1.2.4- trichlorobenzene, degradation

Valnes of were measnred for the degradation of trichlorobenzenes (Griebler et al. 

For aerobic degradation by Pseudomonas sp. strain P51, which carried out degradation by dioxygenation, the valnes were not significant. In contrast, the isotope enrichment factor (e) for anaerobic dechlorination by Dehalococcoides sp. strain CDBl, which produced 1,3-dichlorobenzene from 1,2,3-trichlorobenzene, was -3.4 ppm, and for 1,2,4-trichlorobenzaene, which produced 1,4-dichlorobenzene, was -3.2 ppm. 

Middeldorp PJM, De Wolf J, Zehnder AJB, Schraa G (1997) Enrichment and properties of a 1,2,4-trichlorobenzene-dechlorinating methanogenic microbial consortium. Appl Environ Microbiol 63 1225-1229 Miller ME, Alexander M (1991) Kinetics of bacterial degradation of benzylamine in a montmorillonite suspension. Environ Sci Technol 25 240-245 Montville R, Schaffner DW (2003) Inoculum size influences bacterial cross contamination between surfaces. Appl Environ Microbiol 69 7188-7193 Mortland, MM (1970) Clay-organic complexes and interactions. Advances in Agronomy 22 75-117... 

Apart from nitrobenzene, trichlorobenzene in particular was the preferred solvent up until a few years ago. It has now been replaced by other solvents such as high-boiling hydrocarbons (kerosene, naphthalene) and also alcohols and glycols, because traces of polychlorinated biphenyls may be formed. These are not easily degradable. With hydrocarbons, however, the possibility of fire and explosion must be considered in designing suitable production units. 

Photolytic. When an aqueous solution containing a-BHC was photooxidized by UV light at 90-95 °C, 25, 50, and 75% degraded to carbon dioxide after 4.2, 24.2, and 40.0 h, respectively (Knoevenagel and Himmelreich, 1976). In basic, aqueous solutions, a-BHC dehydrochlorinates forming pentachlorocyclohexene before being transformed to trichlorobenzenes. In a buffered aqueous solution at pH 8 and 5 °C, the calculated hydrolysis half-life is 26 yr (Ngabe et al., 1993). 

Soil. Lindane degraded rapidly in flooded rice soils (Raghu and MacRae, 1966). In moist soils, lindane biodegraded to (y-PCCH) (Eisner et al., 1972 Kearney and Kaufman, 1976 Fuhremann and Lichtenstein, 1980). Under anaerobic conditions, degradation by soil bacteria yielded y-BTC and a-BHC (Kobayashi and Rittman, 1982). Other reported biodegradation products include pentachlorocyclohexane, pentachlorobenzene, tetrachlorocyclohex-l-enes, and tetrachloro-benzenes (Moore and Ramamoorthy, 1984). Incubation of lindane for 6 wk in a sandy loam soil under flooded conditions yielded y-TCCH, y-2,3,4,5,6-pentachlorocyclohex-l-ene, and small amounts of 1,2,4-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,3,5-, and/or 1,2,4,5-tetrachloro-benzene (Mathur and Saha, 1975). Incubation of lindane in moist soil for 8 wk yielded the follow-... 

Biological. Under aerobic conditions, soil microbes are capable of degrading 1,2,3-trichlorobenzene to 1,2- and 1,3-dichlorobenzene and carbon dioxide (Kobayashi and Rittman, 1982). A mixed culture of soil bacteria or a Pseudomonas sp. transformed 1,2,3-trichlorobenzene to 2,3,4-, 3,4,5-, and 2,3,6-trichlorophenol (Ballschiter and Scholz, 1980). 

Plant. Degrades in plants to 4-hydroxy-2,5,6-trichloroisophthalonitrile (Hartley and Kidd, 1987), l,3-dicyano-4-hydroxy-2,5,6-trichlorobenzene, and l,3-dicarbamoyl-2,4,5,6-tetrachloro-benzene (Rouchaud et al., 1988). No evidence of degradation products were reported in apple foliage 15 d after application. The half-life of chlorothalonil was 4.1 d (Gilbert, 1976). 

A reliable procedure for determination of molecular parameters number, weight and z-averages of the molecular weight (Mj, i = n, w and z respectively) for polyethylenes, PE, by means of Size Exclusion Chromatography, SEC, has been developed. The Waters Sci. Ltd. GPC/LC Model 150C was used at 135 C with trichlorobenzene, TCB, as a solvent. The standard samples as well as commercial stabilized and not stabilized PE-resins were evaluated. The effects of sampling, method of solution preparation, addition of antioxidant(s), thermal and shear degradation were studied. The adopted procedure allows reproducible determination of and M , with a random error of 4% and M2, with 9%, within 2 to 72 hrs from the initial moment of preparation of solutions. 

Despite the superficially structural complexity of the CPC molecule, it is prepared with comparative ease (15) (see PHTHALOCYANINE COMPOUNDS). The preferred manufacturing process starts with phthalic anhydride and is carried out in a variety of solvents, trichlorobenzene having been the preferred solvent, but it has been replaced with high boiling hydrocarbons or glycols in order to avoid the formation of the hazardous and poody degradable polychlorinated biphenyls. 

