Perchloroethylene degradation

Alessi DS, Li Z. Synergistic effect of cationic surfactants on perchloroethylene degradation by zero-valent iron. Environ Sci Technol 2001 35 3713-3717. 

Fig. 7 Scheme of perchloroethylene degradation in soU, water, and air and corresponding fractions of formation. Reprinted with permission from [5], p 38. (2003) Society for Risk Analysis... 

Acetate and triacetate are essentially unaffected by dilute solutions of weak acids, but strong mineral acids cause serious degradation. The results of exposure of heat-treated and untreated triacetate taffeta fabrics to various chemical reagents have been reported (9). Acetate and triacetate fibers are not affected by the perchloroethylene dry-cleaning solutions normally used in the United States and Canada. Trichloroethylene, employed to a limited extent in the UK and Europe, softens triacetate. 

Franklin J (1994) The atmospheric degradation and impact of perchloroethylene. Toxicol Environ Chem 46 169-182. 

Hirvonen et al. (1995) evaluated the feasibility of the UV/H202 process for the removal of trichloroethylene (TCE) and erythromycin (perchloroethylene [PCE]) in contaminated groundwater. The formation of chloroacetic acids (CAs) was used as an indication of partial degradation. The dominant byproduct, dichloroacetic acid (DCA), accounted for the major part of the total yield of CAs. The observed concentrations of trichloroacetic acid (TCA) and DCA were relatively low compared with the total amount of TCE and PCE degraded. The effect of initial concentrations of the parent compounds, hydrogen peroxide, and bicarbonate on the yield of by-product was inves-... 

Fukami N, Yosida M, Lee B-D, Taku K, Ho-SOMI M (2001) Photocatalytic Degradation of Gaseous Perchloroethylene Products and Pathway, Chenwsphere 42 345-350. 

The coexistence of various pollutants does not have to be deleterious, but, in certain cases, can be quite beneficial. The first evidence for this claim came probably from the work of Lichtin et al. (1994) who found that the edition of 0.03% by volume to an air-stream containing 0.1% iso-octane caused an enhancement in the photocatalytic oxidation of the latter. Likewise, a significant rate enhancement was recorded in the photocatalytic degradation of chloroform and dichloromethane in the presence of TCE. Similar effects were recorded also with other chlorinated olefins, such as perchloroethylene (PCE) and trichloropropene (TCP), which enhanced the photooxidation of toluene in a manner similar to that of TCE (Sauer et al., 1995). 

Chapter 7 reports a scaling-up procedure for photocatalytic reactors. The described methodology uses a model which involves absorption of radiation and photocatalyst reflection coefficients. The needed kinetics is obtained in a small flat plate unit and extrapolated to a larger reactor made of three concentric photocatalyst-coated cylindrical tubes. This procedure is applied to the photocatalytic conversion of perchloroethylene in air and to the degradation of formic acid and 4-chlorophenol in water. 

The removal of perchloroethylene solvents such as the very toxic trichloroethylene (TCE) from soil and water is a rather difficult problem [331]. A bench-scale study was conducted in TCE-contaminated sand columns. The following operation was tested. Foam obtained using the anionic surfactant Steol CS-330 was injected in a pulsed operation, after which artificial groundwater followed, and then foam again. The result was 75% of the initial TCE content. After the TCE-degrading bacterial strain ENV 435 had been added with the second pulse of foam, the result of the treatment was 95-99%. 

Trichloroethylene and perchloroethylene are susceptible to oxidative breakdown which is accelerated by high temperatures and exposure to ultraviolet (UV) light. The addition of antioxidants eliminates the potential of oxidative degradation. 

The transformations of the chlorinated hydrocarbons perchloroethylene (PCE), trichloroethylene (TCE), and 1,1,1-trichloroethane are illustrative of these types of reactions. Cis- and tranj -l,2-dichloroethylene (1,2-DCE), 1,1-dichloroethylene (1,1-DCE), and VC are often found in well water which has been contaminated only with tetrachloroethylene and/or TCE [48]. Some of the transformations of PCE and TCE are biologically catalyzed and occur in soil and sediment, while others are believed to occur in groundwater [49, 50]. 1,1,1-Trichloroethane hydrolyzes to 1,1-DCE in groundwater [51]. Figure 8.1 shows the degradation sequence of tetrachloroethylene and TCE. 

Imoberdorf G, Irazoqui H, Cassano A, Alfano O. Modelling of a multi-annular photoieactor for the degradation of perchloroethylene in gas phase... 

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