Cometabolic decomposition of trichloroethylene by recombinant hydroxyquinol 1,2-dioxygenase

Potential for co-metabolic oxidation of TCE and evidence for its occurrence in a large-scale aquifer survey

Decomposition of trichloroethylene and 2,4-dichlorophenol by ozonation in several organic solvents

Preparation of TiO 2 film by the MOCVD method and analysis for decomposition of trichloroethylene using in situ FT-IR spectroscopy

Influences of H2 and O2 and in situ Ca(OH)2 absorption on nonthermal plasma decomposition of trichloroethylene in N2

A nonthermal plasma processing combined with Cr2O3/TiO2 catalyst was applied to the decomposition of trichloroethylene (TCE). A dielectric barrier discharge reactor was used as the nonthermal plasma reactor. The effects of the reaction temperature and input power on the decomposition of TCE and the formation of byproducts including HCl, Cl2, CO, NO, NO2 and O3 were examined. With an identical input power, the increase in the reactor temperature lowered the decomposition of TCE. The presence of the catalyst downstream the plasma reactor not only enhanced the decomposition of TCE but also affected the distribution of byproducts significantly. However any synergetic effect as a result of the combination of the nonthermal plasma with the catalyst was not observed, i.e., the TCE decomposition efficiency in the plasma-catalyst combined system was almost similar to the sum of those obtained with each process. To improve the decomposition of TCE argon as a plasma-assisting gas was added to the feeding gas and a large enhancement in the TCE decomposition was achieved.

The atmospheric pressure non-thermal plasma is very active and can decompose various toxic gaseous materials. The authors are engaged in decomposing various VOCs (volatile organic compounds) by using the high pressure non-thermal plasma. In order to improve the decomposition energy efficiency of the plasma reactor, new manganese-dioxide supported alumina spheres of 3 mm in diameter were fabricated as the new catalyst which can decompose the ozone very well even at the room temperature. The non-thermal plasma processed air with/without dilute VOCs contains much ozone which is easily decomposed by that new catalyst. At that ozone decomposition process in the catalyst, trichloroethylene (TCE) is also oxidized very well. That TCE decomposition mechanism is a little bit different with the TCE decomposition by the non-thermal plasma directly. If the specific energy density (SED: input discharge energy, Joule, per 1 litter gas) is only 11 J/L, the TCE decomposition efficiency is more than 99 % in authors experiment. However, the improvement of the carbon balance (more than 99 % carbon of TCE is oxidized to carbon oxide) needs very large SED of 90 J/L at present. Some trials to improve the TCE decomposition efficiency were also examined.

A comparative study on the contribution of cytochrome P450 isozymes to metabolism of benzene, toluene and trichloroethylene in rat liver

Physiologically Based Pharmacokinetic Modeling of Inhaled Trichloroethylene and Its Oxidative Metabolites in B6C3F1Mice

The effect of the structure of a mixture of industrially produced iron and iron oxide on the decomposition of trichloroethylene (TCE) was investigated by gas chromatography, scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, X-ray diffractometry, and 57Fe-Mossbauer spectroscopy. The concentration of 10 mg L−1 TCE aqueous solution decreased to 0.41, 0.52, 0.26, and 0.09 mg L−1 when stirred for 7 days with iron–iron oxide mixtures having mass ratios of 2:8, 3:7, 4:6, and 5:5, respectively. The Mossbauer spectra of the mixtures after leaching were composed of two sextets with respective isomer shifts (δ) and internal magnetic fields (H) of 0.29±0.01 mm s−1 and 48.8±0.1 T, and 0.64±0.01 mm s−1 and 45.5±0.1 T, attributed to the Fe3+ species in tetrahedral (Td) and the Fe2+ and Fe3+ mixed species (Fe2.5+) in octahedral (Oh) sites, respectively. Mossbauer spectra of a 3:7 mass ratio iron–iron oxide mixture showed a gradual decrease in the absorption area (A) of zero valent iron (Fe0) from 40.6. to 12.6, 13.2, 3.8 2.8, and 1.0±0.5 % and an increase in A of Fe3O4 from 31.8 to 59.4, 71.4, 93.2, 95.6, and 98.0±0.5 % after leaching with 10 mg L−1 TCE aqueous solution for 1, 2, 3, 7, and 10 days, respectively. Consistent values of the first-order rate constant were calculated as 0.32 day−1 for Fe0 oxidation, 0.34 day−1 for Fe3O4 production, and 0.30 day−1 for TCE decomposition, which indicates that the oxidation of Fe0 was the rate-controlling factor for Fe3O4 production and TCE decomposition. It is concluded from the experimental results that an iron–iron oxide mixture is very effective for the decomposition of TCE.

