Rapid Dechlorination Research Articles

Dechlorination activity (cross‐acclimation) of freshwater sediments adapted to whom it may concern: It may concern: Mono‐ and di‐chlorophenols

Abstract The reductive dechlorination of chlorophenols (CPs) in sediment slurries (10% solids) adapted to dechlorinate mono‐ and di‐CPs (DCP) was investigated to define the regiospecificity of the dechlorination reaction. Unadapted sediment slurries amended with various ortho‐substituted CPs exhibited lag periods ranging from 8 to 12 days before the onset of dechlorination. In contrast, 2‐ and 3‐CP as well as 2,3‐ and 2,4‐DCP were dechlorinated without a lag period by sediments adapted to transform 2‐CP. Dechlorination of 4‐CP was not observed after incubation for 35 days. Adaptation to 2‐CP, therefore, enhanced the onset of dechlorination of 3‐CP and all ortho‐substituted CPs tested. Dechlorination of 2‐CP, 3‐CP, 2,3‐DCP, and 3,4‐DCP was also effected without a lag period by sediments adapted to transform 3‐CP. Sediments adapted to dechlorinate individual DCPs (2,3‐, 2,4‐, and 3,4‐DCP) exhibited dechlorination of 2‐CP, 2,3‐, 2,4‐, and 3,4‐DCP without a lag phase. The preference for dechlorination by 2,3‐ and 2,4‐DCP adapted sediments was at the ortho chlorine. 3,4‐DCP adapted sediments, which preferentially dechlorinate at the para position of 3,4‐DCP, exhibited rapid dechlorination of the ortho and meta chlorines of all mono‐ and di‐CPs tested. Interestingly, dechlorination at the para position was not detected when 4‐CP was incubated with 3,4‐DCP adapted sediment.

Fate Of Organic Solvents In Landfill Leachates Under Simulated Field Conditions And In Anaerobic Microcosms

Municipal solid waste landfill leachates were stored in holding tanks to simulate an impoundment stabilization stage as part of a wastewater recirculation experiment. The field study was conducted over 2 consecutive years, followed by a laboratory microcosm experiment aimed at differentiating between anaerobic degradation and other processes that might be responsible for the field experiment observations. The compound CFC-113 was added to the field holding tanks and the laboratory microcosms as an indicator of anaerobic activity. The results showed that an anaerobic solution environment promotes rapid dechlorination of chlorinated solvents, but that most aromatic hydrocarbons are not degraded to the same extent. The chlorinated organic solvents contained in the leachate were found to undergo reductive dechlorination typical of anaerobic biological processes.

Fate of Organic Solvents in Landfill Leachates Under Simulated Field Conditions and in Anaerobic Microcosms

Municipal solid waste landfill leachates were stored in holding tanks to simulate an impoundment stabilization stage as part of a wastewater recirculation experiment. The field study was conducted over 2 consecutive years, followed by a laboratory microcosm experiment aimed at differentiating between anaerobic degradation and other processes that might be responsible for the field experiment observations. The compound CFC-113 was added to the field holding tanks and the laboratory microcosms as an indicator of anaerobic activity. The results showed that an anaerobic solution environment promotes rapid dechlorination of chlorinated solvents, but that most aromatic hydrocarbons are not degraded to the same extent. The chlorinated organic solvents contained in the leachate were found to undergo reductive dechlorination typical of anaerobic biological processes.

Reductive Dechlorination of Polychlorinated Biphenyls by Anaerobic Microorganisms from Sediments

Microorganisms from Hudson River sediments reductively dechlorinated most polychlorinated biphenyls (PCBs) in Aroclor 1242 under anaerobic conditions, thus demonstrating PCB dechlorination by anaerobic bacteria in the laboratory. The most rapid dechlorination was observed at the highest PCB concentration used; at 700 parts per million Aroclor, 53 percent of the total chlorine was removed in 16 weeks, and the proportion of mono- and dichlorobiphenyls increased from 9 to 88 percent. Dechlorination occurred primarily from the meta and para positions; congeners that were substituted only in the ortho position (or positions) accumulated. These dechlorination products are both less toxic and more readily degraded by aerobic bacteria. These results indicate that reductive dechlorination may be an important environmental fate of PCBs, and suggest that a sequential anaerobic-aerobic biological treatment system for PCBs may be feasible.

