Electrochemical reduction and anaerobic degradation of lindane

Beland, Frederick A.; So, Farwell; Ae, Robocker; Rd, Geer

doi:10.1021/jf60206a019

Cited by 57 publications

(35 citation statements)

References 14 publications

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“…5. This is also in agreement with the results reported by Beland et al [11] for electrochemical and anaerobic processes of lindane dechlorination to benzene, where only ␥-BTC was observed as intermediate, i.e. the loss of adjacent chlorines occurred.…”

Section: Mechanism Of Lindane Dechlorination Over Metal Catalysts Witsupporting

confidence: 93%

“…The latter is more selective and can be carried out under mild conditions in the presence of a phase-transfer (PT) catalyst and an aqueous base [9,10]. Electrochemical [11] and bacterial [11][12][13] processes of HCH or lindane degradation are known and afford benzene. Lindane decomposition via sonochemical [14] or gamma ray [15] induced dechlorination/destruction has also been demonstrated.…”

Section: Introductionmentioning

confidence: 99%

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Dechlorination of lindane in the multiphase catalytic reduction system with Pd/C, Pt/C and Raney-Ni

Zinovyev

Shinkova

Perosa

et al. 2004

Applied Catalysis B: Environmental

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Dechlorination of ␥-hexachlorocyclohexane (lindane) is carried out in the multiphase catalytic system, composed by isooctane and aqueous KOH phases, a phase transfer agent (Aliquat 336) and a metal catalyst, e.g. 5% Pd/C, 5% Pt/C, or Raney-Ni. At 50• C and atmospheric pressure the full conversion of lindane to 1,2,4-tricholorobenzene (1,2,4-TCB) is achieved in 5-10 min via the base assisted dehydrochlorination, followed by the metal catalyzed hydrodechlorination with hydrogen to benzene. Aqueous KOH and Aliquat 336 strongly affect the reaction: if present together they co-promote both dehydrochlorination and hydrodechlorination steps; if KOH is absent, the reaction is forced to follow a different catalytic pathway, which involves a removal of a pair of chlorines at every reaction step by zerovalent metal followed by reduction of metal with hydrogen. This is proven by the formation of 3,4,5,6-tetrachlorocyclohex-1-ene and 5,6-dichlorocyclohexa-1,3-diene as intermediates in the reaction over Raney-Ni, and by the absence of TCBs in the reactions on all the catalysts studied. The final yield of benzene via this pathway can be achieved in shorter times than in a system with KOH. The presence of Aliquat 336 in the isooctane-water system produces a 10-fold rate increase, the presence of alkaline water is also important since it avoids catalyst poisoning by neutralizing the hydrochloric acid formed.

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Section: Mechanism Of Lindane Dechlorination Over Metal Catalysts Witsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Dechlorination of lindane in the multiphase catalytic reduction system with Pd/C, Pt/C and Raney-Ni

Zinovyev

Shinkova

Perosa

et al. 2004

Applied Catalysis B: Environmental

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“…Chlorobenzene is then produced by a dehydrochlorination reaction. Several reports confirmed the presence of ␥-TCCH as an intermediate in the anaerobic degradation of ␥-HCH (11,58,64,126). The degradation of ␥-HCH also results in the formation of small amounts of trichlorinated benzenes and benzene itself (64).…”

Section: Anaerobic Degradationmentioning

confidence: 86%

“…3) (11,21,98,126,137). Ohisa et al (126) proposed that the degradation proceeds through two dichloroeliminations, resulting in the formation of ␥-3,4,5,6-tetrachloro-1-cyclohexene (␥-TCCH) and, subsequently, 5,6-dichlorocyclohexa-1,2-diene.…”

Section: Anaerobic Degradationmentioning

confidence: 99%

Biochemistry of Microbial Degradation of Hexachlorocyclohexane and Prospects for Bioremediation

