Enhanced reductive dechlorination of tetrachloroethene during reduction of cobalamin (III) by nano-mackinawite

Amir, Amnorzahira; Lee, Woojin

doi:10.1016/j.jhazmat.2012.08.017

Cited by 23 publications

(26 citation statements)

References 41 publications

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“…For example, Lee and Batchelor reported the reductive degradation of chlorinated ethylenes (tetrachloroethylene (PCE), trichloroethylene (TCE), cis-dichloroethylene, and vinyl chloride) by pyrite, magnetite, and green rust. 8 Additionally, Amir and Lee 9 demonstrated an enhanced reactivity of nanomackinwite for PCE, and Choi et al 10 reported the reductive dechlorination of carbon tetrachloride (CT) and 1,1,1-trichloroethane by iron sulfide.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Studies of the Dechlorination Mechanism of Carbon Tetrachloride on a Vivianite Ferrous Phosphate Surface

et al. 2015

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International audienceChlorinated organics are the principal and most frequently found contaminants in soil and groundwater, generating significant environmental problems. Over the past several decades, Fe-containing minerals naturally occurring in aquatic and terrestrial environments have been used as natural electron donors, which can effectively dechlorinate a variety of chlorinated organics. However, a full understanding of the reaction mechanism of the dechlorination pathway cannot be obtained by experimental investigations alone, due to the immeasurability of chemical species formed over a short reaction time. In this report, we describe experiments and density functional theory (DFT) calculations carried out to investigate the complex reduction pathway of carbon tetrachloride (CT) on a vivianite (Fe(II)3(PO4)2·8H2O) surface. Our results indicate that chloroform (HCCl3) and formate are the primary transformation products. The experimental results reveal that the reduction kinetics of CCl4 can be dramatically accelerated as the pH is increased from 3 to 11. On the basis of the DFT calculations, we found that HCCl3 can be formed by (•)CCl3 and :CCl3(-)* on a deprotonated vivianite surface (an adsorbate on vivianite is denoted using an asterisk). In addition, :CCl3(-)* can be nonreductively dechlorinated to form :CCl2* followed by sequential nucleophilic attack by OH(-)*, resulting in the formation of :CCl(OH)* and :C(OH)2*, which are responsible for production of CO and formate, respectively. The results obtained from this study can facilitate the modeling of systems of other halogenated species and minerals, which will provide fundamental insight into their corresponding reaction mechanisms.[on SciFinder (R)

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Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Studies of the Dechlorination Mechanism of Carbon Tetrachloride on a Vivianite Ferrous Phosphate Surface

et al. 2015

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“…29,30 Reduction from Co 3+ to Co 2+ can easily occur because reduction potential of Co(III/II) (ΔE: 0.20 eV) is thermodynamically favorable. 14,15,29 Although further reduction from Co 2+ to Co + would be unfavorable due to its negative reduction potential (ΔE: −0.61 eV), our results showed that an intermediate having more reduced Co than Co 2+ can be formed at high concentration of S 2− environment. A previous study reported that a stabilized 3d z 2 orbital of Co in the intermediate can raise the reduction potential and bring the further reduction of Co 2+ to Co + .…”

Section: Materials Andmentioning

confidence: 68%

“…Transformations of PCE to TCE, ethene (PCE → TCE → ethene), and to 1,3-butadiene (PCE → 1,3-butadiene) indicate that hydrogenolysis and isomerization were also involved in the reductive transformation of PCE by Cbl(III)−S 2− in nFeS suspension. 15,35 The trichlorovinyl radical and hexachloro-1,3-butadiene may form as unstable intermediates during the degradation of PCE by cobalamin complexes with nFeS and S 2− . 35 Previous studies have also shown that PCE was transformed to butenes and chlorobutadiene by titanium(III) citrate with Cbl(III)−CN via isomerization, 35 confirming that the isomerization path was a potential transformation pathway in the nFeS suspension with Cbl(III)− S 2− .…”

Section: Materials Andmentioning

confidence: 99%

Reductive Transformation of Tetrachloroethene Catalyzed by Sulfide–Cobalamin in Nano-Mackinawite Suspension

Kyung

Amir

Choi

et al. 2015

Ind. Eng. Chem. Res.