Dechlorination of N‐chloro poly(hexamethylene adipamide) and N‐chloro poly(ε‐caprolactam) products to the corresponding polyamides

AbstractA rapid dechlorination method of N‐chloro poly(hexamethylene adipamide) and N‐chloro poly(ε‐caprolactam) to the corresponding polyamides was studied. This method can be used for molecular weight determinations of N‐chloro polyamides by viscosimetric measurements. The dechlorination was achieved in formic acid solution by the reaction of N‐chloro polyamides with trialkyl phosphites. The reaction was exothermic and vigorous and was applied to a series of products of various degrees of N‐chlorination covering the range of 0–100%. No N—Cl was detected by iodimetric titration of the dechlorination products. The dechlorination of N‐chloro polyamides was demonstrated by infrared (IR) spectroscopy. No significant molecular weight reduction except that taking place in the N‐chlorination reaction of poly(hexamethylene adipamide) was observed.

Degradation and Metabolization of Lindane and Other Hexachloro- cyclohexane Isomers by Anaerobic and Aerobic Soil Microorganisms

Abstract Microbial Metabolization of Hexachlorocyclohexane, Anaerobic and Aerobic Microorganisms, Dechlorination of Hexachlorocyclohexane Microbial degradation of lindane or other hexachlorocyclohexane isomers has been observed to occur more rapidly in flooded than in upland soils. Experiments with a mixed bacterial flora enrich­ ed anaerobically from soils showed a rapid dechlorination and degradation of lindane. Screening studies with pure bacteria indicated that Clostridium spp. and several representatives of Bacillus spp. and Enterobacteriaceac effectively degraded lindane, while representatives of Lactobacillaceae and Propionibacterium were inactive. During degradation organic bound chlorine was released as chloride and nearly chlorine-free, partly volatile metabolites were formed. The chloride formation was promoted by the addition of glucose, pyruvate or formate. Lindane was the most easily degraded isomer, while α-and especially β-and δ-hexachlorocyclo-hexane was also, but more slowly, dechlorinated. These isomers are relatively frequently observed as environmental contaminants, their occurrence might be caused by their greater persistence or / and by an isomerization of the γ-into α-and other isomers during microbial incubation as it was discussed by several authors. Experiments, however, whether or not this isomerization can be carried out by microbes, were negative or showed that it only can occur to a very minor extent. Aerobic degradation of lindane proceeded only slowly and chiefly by formation of chlorinated aromatic compounds. One of the main intermediate metabolites seemed to be γ-pentachlorocyclo-hexene which was further transformed by the release of HCl or hydrogen and by addition of water. During anaerobic incubation, γ-tetrachlorocyclohexene intermediately occurred which was further dechlorinated to nearly chlorine-free compounds.

Synthesis of purine and pyrimidine 2′-deoxynucleosides from a 1,2-dithio sugar precursor

9-(2- S-Ethyl-2-thio- and α- D-mannofuranosyl)adenine ( 8α and 8β) were synthesized from ethyl 3,5,6-tri- O-acetyl-2- S-ethyl-1,2-dithio-α- D-mannofuranoside ( 1) by bromination followed by coupling of the resultant bromide ( 2) with 6-benzamido-(chloromercuri)purine. The 2-chloro analogues ( 10α and 10β) of 8α and 8β were obtained by way of a fusion reaction between 1,3,5,6-tetra- O-acetyl-2- S- ethyl-2-thio-α- D-mannofuranose ( 5) and 2,6-dichloropurine. Fusion of the bromide 2 with 2,4-bis(trimethylsilyloxy)pyrimidine and its 5-methyl derivative led to 1-(2- S- ethyl-2-thio-β- D-mannofuranosyl)uracil ( 16) and its thymine analogue ( 15). The action of Raney nickel led to rapid dechlorination of 10α and 10β, and all of the 2′-thio-nucleosides underwent desulfurization to give the corresponding 2′-deoxynucleosides. Sequential periodate oxidation-borohydride reduction converted the hexofuranosyl nucleosides into their pentofuranosyl analogues. Thus prepared were 9-(2-deoxy-α-and β- D- arabino-hexofuranosyl)adenine ( 11α and 11β) and their 2-deoxy- D- threo-pentofuranosyl counterparts ( 6α and 2′-deoxy-3′-epiadenosine, 6β), and 1-(2-deoxy- β- D- arabino-hexofuranosyl)-thymine ( 17) and -uracil ( 18) and their 2-deoxy- D- threo-pentofuranosyl counterparts (3′-epithymidine, 21, and 2′-deoxy-3′-epiuridine, 20). Detailed n.m.r.-spectral correlations are described for the series, and various derivatives of the nucleosides are reported.