Lal

Pandey

Sharma

et al. 2010

Microbiol Mol Biol Rev

350

338

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SUMMARY Lindane, the γ-isomer of hexachlorocyclohexane (HCH), is a potent insecticide. Purified lindane or unpurified mixtures of this and α-, β-, and δ-isomers of HCH were widely used as commercial insecticides in the last half of the 20th century. Large dumps of unused HCH isomers now constitute a major hazard because of their long residence times in soil and high nontarget toxicities. The major pathway for the aerobic degradation of HCH isomers in soil is the Lin pathway, and variants of this pathway will degrade all four of the HCH isomers although only slowly. Sequence differences in the primary LinA and LinB enzymes in the pathway play a key role in determining their ability to degrade the different isomers. LinA is a dehydrochlorinase, but little is known of its biochemistry. LinB is a hydrolytic dechlorinase that has been heterologously expressed and crystallized, and there is some understanding of the sequence-structure-function relationships underlying its substrate specificity and kinetics, although there are also some significant anomalies. The kinetics of some LinB variants are reported to be slow even for their preferred isomers. It is important to develop a better understanding of the biochemistries of the LinA and LinB variants and to use that knowledge to build better variants, because field trials of some bioremediation strategies based on the Lin pathway have yielded promising results but would not yet achieve economic levels of remediation.

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“…Reductive dehalogenation appears to be the main pathway and converts DDT to DDD (Glass, 1972;Zoro et al, 1974), DTE to DDE (Beland et al, 1974), and lindane to benzene (Beland et al, 1976) under reducing conditions. Anaerobic degradation of toxaphene mixtures has also been reported in anaerobic soils (Parr and Smith, 1976) and in salt marsh sediments (Williams and Bidleman, 1978).…”

Section: Oa Bmentioning

confidence: 99%

The role of colloidal organic matter in the marine geochemistry of PCBs

Brownawell¹

1986

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WITHDRAWN AD -sT~i~Bñ~c i~tZ4-2-ABSTRACT Polychlorinated biphenyls (PCBs) were used as model hydrophobic organic compounds (HOC) to study physical-chemical processes which affect the speciation and fate of HOC in coastal environments. The focus of this study is on the sorption of PCBs with colloidal organic matter in seawater, and the influence of this process on the distribution of PCBs in coastal sediments. Laboratory and field experiments were used to make quantitative estimates of PCB-organic matter sorption, and to test predictions of three-phase equilibrium models.A static headspace partitioning method was developed to measure the sorption of several individual chlorobiphenyls with colloidal organic matter enriched from coastal seawater by hollow fiber ultrafiltration. This technique directly measured the dissolved phase fugacity of PCBs in experimental bottles, and avoided uncertain separation techniques often used in isolating various chemical phases. Colloidal organic carbon normalized partition coefficients (Koc) were determined from linear sorption isotherms, and increased from 1.9 x 10' (L/Kg) for 2,4'-dichlorobiphenyl to 3.5 x 10 s for 2,2',3,4,5'-pentachlorobiphenyl. Sorption tended to increase with increasing octanol-water partition coefficients (Kow) of the sorbate, and values of Koc were within a range of those reported in other experimental sorption studies with sediments and dissolved humic substances. Experimental partitioning results support the hypothesis that HOC-organic colloid sorption is similar to HOC sorption by sediment organic matter.PCBs were measured in the interstitial waters and sediments of three box cores obtained from New Bedford Harbor and Buzzards Bay, Massachusetts. The three sites studied had a wide range of sediment PCB concentrations, and reducing conditions provided environments containing high concentrations of colloidal organic matter. Dissolved organic carbon (DOC) and total sediment organic carbon (TOC) were measured in two cores to test the role of organic matter on the observed partitioning of PCBs. PCB concentrations, particularly those of less soluble chlorobiphenyls, were highly elevated in interstitial waters compared to water column concentrations at all three sites. The measured apparent distribution coefficients (K'd) of individual chlorobiphenyls did not increase with hydrophobicity (Kow) and indicate that a large fraction of PCBs in interstitial waters must be sorbed to organic colloids. A three-phase equilibrium sorption model, in which dissolved PCBs are in a dynamic equilibrium with colloidal and sediment organic matter, accounts for many aspects of the field data. There is good agreement of observed partitioning at New Bedford Station 67 and Buzzards Bay Station M with model calculations based on predictions derived from laboratory experiments of HOC sorption with sediments and organic colloids, but model calculations underpredict K'd at Station 84 in New Bedford Harbor.-3-The sediment-interstitial water results were contrasted with a study of PCB pa...

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Electrochemical reduction and anaerobic degradation of lindane

Cited by 57 publications

References 14 publications

Dechlorination of lindane in the multiphase catalytic reduction system with Pd/C, Pt/C and Raney-Ni

Dechlorination of lindane in the multiphase catalytic reduction system with Pd/C, Pt/C and Raney-Ni

Biochemistry of Microbial Degradation of Hexachlorocyclohexane and Prospects for Bioremediation

The role of colloidal organic matter in the marine geochemistry of PCBs

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