The pathway of dechlorination of PCB congener by a photochemical chain process in 2-propanol: the role of medium and quenching

Chemosphere
Maryam IzadifardCooper H Langford

Abstract

As part of a program aimed at developing a field process for cleanup of PCB contaminated soils using photochemistry in basic 2-propanol, additional details of the dechlorination pathway are presented. The mechanism involves a chain reaction with both homolytic photochemical C-Cl bond fission and electron transfer steps producing PCB anion radicals. Kinetics of dechlorination of various congeners show patterns of relative rates associated with the basic 2-propanol medium that are not found in other media because both electron transfer and photochemical homolysis steps determine overall rates of dechlorination and govern the pathways and relative concentrations of intermediates. The electron transfer steps display opposite structure-reactivity correlations to the photo-homolysis, C-Cl bond fission steps. Oxygen quenching is shown to differentially affect both types of steps. In contrast to the suggestion that inter system crossing can be highly efficient with reaction originating from a PCB triplet, oxygen quenching data suggest that a significant minimum of the quantum yield is non-quenchable, presumably because of a reaction path from the PCB singlet. This may help to explain why exclusion of air is not entirely necessary in pr...Continue Reading

References

Jun 12, 1974·Journal of the American Chemical Society·L O RuzoR D Schuetz
Oct 16, 1999·Chemosphere·X S MiaoX B Xu

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Citations

Aug 11, 2015·Environmental Science and Pollution Research International·Marek RoszkoRenata Jędrzejczak
Oct 7, 2016·Environmental Science. Processes & Impacts·Guangping FanDongmei Zhou
Oct 4, 2012·Journal of Environmental Science and Health. Part A, Toxic/hazardous Substances & Environmental Engineering·Jiansong KongCooper H Langford

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