Direct electrolytic dechlorination of 9-chloroanthracene at a mercury electrode occurs at about -1.65 V (see) in a layer of adsorbed cetyltrimethylammonium bromide on the electrode surface233. Similarly, electrochemical degradation of trichloroethylene in acetonitrile resulted in quantitative conversion to chloroacetylene, which was reduced further to acetylene at a more negative reduction potential (-2.8 V) in 96% yield234. Reductive destruction of 1,3,5-trichlorobenzene in the cathode compartment could be observed235. Electrochemical methods presumably can be used for decontamination of chemical warfare agents such as mustard derivatives as an alternative to the chemical methods such as base-catalyzed dehydrohalogenation236. 

Uchida, H., S. Katoh and M. Watanabe (1998). Photocatalytic degradation of trichlorobenzene using immobilized Ti02 films containing poly(tetrafluoroethylene) and platinum metal catalyst. Electrochimica Acta, 43(14-15), 2111-2116. 

Two contrasting results may be instructive. Experiments with chlorinated benzenes in which the effect of substrate concentration was examined in batch cultures and in recirculating fermentors showed that although substrates could be degraded completely in the former, a residual concentration of the substrate persisted in the latter (van der Meer et al. 1992). On the other hand, experiments using Burkholderia sp. strain PS14 failed to detect residual concentrations >0.5 nM after mineralization of 1,2,4,5-tetra- and 1,2,4-trichlorobenzene at concentrations of 500 nM (Rapp and Timmis 1999). These results are highly relevant in the context of bioremediation (Chapter 8, Section 8.1.2). 

An elimination reaction is apparently one of the steps in the degradation of y-hexachloro[fleece] cyclohexane from which pentachlorobenzene (Tu 1976) or y-2,3,4,6-tetrachlorocyclohex-l-ene may be formed (Jagnow et al. 1977) (Figure 6.64). The formation of both 2,5-dichlorophenol and 2,4,5-trichlo-rophenol during the aerobic degradation of y- exa.ch om[aaaeee]cyclohexane by Pseudomonas paucimobilis presumably occurs by comparable elimination reactions (Senoo and Wada 1989) and further details of the transformation that produces also 1,2,4-trichlorobenzene have been provided (Nagasawa et... 

Inherent biodegradabilty also appears to affect the adaptation process. Substrates which are easily metabolized may not exhibit an adaptive response because initial rates of degradation are sufficient. For instance, 2-chlorophenol was readily metabolized in both unexposed and preexposed groundwater microcosms (46). More recalcitrant compounds require an adaptive period. Thus, 2,4,5-trichlorophenol added to microcosms similar to those used for the 2-chlorophenol experiments was degraded rapidly after a 1-day lag in the preexposed microcosm. A 6-day lag was required in the unacclimated microcosm. Other substrates show no adaptive response, such as chlorobenzene or 1,2,4-trichlorobenzene (43). 

Level II Model The added refinement involves accounting for losses from compartments either by advection or reaction. A steady state is achieved where input is balanced by the loss from the system, but the compartments remain at equilibrium as indicated by the fluid height in the tank analogy (Fig. 10.9). Quantities defining the loss of 1,2,3-trichlorobenzene from the system by advection and reaction are compiled in Table 10.8. Photochemical reactions would be the most likely processes involved in air and water, while microbial degradation would be active in soil and bottom sediments, and the use of first-order rate constants (h ) is an appropriate approximation. 

Sample Preparation A small sample of polymer is weighed (10 mg) and placed in a 15-ml stainless steel vial. Then, 10 ml of 1,2,4-trichlorobenzene is added to the vial and the sample is placed in an oven at 120 °C for 3 h. A stabilizing agent, such as Irganox 1010, should be added to the solvent to avoid degradation of the polymer during the dissolution period. Once the polymer is solubilized, a stainless steel filter is placed on top of the stainless steel vial the filter is pushed down, thus the solution is filtered in this step, any contaminants are removed from the solution. 

PPS. Polymer is recovered by washing with water to remove the salt and solvent, and then dried. The pol)merization (Eq. 1) is very sensitive to many process variables that must be monitored to avoid polymer degradation. Molecular weight of the PPS can be increased by adding sodium acetate or other alkali metal carboxylate salts to the polymerization mixture before dehydration. Also, a small amount of a trifunctional comonomer, such as 1,2,4-trichlorobenzene, can be added with the dichlorobenzene as a chain branching agent. 

Grinshpun and coworkers [9-11] have studied the dissolution behavior of both PE and isotactic PP in trichlorobenzene and other solvents. For work with isotactic PP they added 0.1% Irgafos D13-168 (2,4-di-tert-butylphenylphosphite) and 0.1% lonol (butylated hydroxytoluene) to the sample solutions. At dissolution temperatures >145°C degradation... 

VOCARB traps are special combinations of the adsorption materials Carbopack (GCB) and Carboxen (carbon molecular sieve). These combinations have been optimized in the form of VOCARB 3000 and VOCARB 4000 for volatile and lessvolatile compounds respectively, corresponding to the ERA methods 624/1624 and 542.2 (Supelco, 1992). VOCARB 4000 exhibits higher adsorptivity for less volatile components, such as naphthalenes and trichlorobenzenes. However, it shows catalytic activity towards 2-chloroethyl vinyl ether (complete degradation ), 2,2-dichloropropane, bromoform and methyl bromide. 

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