Trichloroethylene, reduction

Deng B., Hu S, and Burris D. R. (1998) Effect of iron corrosion inhibitors on trichloroethylene reduction. In Physical, Chemical, and Thermal Technologies (ed. G. B. Wickramanayake and R. R. Hinchee), pp. 341-346. Battelle Press. 

Su C. and Puls R. W. (1999) Kinetics of trichloroethylene reduction by zerovalent iron and tin pretreatment effect, apparent activation energy, and intermediate products. 

Exposure occurs almost exclusively by vapor inhalation, which is followed by rapid absorption into the bloodstream. At concentrations of 150—186 ppm, 51—70% of the trichloroethylene inhaled is absorbed. MetaboHc breakdown occurs by oxidation to chloral hydrate [302-17-OJ, followed by reduction to trichloroethanol [115-20-8] part of which is further oxidized to trichloroacetic acid [76-03-9] (35—37). Absorbed trichloroethylene that is not metabolized is eventually eliminated through the lungs (38). The OSHA permissible exposure limit (PEL) eight-hour TWA concentration has been set at 50 ppm for eight-hour exposure (33). 

Groundwater Industrial contamination of ground water reserves Reduction of total organic halogens (TOX) and adsorbable organic halogens (AOX) including chloroform, tetrachloroethylene, and trichloroethylene... 

The antiparasitic drug clorsulon (206), contains a rather unusual trichloroethylene group. This function is established early in the syntliesis by treatment of the perhalogenated compound 203 obtained from reduction of 202 with iron powder. Chlorosulfonation of 204 by means of chloro-sulfonic acid, followed by conver.sion of. sulfonyl chloride 205 to the amide, gives clorsulon (206) 153],... 

Degradation of trichloroethylene by anaerobes via reductive dehalogenation can be problematic because a common product is vinyl chloride, a known carcinogen (Ensley 1991). In an anaerobic colunm operated under methanogenic conditions, 100% transformation of injected tetrachloroethylene and trichloroethylene to... 

Alvarez-Cohen L, McCarty PL. 1991a. Effects of toxicity, aeration and reductant supply on trichloroethylene transformation by a mixed methanotrophic culture. Appl Environ Microbiol 57 228-235. 

Freedman DL, Gossett JM. 1989. Biological reductive dechlorination of tetrachloroethylene and trichloroethylene to ethylene under methanogenic conditions. Appl Environ Microbiol 55 2144-2151. 

Jaspers RM, Muijser H, Lammers JH, et al. 1993. Mid-frequency hearing loss and reduction of acoustic startle responding in rats following trichloroethylene exposure. Neurotoxicol Teratol 15 407-412. 

Goltz MN, RK gandhi, SM Gorelick, GD Hopkins, LH Smith, BH Timmins, PL McCarthy (2005) Field evaluation of in situ source reduction of trichloroethylene in groundwater using bioenhanced in-situ vapor stripping. Environ Sci Technol 39 8963-8970. 

Isotope fractionation between the vapor phase and the dissolved aqueous phase has been studied only for toluene and trichloroethylene (carbon only [545, 690]). Fractionation associated with adsorption has been quantified only for toluene in regard to sample extraction using a poly(dimethylsilo-xane)-coated solid-phase microextraction fiber [373] and qualified for benzene, toluene, and ethylbenzene based on high-pressure liquid chromatography analyses of isotopically labeled and unlabeled compounds (carbon and hydrogen [692]). Isotope fractionation associated with the reductive dechlorination of chlorinated ethylenes by zero-valent iron and zinc has been... 

In anoxic hypolimnion samples collected from Lower Mystic Lake, MA, hexachloroethane was abiotically transformed into tetrachloroethylene via reductive elimination and to pentachloro-ethane via hydrogenolysis. Tetrachloroethylene accounted for 70% of hexachloroethane in unaltered lake water and 62% in filter-sterilized water after 10 d. Trichloroethylene and pent-achloroethane accounted for <1 and 2% in unaltered lake water and filter-sterilized water, respectively. Disappearance rate constants for hexachloroethane were 0.33/d for unaltered water and 0.26/d for filter-sterilized water. At least 80% of the hexachloroethane disappearance in unaltered water was abiotic in origin due to the reactions with naturally occurring aqueous polysulfides, H2S and (Miller et al, 1998a). 

