Dechlorination and

Mercury cells are operated to maintain a 21—22 wt % NaCl concentration in the depleted brine and thus preserve good electrical conductivity. The depleted brine is dechlorinated and then resaturated with soHd salt prior to recycling back to the electroly2er. 

In the membrane process, the chlorine (at the anode) and the hydrogen (at the cathode) are kept apart by a selective polymer membrane that allows the sodium ions to pass into the cathodic compartment and react with the hydroxyl ions to form caustic soda. The depleted brine is dechlorinated and recycled to the input stage. As noted already, the membrane cell process is the preferred process for new plants. Diaphragm processes may be acceptable, in some circumstances, but only if nonasbestos diaphragms are used. The energy consumption in a membrane cell process is of the order of 2,200 to 2,500 kilowatt-hours per... 

Considerable attention has been directed to dehalogenation mediated by corrinoids and porphyrins in the presence of a chemical reductant (references in Gantzer and Wackett 1991 Glod et al. 1997 Workman et al. 1997). Illustrations are provided by the dechlorination and elimination reactions carried out by titanium(III) citrate and hydroxocobala-min (Bosma et al. 1988 Glod et al. 1997). The involvement of corrinoids and porphyrins is consistent with the occurrence of analogous mechanisms for biological reactions that... 

Jagnow G, K Haider, P-C Ellwardt (1977) Anaerobic dechlorination and degradation of hexachlorocyclo-hexane by anaerobic and facultatively anaerobic bacteria. Arch Microbiol 115 285-292. 

Daphnia magna has been shown to bring about dechlorination and limited oxidation of heptachlor (Figure 2.25) (Feroz et al. 1990). 

Apajalahti JH, MS Salkinoja-Salonen (1987) Dechlorination and para-hydroxylation of polychlorinated phenols by Rhodococcus chlorophenolicus. J Bacteriol 169 675-681. 

Mohn WW, JM Tiedje (1991) Evidence for chemiosmotic coupling of reductive dechlorination and ATP synthesis in Desulfomonile tiecljei. Arch Microbiol 157 1-6. 

Ingenious experiments to which reference has already been made have used addition of specific PCB congeners that are more readily dechlorinated to prime dechlorination at specific positions (Bedard and Quensen 1995). They have been extended to the use of dibrominated biphenyls in the presence of malate to stimulate dechlorination of the hexachloro- to nanochlorobiphenyls (Bedard and Quensen 1995). Results from these experiments provide valuable evidence of important differences between anaerobic dechlorination and anaerobic debromination, and the greater facility of the latter. 

Mikesell MD, S A Boyd (1986) Complete reductive dechlorination and mineralization of pentachlorophenol by anaerobic microorganisms. Appl Environ Microbiol 52 861-865. 

Specific effluents have also been subjected to WRF-mediated remediation studies. Decolourization, dechlorination and detoxification of highly toxic bleach plant effluents derived from the pulp and paper industry have been reported [26-28], while degradation and decolourization of synthetic dyes due to the non-specificity of the LMEs have been widely documented [29, 30], Likewise, treatment of the acidic, phenolic-rich olive oil mill wastewater has shown COD reduction, decolourization and dephenolization [31-34],... 

Biotransformation of PCP in mammals occurs via conjugation, reductive dechlorination, hydrolytic dechlorination, and oxidation. In the process, a number of metabolites are formed, some of which are demonstrably toxic (Renner and Hopfer 1990 Jansson and Jansson 1991 Reigner et al. 1991). Metabolites of PCP found in rat urine and identified (acute oral LD50 to mice, in mg/kg BW) include (Renner and Hopfer 1990) ... 

Endrin and endrin aldehyde are listed as hazardous wastes and disposal of wastes is controlled by a number of federal regulations. Past disposal methods have included landfills (EPA 1987c). Chemical treatment (reductive dechlorination) and incineration are possible disposal methods (HSDB 1995 IRPTC 1985). Existing information on disposal appears adequate. No information was found on disposal of endrin ketone however, because endrin is no longer used in the United States, current levels of endrin ketone in wastes should be minimal and additional information on disposal is not needed. 

Bouwer and McCarty [374] suggested 1,1,2-TCA is an intermediate of TeCA transformation in continuous-flow column experiments and TCE as an intermediate in a batch experiment under methanogenic conditions. Those transformations are reductive dechlorination and dehydro chlorination, respectively. 

Schanke and Wackett [379] reported TeCA degradation by transition-metal coenzymes. cDCE (53%), tDCE (29%), VC (14%), ethylene (1%), and traces of 1,1,2-TCA were the products from this abiotic transformation with vitamin B12 and titanium(III) citrate. Both dechlorination and dichloroelimination had occurred the major route of degradation was reductive dihaloelimina-tion. 

Despite the environmental stability of these compounds, a number of reports have indicated that under reducing conditions prevailing in sediments dioxins may undergo transformation reactions, including dechlorination. The potential importance of reductive dechlorination, and perhaps one of the reasons for the emphasis on this transformation process, is illustrated by recent evidence that... 

TCDD (perz-dechlorination), from one, which does not produce this tetra-CDD isomer (perz-lateral dechlorination). The relative contribution of each pathway (i.e., the ratio of 2,3,7,8- to other tetra-substituted congeners) observed is dependent on the system tested, whereby the presence of phenolic compounds appears to shift the pathway toward peri-dechlorination and enhances the total yield of lesser chlorinated products [433]. 

In conclusion, the oxamic acid derivative is produced by two distinct metabolic pathways, namely by oxidative and hydrolytic dechlorinations. In contrast, the primary alcohol metabolite 11.41 can be produced only by hydrolytic dechlorination and is, thus, an unambiguous marker of this pathway. The alcohol 11.41 is a known urinary metabolite of chloramphenicol in humans. 

CASRN 127-20-8 molecular formula C3H3Cl2Na02 FW 164.95 Soil. Undergoes dechlorination and the liberation of carbon dioxide in soil. The residual activity is limited to approximately 3-4 months (Hartley and Kidd, 1987). The average half-life for dalapon-sodium in soil incubated in the laboratory under aerobic conditions was 15 d (Namdeo, 1972). 

MnP catalyzes hydrogen-peroxide-dependent oxidation of Mn to Mn, which in turn oxidizes phenolic components of lignin [102]. Oxidative demethylation, dechlorination, and decolorization of bleach plant effluent by the MnP of Phanerochaete chrysosporium has been demonstrated [103,104]. 

Racemic -amino acids, namely 3,3-ethano- -alanine (193 a) and its spiro-cyclopropanated analog 193b, have been prepared by simple one-step hydrogenolytic reduction and deprotection of the primary Michael adducts 94 b and 94 d (Scheme 57) [9,21b]. As methyl esters cannot be deprotected under these conditions, only reductive dechlorination and debenzylation was observed for compounds 91t,u (Scheme 57) [7k]. This looks promising for the construction of... 

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