Abiotic and biotic reductive dehalogenation of halogenated methanes
Reductive dehalogenation is an important reaction that generally leads to detoxification of many halogenated methanes. Halogenated methanes are widely used in industrial and commercial applications and the inadvertent or deliberate release of these chemicals has caused contamination of the atmosphere, soil and groundwater. The research presented here details the study of several systems for reductive dehalogenation of chlorinated methanes. The first system described in this dissertation involves reductive dechlorination of chlorinated methanes by laboratory cultures of methanogens. A vessel was constructed that allowed maintenance of anaerobic conditions and minimized losses of the volatile chlorocarbons. Methylene chloride was not dechlorinated in the presence of pure cultures of methanogens. Similarly, dechlorination did not occur in enrichments made with samples from several different anaerobic digesters. Abiotic dehalogenation studies showed that cobalamins, cobalt-centered macrocyclic compounds, catalyzed the reductive dechlorination of several halomethanes in anaerobic, closed batch systems. These studies focused on immobilization of cobalamins to several types of supports for use in pollution remediation strategies. Cyanocobalamin bound to Epoxy-Activated Sepharose 6B and talc catalyzed the rapid reduction of carbon tetrachloride and methylene chloride to sequentially reduced products. Corroding iron metal was also studied as a reductant for halogenated methanes. Several chlorinated methanes were reductively dechlorinated in closed, anaerobic, laboratory-scale model systems containing granular iron. Carbon tetrachloride was sequentially dehalogenated, via chloroform, to methylene chloride. The initial rate of each reaction was pseudo-first order in substrate and declined substantially with each dehalogenation step. Trichloroethene was also dechlorinated by iron, although more slowly than carbon tetrachloride.
- Research Organization:
- Oregon Graduate Inst. of Science and Technology, Beaverton, OR (United States)
- OSTI ID:
- 6530462
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
ALKANES
ANAEROBIC CONDITIONS
BACTERIA
CARBON TETRACHLORIDE
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
CLEANING
COBALT
DECHLORINATION
DECONTAMINATION
DEHALOGENATION
ELEMENTS
FEASIBILITY STUDIES
GROUND WATER
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROCARBONS
HYDROGEN COMPOUNDS
IRON
METALS
METHANE
METHANOGENIC BACTERIA
METHYLENE CHLORIDE
MICROORGANISMS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXYGEN COMPOUNDS
REMEDIAL ACTION
TRANSITION ELEMENTS
WATER