Volatile tetrachloroethylene

AH volatile organic solvents are toxic to some degree. Excessive vapor inhalation of the volatile chloriaated solveats, and the central nervous system depression that results, is the greatest hazard for iadustrial use of these solvents. Proper protective equipment and operating procedures permit safe use of solvents such as methylene chloride, 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene ia both cold and hot metal-cleaning operations. The toxicity of a solvent cannot be predicted from its chlorine content or chemical stmcture. For example, 1,1,1-trichloroethane is one of the least toxic metal-cleaning solvents and has a recommended threshold limit value (TLV) of 350 ppm. However, the 1,1,2-trichloroethane isomer is one of the more toxic chloriaated hydrocarboas, with a TLV of only 10 ppm. 

Release of trichloroethylene also occurs at treatment and disposal sites. Water treatment facilities may release trichloroethylene from contaminated water through volatilization and air-stripping procedures (EPA 1985e). Trichloroethylene is also released to the atmosphere through gaseous emissions from landfills. The compound may occur as either an original contaminant or as a result of the decomposition of tetrachloroethylene. Trichloroethylene has also been detected in stack emissions from the incineration of municipal and hazardous waste (James et al. 1985 Oppelt 1987). 

Okouchi S. 1986. Volatilization coefficient for stripping trichloroethylene, 1,1,1-trichloroethane and tetrachloroethylene from water. Water Sci Technol 18 137-138. 

The presence of 0.5% of trichloroethylene as impurity in tetrachloroethylene during unheated drying over solid sodium hydroxide caused generation of dichloroacety-lene. After subsequent fractional distillation, the volatile fore-run exploded. 

In a continuous-flow mixed-film methanogenic column study, tetrachloroethylene degraded to trichloroethylene with traces of vinyl chloride, dichloroethylene isomers, and carbon dioxide (Vogel and McCarty, 1985). In a static-culture-flask screening test, tetrachloroethylene (5 and 10 mg/L) was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum. Significant degradation with gradual adaptation was observed after 28 d of incubation. The amount lost due to volatilization after 10 d was 16 to 23% (Tabak et al., 1981). 

The volatilization half-life of tetrachloroethylene (1 mg/L) from water at 25 °C using a shallow-pitch propeller stirrer at 200 rpm at an average depth of 6.5 cm was 25.4 min (Dilling, 1977). 

Volatile organic compounds (VOCs), especially trihalomethanes, are frequently found in drinking water due to the chlorination of humic acids. When UV irradiation is applied to the pre-ozonation of humic acids, the decomposition of VOC precursors increases (Hayashi et al., 1993). The ozonation rates of compounds such as trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, 1,2-dichloroethane, and 1,2-dichloropropane were found to be dependent on UV intensity and ozone concentration in the aqueous phase by Kusakabe et al. (1991), who reported a linear relationship between the logarithmic value of [C]/[C0] and [03]f for 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene. The other two organochlorines followed the same first-order kinetics with and without UV irradiation (Kusakabe et al., 1991). Thus, the decomposition rate can be expressed as ... 

Tetrachloroethylene is a volatile liquid whose odor is detectable at ca. 50 ppm. It is an excellent solvent, and is widely used in dry... 

As shown in Figure 1.17, there are three possible dichloroethylene compounds, all clear, colorless liquids. Vinylidene chloride forms a copolymer with vinyl chloride used in some kinds of coating materials. The geometrically isomeric 1,2-dichloroethylenes are used as organic synthesis intermediates and as solvents. Trichloroethylene is a clear, colorless, nonflammable, volatile liquid. It is an excellent degreasing and dry-cleaning solvent and has been used as a household solvent and for food extraction (for example, in decaffeination of coffee). Colorless, nonflammable liquid tetrachloroethylene has properties and uses similar to those of trichloroethylene. Hexachloro-butadiene, a colorless liquid with an odor somewhat like that of turpentine, is used as a solvent for higher hydrocarbons and elastomers, as a hydraulic fluid, in transformers, and for heat transfer. 

Pedit et al. [226] used a kinetic model for the scale-up of ozone/hydrogen peroxide oxidation of some volatile organochlorine compounds such as trichloroethylene and tetrachloroethylene. The kinetic model was applied to simulate the ozone/hydrogen peroxide treatment of these pollutants in a full-scale demonstration plant of the Los Angeles Department of Water and Power. The authors confirmed from the model that the reaction rate of the pollutant with ozone was several orders of magnitude lower than that with the hydroxyl radical. When considering that the natural organic matter acts as a promoter of hydroxyl radicals, the ozone utilization prediction was 81.2%, very close to the actual 88.4% experimentally observed. 

