Halogenated aliphatic contaminants

Grosjean D (1991) Atmospheric chemistry of toxic contaminants. 4. Saturated halogenated aliphatics methyl bromide, epichlorhydrin, phosgene. J Air Waste Manage Assoc 41 56-61. 

Sonier DN, NLDuran, GB Smith (1994) Dechlorination of trichlorofluoromethane (CFC-11) by sulfate-reducing bacteria from an aquifer contaminated with halogenated aliphatic compounds. Appl Environ Microbiol 60 4567-4572. 

Bimetallic nanomaterials such as Pd/Fe, Ni/Fe, and Pd/Au are also active catalysts for the degradation of organic contaminants, including halogenated pesticides, nitroaromatics, polychlorinated biphenyls, and halogenated aliphatics (ethenes and methanes) [151]. 

Grosjean, D., Atmospheric Chemistry of Toxic Contaminants. 4. Saturated Halogenated Aliphatics Methyl Bromide, Epichlorhy-drin, Phosgene, J. Air Waste Manage. Assoc., 41, 56-61 (1991b). 

Organic chemicals that are susceptible to oxidation and are of concern from the perspective of contamination and environmental degradation include aliphatic and aromatic hydrocarbons, alcohols, aldehydes, and ketones phenols, polyphenols, and hydroquinones sulfides (thiols) and sulfoxides nitriles, amines, and diamines nitrogen and sulfur heterocyclic compounds mono- and di-halogenated aliphatics linear alkybenzene-sulfonate and nonylphenol polyethoxylate surfactants and thiophosphate esters. Table... 

Bouwer EJ, Wright JP. 1988. Transformations of trace halogenated aliphatics in anoxic biofilm columns. Journal of Contaminant Hydrology 2 155-169. 

S Halogenated Compounds Many halogenated compounds, either because of their extensive use or their persistence are of environmental interest. The smaller, halogenated aliphatics have been used extensively and are common ground water contaminants," while the persistence of the PCBs and chlorinated dibenzo dioxins is well documented. Hydroxyl radicals are the more important oxidants in the vapor phase and the hydrocarbon structure determines the nature of the reaction. Second-order rate constants for some of these compounds are summarized in Table 6.27. 

Reductions Microbial and mammalian nitroreductase reduces nitro compounds to amines. Chlorinated alkanes and alkenes are common contaminants in ground water and chlorinated aromatics, PCBs, organochlorine pesticides, are often detected in soils and sediments and it has been of interest to evaluate the potential for these compounds to be metabolized. A number of microorganisms are able to dechlorinate both halogenated aliphatic and aromatic compounds in a reduction reaction." It has been observed that the more highly chlorinated congeners are more reactive in these systems in contrast to the response in oxidative dechlorinations. 

The widespread contamination of surface and groundwaters by halogenated aliphatics has prompted efforts to determine pathways for the degradation of these environmental pollutants. Hydrolysis half-lives for halogenated aliphatics range from months to years however, because residence times for these pollutants in groundwater systems are often measured in years, hydrolysis will be an environmentally significant transformation pathway for these compounds. 

Pathway considerations are as important as kinetic considerations in assessing the prospects for detoxification of halogenated aliphatics. In the following sections, we summarize recent literature on the anaerobic and aerobic degradation of the most significant halogenated C-1 and C-2 contaminants. 

The use of commercially available zero-vale 12nt-metal powders for the degradation of halogenated aliphatics is well documented (4). Nanoscale Fe° has a much smaller grain size than commercially available powdered iron, making it much more reactive. Nanoiron and nanoscale bimetallic particles have been shown to be extremely effective for the reductive dehalogenation of common soil and ground water contaminants such as chlorinated methanes (5), chlorinated ethanes (5) and chlorinated ethenes (7, 8) and essentially eliminate all the undesirable byproducts (P). 

Low reactivity contaminants halogenated hydrocarbons, saturated aliphatics, benzene. 

Such xenobiotics as aliphatic hydrocarbons and derivatives, chlorinated ahphatic compounds (methyl, ethyl, methylene, and ethylene chlorides), aromatic hydrocarbons and derivatives (benzene, toluene, phthalate, ethylbenzene, xylenes, and phenol), polycyclic aromatic hydrocarbons, halogenated aromatic compounds (chlorophenols, polychlorinated biphenyls, dioxins and relatives, DDT and relatives), AZO dyes, compounds with nitrogroups (explosive-contaminated waste and herbicides), and organophosphate wastes can be treated effectively by aerobic microorganisms. 

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