Oxidation of Aroclor 1248 in supercritical water: A global kinetic study
Supercritical water oxidation of extracted contaminants is the second step of a two-stage supercritical fluid technology proposed to remediate soils and sediments contaminated with polychlorinated biphenyls (PCBs) and/or polyaromatic hydrocarbons. In connection with the second step, the supercritical water oxidation rate of Aroclor 1248 (A1248), a mixture of {approximately}76 PCB congeners, is investigated at 25.3 MPa and temperatures of 723, 748, 773, and 823 K. The reactions are conducted in an isothermal, isobaric plug-flow tubular reactor, and GC/ECD, GC/FID, GC/TCD, and GC/MS chromatographic methods are employed for product analysis. Experiments are conducted at a nominal A1248 feed concentration of 5.75 x 10{sup {minus}5} mol/L (reaction conditions) using a methanol solution of 5.245 g/L (5,245 ppm) and H{sub 2}O{sub 2} as an initial oxidant (providing {approximately}20 mol +ACU- excess of O{sub 2}). Molar global conversion of A1248 varies from 36.06% (for residence time equal to 6.29 s at 723 K) to 99.95% (54.4 s at 823 K). The overall conversion follows apparent second order, and the rate constant calculated from the data leads to Arrhenius parameters of frequency factor A = 10{sup 17.0{+-}0.1} s{sup {minus}1} (mol/L){sup {minus}1} and energy of activation E{sub a} = 186 {+-} 2 kJ/mol (44.43 {+-} 0.51 kcal/mol). The congener specific analysis indicates a buildup of intermediate congener byproducts, which also undergo oxidation decomposition. The identified reaction products are mainly biphenyl, low-chlorinated PCB congeners such as 2-chlorobiphenyl and 2,2{prime}-dichlorobiphenyl, CO, and CO{sub 2}.
- Research Organization:
- Syracuse Univ., NY (US)
- OSTI ID:
- 20019037
- Journal Information:
- Industrial and Engineering Chemistry Research, Vol. 39, Issue 3; Other Information: PBD: Mar 2000; ISSN 0888-5885
- Country of Publication:
- United States
- Language:
- English
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