Tetrachloroethylene is used as a solvent. It is highly volatile and, for this reason, has been found only in groundwaters. Its odor threshold in water is 300 pg L and it is classified by the EPA as a probable human carcinogen (Group B2). 

The photolysis of hexachloroacetone in the vapour phase has been studied by Hautecloque and in the liquid by Haszeldine and Nyman . The volatile products of the gas phase reaction were carbon tetrachloride, tetrachloroethylene, hexachloroethane and carbon monoxide, and the quantum yield for CO formation was 0.5 at 275 °C and 2 3130 A. These results suggest that primary processes of both Type 1 and Type 2 are occurring and that carbon monoxide is not readily formed from the trichloroacetyl radical... 

The US EPA has identified many types of organic compounds in our water supplies. Some of the organic compounds are volatile, and, as a result, aeration would be a good process selection for removing them from water. For compounds that are non-volatile, adsorption would be a better process selection than aeration for their removal from the water. Some common volatiles include trihalomethanes, which have already been discussed chlorobenzene, 1,1,1-trichloroethane, tetrachloroethylene, and trichloroethylene. Aeration can achieve up to 95% removal of these compounds. 

Volatile organic contaminants such as benzene, carbon tetrachloride, chlorobenzene, o-dichloro-benzene, p-dichlorobenzene, 1,1-dichloroethylene, cis-l,2-dichloroethylene, tra s-l,2-dicholoro-ethylene, dichloromethane, 1,2-dichloroethane 1,2-dichloropropane, ethylbenzene, styrene, tetrachloroethylene, 1,2,4-trichlorobenzene, 1,1,1,-trichloroethane, 1,1,2-trichloroethane, trichloroethylene, toluene, vinyl chloride, and xylenes. 

Ozone-based AOPs are being used increasingly to treat landfill leachates. " They are also used for ground-water treatment to destroy trichloroethylene (TCE), tetrachloroethylene, and pentachlorophenol. In addition, they are used for groundwater remediation at Superfund sites in the United States to destroy volatile organic compounds and benzidines. Another application of ozone-based AOPs involves their use at U.S. ammunition plants to destroy explosives. ... 

As shown in Table n, chloroform and carbon tetrachloride have about the same Henry s Law constant above oil, even though carbon tetrachloride is considerably more volatile above water than chloroform. The high distribution coefficient for carbon tetrachloride significantly reduces the Henry s Law constant for the oil phase. The relatively high partial pressure of tetrachloroethylene above water is significantly reduced in oil due to the large distribution coefficient... 

In situations where a combination of contaminants is involved, the least volatile component (in the case of Table III, tetrachloroethylene) controls the design of the stripper. Once the operating temperature and pressure is set, the exiting mole fraction of tetrachloroethylene is determined from its partial pressure. The mole fraction of the strip gas and its minimum flow rate can then calculated. 

The detection of urinary metabolites has also been used to detect occupational exposure or to confirm inhalation of volatile substances. Urinary metabolites such as phenol (benzene metaboEte), trichloroacetic acid (tetrachloroethylene), hippuric acid (toluene) and methylhippuric acid (xylene) have been detected and measured. Results are often... 

Because of their volatility most aliphatics - e.g. chloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene -occur at low or nondetectable levels in sediments. 

Block 2 - the heavy metal group (e.g. arsenic, mercury, cadmium) and lightly volatile halogenated hydrocarbons (e.g. tetrachloroethylene), the broad group of pesticide substances (e.g. triazine, phenoxy alkane carbon acids) and polycyclic aromatic hydrocarbons (PAHs). 

In addition to gases produced naturally in the environment, estuaries tend to be enriched in byproducts of industry and other human activity. A few studies have investigated volatile organic pollutants such as chlorinated hydrocarbons (chloroform, tet-rachloromethane, 1,1-dichloroethane, 1,2-dichlor-oethane, 1,1,1-trichloroethane, trichloroethylene and tetrachloroethylene) and monocyclic aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene and m- and p-xylene). Concentrations of VOCs are controlled primarily by the location of the sources, dilution of river water with clean marine water within the estuary, gas exchange, and in some cases, adsorption onto suspended or settling solids. In some cases (for example, chloroform) there also may be natural biotic sources of the gas. Volatilization to the atmosphere can be an important cleansing mechanism for the estuary system. Since the only estuaries studied to date are heavily impacted by human activity (the Elbe and... 

There was, however, a study suggesting immunological effects in humans with chronic exposure to a solvent-contaminated domestic water supply. Several wells in Woburn, Massachusetts, were contaminated by a variety of solvents. The two main volatile chlorinated hydrocarbons measured before well closure were trichloroethylene (267 ppb) and tetrachloroethylene (21 ppb) (Byers et al. 1988). A potential association between water contamination in Woburn and cases of childhood leukemia is discussed in Section 2.2.2.8. 

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