Butler and Heyes (1998) investigated the reductive dechlorination of hexachloroethane in water by iron sulfide. Tetrachloroethylene was the major product with pentachloroethane as a minor intermediate. Final reaction products were trichloroethylene, c/s-1,2-dichloroethylene, and acetylene. The rate of reaction increased with increasing iron sulfide concentrations and pH. At pH 7.8, first-order rate constants were 0.0726, 0.086, and 0.533/h at iron sulfide concentrations of 10, 25, and 100 g/L, respectively. At an iron sulfide concentration of 100 g/L, first-order rate... 

Source Vinyl chloride in soil and/or groundwater may form from the biotransformation of 1,1,1-trichloroethane (Lesage et al, 1990), trichloroethylene, 1,2-dichloroethylene (Smith and Dragun, 1984 Wilson et al, 1986), and from the chemical reduction of trichloroethylene by zero-valent iron (Orth and Gillham, 1996). 

In animal studies acetone has been found to potentiate the toxicity of other solvents by altering their metabolism through induction of microsomal enzymes, particularly cytochrome P-450. Reported effects include enhancement of the ethanol-induced loss of righting reflex in mice by reduction of the elimination rate of ethanol increased hepatotoxicity of compounds such as carbon tetrachloride and trichloroethylene in the rat potentiation of acrylonitrile toxicity by altering the rate at which it is metabolized to cyanide and potentiation of the neurotoxicity of -hexane by altering the toxicokinetics of its 2,4-hexane-dione metabolite.Because occupationally exposed workers are most often exposed to a mixmre of solvents, use of the rule of additivity may underestimate the effect of combined exposures. ... 

Whereas Cgg and C g are easy to reduce, their oxidation occius at comparatively high anodic potentials [1, 2]. Theoretical investigations predict the first oxidation potential ofCgg to be comparable to that of naphthalene [3]. Anodic electrochemistry with fuUerenes has been carried out with Cgg films [4] as well as in solution [5-7]. Cyclic voltammetry of Cgg in a 0.1 M solution of Bu4NPFg in trichloroethylene (TCE) at room temperatare exhibits a chemically reversible, one-electron oxidation wave at -tl.26 V vs Fc/Fc (Figiue 8.1) [7]. Under identical conditions, a one-electron, chemically reversible oxidation is also observed for Cyg. The oxidation of Cyg occurs 60 mV more negative than that of Cgg at -tl.20 V vs Fc/Fc. The energy difference between the first oxidation and the first reduction potential is a measiue of the... 

Largely, the same principles apply for water treatment. Consequently, activated carbon is suitable for organic molecules that are nonpolar and of high molecular weight. Trichloroethylene, benzene, ethylbenzene, toluene, and xylene are easily adsorbed in the gas phase when activated carbon, for instance, is used. On the other hand, adsorption is not preferably selected in applications in relation to aldehydes, ketones, and alcohols. In a successful application, reduction in emissions from 400-2000 ppm to under 50 ppm can be achieved (EPA, 1999), especially for VOCs with boiling points between 20 -and 175 °C. 

Such high photocatalytic reactivities of photo-formed e and h can be expected to induce various catalytic reactions to remove toxic compounds and can actually be applied for the reduction or elimination of polluted compounds in air such as NO cigarette smoke, as well as volatile compounds arising from various construction materials, oxidizing them into CO2. In water, such toxins as chloroalkenes, specifically trichloroethylene and tetrachloroethene, as well as dioxins can be completely degraded into CO2 and H2O. Such highly photocatalyti-... 

Trichloroethylene (TCE) and perchloroethylene (PCE) require cleavage of the carbon-halogen bonds. Two methods of cleavage are P-elimination by dehy-drohalogenation, as shown in Equation (13.14), and nucleophilic substitution by either water or hydrogenolysis in Equation (13.15). The proposed pathways for reduction of chloroethylenes by zero-valent iron are as follows ... 

Campbell, T.J., Burris, D.R., Roberts, A.L., and Wells, J.R., Trichloroethylene and tetrachloroethylene reduction in a metallic iron-water-vapor batch system, Environ. Toxicol. Chem., 16(4), 625-630, 1997. 

Burris, D.R., C.A. Delcomyn, M.H. Smith, and A.L. Roberts. 1996. Reductive dechlorination of tetrachloroethylene and trichloroethylene catalyzed by vitamin B12 in homogeneous and heterogeneous systems. Environ. Sci. Technol. 30, 3047-3052. 

Figure I. Reduction of trichloroethylene on ZVI surfaces through hydrogenolysis and reductive elimination pathways (adapted from Roberts et al., 1996).

A single site model assumes only one type of surface sites, i.e., the same type of sites is responsible for trichloroethylene adsorption and reduction. The kinetic model developed herein is based on the following reaction... 

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