Carbon tetrachloride degradation compound

The reaction proceeds until each chlorine ion is removed. For example, carbon tetrachloride would be reduced to chloroform, then to methylene chloride, and finally to methane (the reduction of methylene chloride takes several months, however). No degradation products other than the parent compounds were found therefore, degradation is simple, reductive dechlorination, with the zero-valent iron serving as an electron donor. The reaction was pseudo first-order and the reaction constant, k, decreased with each additional dehalogenation step (Gillham and O Hannesin, 1994). 

The highest yield of degradation products (HDBP, H2MBP, phosphoric acid, carbonyl compounds) occurred in the TBP-CC14-HN03 system (87). As a result, it has been suggested that the considerable amounts of hydrochloric acid produced could accelerate the process of degradation. On the other hand, the use of carbon tetrachloride as diluent resulted in a very low yield of nitro compounds. An important sensitization effect was also reported by Nash with tetrachloroethylene G(-TBP) = 3.8 0.6 and 9.2 3 for pure molecule and TCE solution (41). 

Lipczynska-Kochany E, Harms S, Milburn R, Sprah G, Nadarajah N. Degradation of carbon tetrachloride in the presence of iron and sulphur containing compounds. Chemosphere 1994 29 1477-1489. 

Tubular reactor containing packed bed was used in a noncirculating mode to study the photocatalytic degradation of TCE and tetra-chloroethylene (Yamazaki-Nishida et al., 1996). The packed bed contained titanium dioxide pellets (1 mm in diameter), prepared by sol-gel and fired at 200-500°C. An inverse correlation between the firing temperature of the pellets and the formation of undesirable chlorinated compounds such as chloroform and carbon tetrachloride was foimd. 

Researchers have discovered that the bacterium Sheu/anella oneidensis is capable of degrading carbon tetrachloride, suggesting a possible simple and safe way to clean up areas contaminated with the compound. 

To manufacture chlorinated rubber (CR) natural or synthetic rubber such as polyethylene, polypropylene or polyisoprene is degraded to low molecular mass compounds by mastication or addition of radical formers and dissolved in carbon tetrachloride (CTC). Chlorine contents are typically 64-68 wt%. Chlorine gas is introduced into this solution and reacts with the raw material to form CR. The solution is then introduced into boiling water. The CR is precipitated, and the solvent vaporizes. The CR is separated from water, rinsed, dried and ground to form a white powder which is the saleable product. After removal of the water, chlorine, hydrochloric acid and other impurities the solvent is reused. 

Figure 23.2.2. Anaerobic degradation of carbon tetrachloride. An example of anaerobic dehalogenation, using carbon tetrachloride as the model compound. In many cases, these reactions occur under cometabolic conditions meaning that an alternative growth substrate must be present to serve as an electron donor to drive the reduction reactions whereby carbon tetrachloride is used as the electron acceptor. Three known pathways for microbial degradation of carbon tetrachloride have been identified [U.E. Krone, R.K. Thauer, H.P. Hogenkamp, and K. Steinbach, Biochemistry, 3d 0), 2713 (1991) C.H. Lee, T.A. Lewis, A. Paszczynski, andR.L. Crawford Biochem Biophys Res Commun, 261(3), 562 (1999)]. These pathways are not enzymatically driven but rely on corrinoid and corrinoid-like molecules to catalyze these reactions.

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