Dechlorination of polychlorinated

Yak HK, BW Wenclawiak, IE Cheng, JG Doyle, CM Wai (1999) Rednetive dechlorination of polychlorinated biphenyls by zerovalent iron in snbcritical water. Environ Sci Technol 33 1307-1310. 

There has been snbstantial interest in the complete dechlorination of chloroethene to ethene, since chloroethene is an nndesirable prodnct of partial dechlorination of polychlorinated ethenes. Strains of Dehalococcoides sp., and especially D. ethenogenes that is possibly unique in being able to carry out the dechlorination of tetrachloroethene to chloroethene and ethene (Magnuson et al. 2000 Maymd-Gatell et al. 1999), have attracted particnlar attention ... 

Attention has been directed to the dechlorination of polychlorinated benzenes by strains that use them as an energy source by dehalorespiration. Investigations using Dahalococcoides sp. strain CBDBl have shown its ability to dechlorinate congeners with three or more chlorine substituents (Holscher et al. 2003). Although there are minor pathways, the major one for hexachlorobenzene was successive reductive dechlorination to pentachlorobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4-trichlorobenzene, and 1,4-dichlorobenzene (Jayachandran et al. 2003). The electron transport system has been examined by the use of specific inhibitors. lonophores had no effect on dechlorination, whereas the ATP-synthase inhibitor A,A -dicyclohexylcarbodiimide (DCCD) was strongly inhibitory (Jayachandran et al. 2004). 

Bedard DL, JE Quensen III (1995) Microbial reductive dechlorination of polychlorinated biphenyls. In Microbial transformation and Degradation of Toxic Organic Chemicals (Eds LY Yonng, CE Cemiglia), pp. 127-216. Wiley-Liss, New York. 

Wu Q, JEM Watts, KR Sowers, HD May (2002) Identification of a bacterium that specifically catalyzes the reductive dechlorination of polychlorinated biphenyls with doubly flanked chlorines. Appl Environ Microbiol 68 807-812. 

Drenzer NJ, T1 Eglinton, CO Wirsen, HD May, Q Wu, KR Sowers, CM Reddy (2001) The absence and application of stable carbon isotope fractionation during the reductive dechlorination of polychlorinated biphenyls. Environ Sci Technol 35 3310-3313. 

Barkovskii, A.L. and P. Adriaens. 1998. Impact of humic constituents on microbial dechlorination of polychlorinated dioxins. Environ. Toxicol. Chem. 17 1013-1020. 

The reactions include an unusual Diels-Alder reaction and a very useful synthetic method, the dechlorination of polychlorinated compounds. At the present time this procedure is the best one available for the removal of chlorine from an organic molecule. The end product, 7,7-dimethoxybicyclo[2.2.1]heptene, is an interesting and useful intermediate in bicyclic chemistry it has a reactive double bond and a protected carbonyl group in the 7-position. 

In activated sludge, 80.6% degraded after a 47-h time period (Pal et al., 1980). Chemical/Physical. Zhang and Rusling (1993) evaluated the bicontinuous microemulsion of surfactant/oil/water as a medium for the dechlorination of polychlorinated biphenyls by electrochemical catalytic reduction. The microemulsion (20 mL) contained didodecyldi-methylammonium bromide, dodecane, and water at 21, 57, and 22 wt %, respectively. The catalyst used was zinc phthalocyanine (2.5 nM). When PCB-1221 (72 mg), the emulsion and catalyst were subjected to a current of mA/cm on 11.2 cm lead electrode for 10 h, a dechlorination yield of 99% was achieved. Reaction products included a monochlorobiphenyl (0.9 mg), biphenyl, and reduced alkylbenzene derivatives. 

Zhang, S. and Rusling, J.F. Dechlorination of polychlorinated biphenyls by electrochemical catalysis in a biocontinuous microemulsion. Environ. Sci. Technol, 27(7) 1375-1380, 1993. 

Anaerobic bioreactors have been used since the 1880s to treat wastewaters with large amounts of suspended solids. However, anaerobic reactors are sensitive to toxic pollutants and vulnerable to process upsets, and have been used mainly for municipal sludge digestion. For methane production the sequential metabolism of the anaerobic consortia must be balanced, and the methanogens in particular are vulnerable to process upsets. Recently, anaerobic-aerobic processes (Figure 1.1) have been developed for the mineralization of xenobiotics. These processes take advantage of an anaerobic reactor for the initial reductive dechlorination of polychlorinated compounds or the reduction of nitro substituents to amino substituents. If the reduced compounds are more readily mineralized in an aerobic reactor, an anaerobic-aerobic process is feasible. 

Alder, A. C., Haggblom, M. M., Oppenheimer, S. R. Young, L. Y. (1993). Reductive dechlorination of polychlorinated biphenyls in anaerobic sediments. Environmental Science Technology, 27, 530-8. 

Quensen, J.F. Ill, Tiedje, J.M. Boyd, S. A. (1988). Reductive dechlorination of polychlorinated biphenyls by anaerobic microorganisms from sediments. Science, 242, 752-4. 

Rhee, G-Y., Sokol, R. C., Bethoney, C. M. Bush, B. (1993b). Dechlorination of polychlorinated biphenyls by Hudson River sediment organisms Specificity to the chlorination pattern of congeners. Environmental Science Technology, 27, 1190—2. 

Van Dort, H. Bedard, D. L. (1991)- Reductive ortho and meta dechlorination of polychlorinated biphenyl congeners by anaerobic microorganisms. Applied and Environmental Microbiology, 57, 1576-8. 

Chuang, F., Larson, R.A., and Wessman, M.S., Zero-valent iron-promoted dechlorination of polychlorinated biphenyls, Environ. Sci. Technol., 29, 2460-2463, 1995. 

Grittini, C., Malcomson, M., Fernando, Q., and Korte, N., Rapid dechlorination of polychlorinated biphenyls on surface of a Pd/Fe bimetallic system, Environ. Sci. Technol, 29(11), 2898-2900, 1995. 

Wu QX, Majid A, Marshall WD. Reductive dechlorination of polychlorinated biphenyl compounds in supercritical carbon dioxide. Green Chem 2000 2 127-132. 

Hammel KE, Tardone PJ. The oxidative 4-dechlorination of polychlorinated phenols is catalyzed by extracellular fungal lignin peroxidases. Biochemistry 1988 27 6563-6568. 

Kluyev, N., Cheleptchikov, A., Brodsky, E., Soyfer, V. and Zhilnikov, V. (2002) Reductive dechlorination of polychlorinated dibenzo-p-dioxins by zerovalent iron in subcritical water. Chemosphere 46,1191-1193. 

Bedard, D.L. Quensen J.F. ni. Microbial Reductive Dechlorination of Polychlorinated Biphenyls In Microbial Transformation and Degradation of Toxic Organic Chemicals, L.Y. Young C.E. Cerniglia, editors, Wiley-Liss New York, 1995, p. 127-216. 

The bulk of the toxaphene components detected in environmental samples are polychlorinated bornanes and a few camphenes or bornenes. Since reductive dechlorination of polychlorinated bornanes leads to bornanes with one less chlorine atom, at present it is not possible to distinguish unequivocally between components originating from technical toxaphene and dechlorinated metabolites. This question can only be solved with fate studies of single components in the laboratory [122,165],... 

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