled with on line dechlorination. 24 The objectives of the current study were to evaluate mixtures of H 2 with scCO 2 for their ability to mediate the catalytic dechlorination of aromatic organochlorine compounds.…”