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In this study, we demonstrated the reductive substitution of aquo−cobalamin(III) (Cbl(III)−H 2 O) by sulfide− cobalamin(III) (Cbl(III)−S 2− ) in the presence of S 2− . Cbl(III)−H 2 O was transformed to Cbl(III)−S 2− via ligand substitution of H 2 O by S 2− at its axial position, due to the weakness of the bond strength of cobalt with H 2 O. Cbl(III)−S 2− was reduced to sulfide−cobalamin(II) and partially further to sulfide−cobalamin(I) as the concentration of S 2− increased from 0.1 to 5.0 mM. In the presence of nanomackinawite (nFeS), Cbl(III)−S 2− species were fully adsorbed onto the nFeS surface, and its reactivity was enhanced by the reactive surface chemical species. The dechlorination kinetic rate constant of tetrachloroethene by Cbl(III)−S 2− in nFeS suspension (k nFeS−Cbl(III)−S 2− = 0.008 ± 0.001 h −1 ) was 4 times greater than that by Cbl(III)−H 2 O, showing a potential role for ≡S 2− −Cbl(II) as a more effective electron transfer mediator than ≡S n 2− −Cbl(II) and ≡OH−Cbl(II). The experimental results provide fundamental knowledge on potential biogeochemical reactions relevant to interactions between S 2− and bacterial coenzyme in nFeS suspension, which can significantly enhance reductive dechlorination of chlorinated compounds in contaminated sites.

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“…The percentage was calculated by dividing a molar concentration of each product at 6 hr by initial molar concentration of PCE. Total carbon mass of PCE accounted for 90.0% at last sampling time and unrevealed portion (10.0%) may be transformed to other hydrocarbons such as 1,3-butadiene (Amir and Lee 2012). Chlorinated products such as TCE, 1,1-DCE, cis-DCE, trans-DCE, and VC were not observed in 6 hr.…”

Section: Analytical Proceduresmentioning

confidence: 95%

Reductive dechlorination of tetrachloroethylene by bimetallic catalysts on hematite in the presence of hydrogen gas

Choi¹,

Lee²,

Lee³

2014

Advances in environmental research

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Among the combination of 4 different second metals and 3 different noble metals, Ni 10%-Pd 1%/hematite (Ni(10)-Pd(1)/H) showed best tetrachloroethylene (PCE) removal (75.8%) and production of non-toxic products (39.8%) in closed batch reactors under an anaerobic condition. The effect of environmental factors (pH, contents of Ni and Pd in catalyst, and hydrogen gas concentration) on the reductive dechlorination of PCE by Pd-Ni/hematite catalysts was investigated. PCE was degraded less at the condition of Ni(5)/H (13.7%) than at the same condition with Ni(10)/H (20.6%). Removals of PCE were rarely influenced by the experimental condition of different Pd amounts (Pd(1)/H and Pd(3)/H). Acidic to neutral pH conditions were favorable to the degradation of PCE, compared to the alkaline condition (pH 10). Increasing Ni contents from 1 to 10% increased the PCE removal to 89.8% in 6 hr. However, the removal decreased to 74.2% at Ni content of 20%. Meanwhile, increasing Pd contents to 6% showed no difference in PCE removal at Pd content of more than 1%. Increasing H 2 concentration increased the removal of PCE until 4% H 2 which was maximumly applied in this study. Chlorinated products such as trichloroethylene, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, and vinyl chloride were not observed while PCE was transformed to acetylene (24%), ethylene (5%), and ethane (11%) by Ni(10)-Pd(1)/H catalyst in 6 hr.

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Enhanced reductive dechlorination of tetrachloroethene during reduction of cobalamin (III) by nano-mackinawite

Cited by 23 publications

References 41 publications

Theoretical and Experimental Studies of the Dechlorination Mechanism of Carbon Tetrachloride on a Vivianite Ferrous Phosphate Surface

Theoretical and Experimental Studies of the Dechlorination Mechanism of Carbon Tetrachloride on a Vivianite Ferrous Phosphate Surface

Reductive Transformation of Tetrachloroethene Catalyzed by Sulfide–Cobalamin in Nano-Mackinawite Suspension

Reductive dechlorination of tetrachloroethylene by bimetallic catalysts on hematite in the presence of hydrogen gas

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