The present study investigated the degradation of trichloroethylene (TCE) in sand suspensions by Fenton-like reaction with magnetite (Fe3O4) in the presence of various chelators at circumneutral pH. The results showed that ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) greatly improved the rate of TCE degradation, while [S,S]-ethylenediaminedisuccinic acid (s,s-EDDS), malonate, citrate, and phytic acid (IP6) have minimal effects on TCE degradation. Quenching tests suggested that TCE was mainly degraded by hydroxyl radical (HO·) attack, with about 90% inhibition on TCE degradation by the addition of HO· scavenger 2-propanol. The presence of 0.1-0.5% Fe3O4/sand (w/w) contributed to 40% increase in TCE degradation rates. In particular, the use of chelators can avoid high concentrations of H2O2 required for the Fenton-like reaction with Fe3O4, and moreover improve the stoichiometric efficiencies of TCE degradation to H2O2 consumption. The suitable concentrations of chelators (EDTA and NTA) and H2O2 were suggested to be 0.5 and 20mM, respectively. Under the given conditions, degradation rate constants of TCE were obtained at 0.360h-1 with EDTA and 0.526h-1 with NTA, respectively. Enhanced degradation of TCE and decreased usage of H2O2 in this investigation suggested that Fenton-like reaction of Fe3O4 together with NTA (or EDTA) may be a promising process for remediation of TCE-contaminated groundwater.

Ozonation of trichloroethylene in acetic acid solution with soluble and solid humic acid

A Physiologically Based Pharmacokinetic Model for Trichloroethylene and Its Metabolites, Chloral Hydrate, Trichloroacetate, Dichloroacetate, Trichloroethanol, and Trichloroethanol Glucuronide in B6C3F1 Mice

Trichloroethylene (TCE) is a prevalent occupational and environmental contaminant that has been reported to cause a variety of toxic effects. Here, we have undertaken studies to test the hypothesis that TCE exposure adversely affects sperm function and fertilization. Sperm retrieved from mice exposed to TCE (1000 ppm) by inhalation for 1 to 6 weeks were incubated in vitro with eggs isolated from superovulated female mice. The number of sperm bound per egg was significantly decreased when mice were exposed to TCE for 2 and 6 weeks but not at exposures of 1 and 4 weeks. In vivo fertilization was also determined in superovulated female mice mated with males exposed to TCE for 2 to 6 weeks. The percentages of eggs fertilized, as assessed by the presence of two pronuclei, were significantly decreased after 2 and 6 weeks of TCE exposure. A slight but insignificant decrease was observed after 4 weeks of TCE exposure. The direct effects of TCE and its metabolites, chloral hydrate (CH) and trichloroethanol (TCOH), on in vitro sperm-egg binding were also investigated. Sperm-egg binding was significantly decreased when sperm were pretreated with CH (0.1-10 microg/mL). Significantly lower levels of sperm-egg binding were also detected with TCOH (0.1-10 microg/mL), although the decreases were not as pronounced as those for CH. These results showed that TCE exposure leads to impairment of sperm fertilizing ability, which may be attributed to TCE metabolites, CH, and TCOH.

Plasma chemical behavior of trichloroethylene (TCE) was investigated with a packed-bed ferroelectric pellet reactor and a pulsed corona reactor. Volatile byproducts were identified by gas chromatography and mass spectrometry (GC-MS), and it was shown that reactor type, TCE concentration, flow rate, background gas, and moisture affected TCE decomposition efficiency and product distribution. Byproduct distributions in nitrogen and the negative effect of oxygen and moisture on TCE decomposition efficiency show that TCE decomposition proceeds via initial elimination of chlorine and hydrogen atoms, the addition of which to TCE accelerates its decomposition. Active oxygen species like OH radical is less likely involved in the initial step of TCE decomposition in plasma. Triplet oxygen molecules (/sup 3/O/sub 2/) scavenge intermediate carbon radicals derived from TCE decomposition to give much lower yields of organic byproducts.

Use of specific gene analysis to assess the effectiveness of surfactant-enhanced trichloroethylene cometabolism