Oxidation of chlorinated solvents

Chlorine cannot be stored economically or moved long distances. International movements of bulk chlorine are more or less limited to movements between Canada and the United States. In 1987, chlorine moved in the form of derivatives was 3.3 million metric tons or approximately 10% of total consumption (3). Exports of ethylene dichloride, vinyl chloride monomer, poly(vinyl chloride), propylene oxide, and chlorinated solvents comprise the majority of world chlorine movement. Countries or areas with a chlorine surplus exported in the form of derivatives include Western Europe, Bra2il, USA, Saudi Arabia, and Canada. Countries with a chlorine deficit are Taiwan, Korea, Indonesia, Vene2uela, South Africa, Thailand and Japan (3). 

In some cases, microorganisms can transform a contaminant, but they are not able to use this compound as a source of energy or carbon. This biotransformation is often called co-metabolism. In co-metabolism, the transformation of the compound is an incidental reaction catalyzed by enzymes, which are involved in the normal microbial metabolism.33 A well-known example of co-metabolism is the degradation of (TCE) by methanotrophic bacteria, a group of bacteria that use methane as their source of carbon and energy. When metabolizing methane, methanotrophs produce the enzyme methane monooxygenase, which catalyzes the oxidation of TCE and other chlorinated aliphatics under aerobic conditions.34 In addition to methane, toluene and phenol have been used as primary substrates to stimulate the aerobic co-metabolism of chlorinated solvents. 

Cometabolism refers to the degradation of the chlorinated solvent as a by-product of the degradation of other substrates by microorganisms, and does not benefit the microorganism. As the degree of dechlorination decreases, the cometabolism rates increase. Thus, less oxidized or chlorinated solvents such as chlorinated ethenes (excluding PCE) biodegrade more favorably under aerobic conditions. 

The chemical resistance is generally inferior to that of comparable polyethylenes and decreases when VA rises. EVAs are attacked by concentrated strong acids, halogens, oxidizing acids, chlorinated solvents, certain oxidants, aliphatic and aromatic hydrocarbons, alcohols, ketones, esters, and some others. 

Oxidation/epoxidation methods without the use of chlorinated solvents New greener fluorination methods... 

An in situ chemical oxidation field demonstration using potassium permanganate for the remediation of chlorinated solvents was conducted in 1996 at the U.S. Department of Energy s (DOE s) Kansas City Plant in Kansas City, Missouri. The total cost of the demonstration was approximately 1,000,000. This included all pre- and posttesting, permitting, equipment, and labor. The estimated cost of this technology is around 128/yd (D18766A, p.l5). 

The transformation of the laboratory protocol into this successful industrial process was facilitated by i) the addition of an organic base (diisopropylethyla-mine), which substantially increased both the ee and the productivity ii) the addition of the appropriate amount of water (0.5/1 with respect to Ti) which directly influenced the stereochemical outcome Hi) the use of a 1 2 ratio of [Ti(0- -Pr)4] and diethyl tartrate iv) the use of cumene hydroperoxide as the oxidant v) the replacement of chlorinated solvents with more environmentally friendly ones (toluene, ethyl acetate) and vi) carrying out the oxidation at higher and technically more convenient temperatures than before ( 0-30°C vx. -20°C). 

The photochemical oxidation of chlorinated hydrocarbons into phosgene has been the subject of particular concern for the welding workshop [679,2217]. Solvent residues from degreasing procedures may remain on the part to be welded, particularly in cracks and cavities where the solvent may have been drawn by capillary action [627]. Upon exposure to the heat of the welding arc, the residues vaporize and although some thermal oxidation will then... 

Further papers in this section report intramolecular hydrogen-bonding in 2-arylaminomethylenecycloalkanones (menthone, carvomenthone, camphor)," the effect of chlorinated solvents on the stability constants of hydrogen-bonded complexes between pyrrole and, inter alia, fenchone,and a correlation of half-wave oxidation potentials with the pK values of the corresponding conjugate acids e.g. 3-endo-cyanocamphor). ... 

Chervinskii [162] for the oxidation of chlorine-substituted p-xylene, and by Kiiko and Matkovskii [163] in the study of the effect of chlorinated solvents on the oxidation of dimethylnaphthalene. 

As mentioned above, a single chlorinated solvent plume can exhibit different types of behavior in different portions of the plume. This can be beneficial for natural biodegradation of chlorinated solvent plumes. For natural attenuation, this may be the best scenario. PCE, TCE, and DCE are reductively dechlorinated with accumulation of VC near the source area (Type 1) then, VC is oxidized (Type 3) to carbon dioxide, either aerobically or via Fe(III) reduction further downgradient and does not accumulate. Vinyl chloride is removed from the system much faster under diese conditions than under reducing conditions. 

Free chlorine and bromine cause oxidation of the solvent, but iodine is soluble possibly with slight electrolytic dissociation ... 

The reductive dehalogenation of chlorinated solvents in the presence of iron is believed to be a charge-transfer process, which also involves oxidation of the iron and dissociation of water. In the subsurface, where no oxygen is present, the reaction is believed to be driven by the iron corrosion reaction. However, the mechanism for this process is not yet known. In fact, it is safe to say that development of the emplacement and design technology for reactive iron barriers has rapidly outpaced the development of a satisfactory theory for the reaction process. 

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