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Dechlorination kinetics of monochlorobiphenyls by Fe/Pd: Effects of solvent, temperature, and PCB concentration

Well-known, yet undefined, changes in the conditions and activity of palladized zerovalent iron (Fe/Pd) over an extended period of time hindered a careful study of dechlorination kinetics in long-term experiments. A short-term experimental method was, therefore, developed to study the effects of tem...

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Published in:Applied catalysis. B, Environmental Environmental, 2008-02, Vol.78 (3-4), p.371-380
Main Authors: Fang, Yuanxiang, Al-Abed, Souhail R.
Format: Article
Language:English
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Summary:Well-known, yet undefined, changes in the conditions and activity of palladized zerovalent iron (Fe/Pd) over an extended period of time hindered a careful study of dechlorination kinetics in long-term experiments. A short-term experimental method was, therefore, developed to study the effects of temperature and solvent on the dechlorination of monochlorobiphenyls (MCBs), 2-chlorobiphenyl (2-ClBP), in particular by Fe/Pd. The experiments started with specified initial conditions and lasted only for 10min. The average value (k) of the first-order rate constant for the dechlorination of 2-ClBP was 0.13±0.03Lm−2h−1, not significantly different from the average values for 3-chlorobiphenyl and 4-chlorobiphenyl. The apparent activation energy was 20±4kJmol−1 and 17±7kJmol−1, in a temperature range between 4°C and 60°C, for the dechlorination of 2-ClBP using two batches of Fe/Pd catalyst. The k values decreased significantly in mixtures with a methanol concentration higher than 10%. The values of the rate constant were slightly influenced by the initial concentrations in the experiments at a low temperature and in a solution with a high methanol concentration. The concentration dependence was described with a Langmuir equation, based on the Langmuir–Hinshelwood mechanism that includes an adsorption step of a single species preceding a rate-determining catalytic reaction.
ISSN:0926-3373
1873-3883
DOI:10.1016/j.apcatb.2007.09.009