• Journal of the Korean Applied Science and Technology
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• v.24 no.4
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• pp.436-443
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• 2007

Anaerobic reductive dehalogenation of perchloroethene (PCE) was studied with lactate as the electron donor in a continuously stirred tank reactor (CSTR) inoculated with a mixed culture previously shown to dehalogenate vinyl chloride (VC). cis-1,2- dichloroethene (cDCE) was the dominant intermediate at relatively long cell retention times (>56 days) and the electron acceptor to electron donor molar ratio (PCE:lactate) of 1:2. cDCE was transformed to VC completely at the PCE to lactate molar ratio of 1:4, and the final products of PCE dehalogenation were VC (80%) and ethene (20%). VC dehalogenation was inhibited by cDCE dehalogenation. Propionate produced from the fermentation of lactate might be used as electron donor for the dehalogenation. Batch experiments were performed to evaluate the effects of increased hydrogen, VC, and trichloroethene (TCE) on VC dehalogenation which is the rate-limiting step in PCE dehalogenation The addition of TCE increased the VC dehalogenaiton rate more than an increase in the $H_2$ concentration, which suggests that the introduction of TCE induces the production of an enzyme that can comtabolize VC.

• Environmental Engineering Research
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• v.23 no.4
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• pp.345-353
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• 2018

This paper summarizes results of research on the electrochemical (EC) degradation of disinfection by-products (DBPs) and iodine-containing contrast media (ICMs), with the focus on EC reductive dehalogenation. The efficiency of EC dehalogenation of DBPs increases with the number of halogen atoms in an individual DBP species. EC reductive cleavage of bromine from parent DBPs is faster than that of chlorine. EC data and quantum chemical modeling indicate that the EC reduction of iodine-containing DBPs (I-DBPs) is characterized by the formation of active iodine that reacts with the organic substrate. The occurrence of ICMs has attracted attention due to their association with the generation of I-DBPs. Indirect EC oxidation of ICMs using anodes that produce reactive oxygen species can result in a complete degradation of these compounds yet I-DBPs are formed in the process. Reductive EC deiodination of ICMs is rapid and its overall rate is diffusion-controlled yet I-DBPs are also produced in this reaction. Further progress in practically feasible EC methods to remove DBPs, ICMs and other trace-level organic contaminants requires the development of novel electrocatalytic materials, elimination of mass transfer limitations via innovative design of 3D electrodes and EC reactors, and further progress in the understanding of intrinsic mechanisms of EC reactions of DBPs and TrOC at EC interfaces.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.1074-1076
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• 2011

• Environmental Engineering Research
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• v.25 no.2
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• pp.197-204
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• 2020

A number of different nanoscale zero-valent iron (nZVI) materials have been prepared and compared depending on the desired properties for the particular application, but different physicochemical properties of this prepared nZVI make it difficult to universally compare and standardize them to the same scale. In this study, we aimed to demonstrate a simple microplate-based colorimetric assay using 4-chlorophenol as an indicator with respect to the remediation of real treatment targets, such as trichloroethylene (TCE), 1,1,1-trichloroethane (TCA), and atrazine. Effect of nickel contents on 4-chlorophenol reduction was successfully investigated by the miniaturized colorimetric assay. In the same manner, the effect of nickel contents on dehalogenation of TCE, TCA, and atrazine was investigated and the pseudo-first-order kinetic constants were compared with the results for 4-chlorophenol. The similar pattern could be observed between 4-chlorophenol reduction obtained by colorimetric assay and TCE, TCA, atrazine reduction obtained by a traditional chromatographic method. The reaction kinetics does not match perfectly, but the degree of reaction can be estimated. Therefore, the colorimetric assay can be a useful and simple screening tool to determine nZVI reactivity toward halogenated organics before it is applied to a particular remediation site.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 1998.10a
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• pp.153-156
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• 1998

• Bulletin of the Korean Chemical Society
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• v.20 no.8
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• pp.865-866
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• 1999

• Bulletin of the Korean Chemical Society
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• v.21 no.2
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• pp.211-214
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• 2000

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.117-121
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• 2002

A numerical model that describes the reductive dechlorination of tetrachloroethene(PCE) to ethene via cis-dichloroethene(CDCE) was developed. The model included two separated dehalogenator groups : one for PCE transformation to cDCE via TCE and the other for cDCE dehalogenation to ethene via VC, competitive inhibition between different chloroethene electron accepters, and competition for H$_2$ between dechlorination and methanogens. Model simulations suggest first, that PCE dechlorinators are better competitive with methanogens than cDCE dechlorinators. Second, not only the initial relative population size of dehalogenators and H$_2$-utilizing methanogens but also electron donor delivery strategies used greatly affects the degree of dehalogenation. As a result, all of factors in the above must be considered in order to achieve economical and successful bioremediation of contaminated soil and groundwater with chlorinated solvents.

• Bulletin of the Korean Chemical Society
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• v.15 no.10
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• pp.845-849
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• 1994

Tetracarbonylhydridoferrate, $HFe(CO)^-_4$, generated by the reaction of $Fe(CO)_5$ with alkaline solution, is a good reducing agent for mono-dehalogenation of gem-dihalocyclopropanes. It also acts as a good reducing catalyst under phase transfer reaction conditions. 1,1-Dibromo-2-phenylcyclopropane and 1,1-dichloro-2-phenylcyclopropane were reduced to the corresponding mono-dehalogenated products in excellent yields. Thermodynamically stable trans-l-bromo-2-phenyl cyclopropane was formed as the major product over the cis-isomer, trans/cis=3/2. The 1-bromo-2-phenyl cyclopropane radical intermediate was formed by single electron transfer from $HFe(CO)^-_4$. Dissociation of bromide anion, followed abstraction of hydrogen radical from alcoholic solvent would lead to the formation of the stable trans-isomer. The further mechanistic aspects were discussed.

• Journal of Marine Bioscience and Biotechnology
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• v.6 no.2
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• pp.76-83
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• 2014

Bacteria associated with marine sponges seemed to be concerned in halogenation/dehalogenation process of natural compounds. In the present study, the effect of hexabromobenzene (HBB) on the community structure of bacteria associated with a marine sponge Axinella sp. from Chuuk State under anaerobic condition was investigated. Regardless of 100 ppm HBB, most of detected microorganisms displayed high similarity with clones reported from coral or sponges. Amongst, Desulfovibrio marinisediminis like clones were dominant. Clones affiliated with Lentisphaerae and Fusibacter paucivorans (Clostridia) were detected at the conditions without HBB but clones affiliated with Vallitalea guaymasensis (Clostridia) increased its proportion with HBB. From these results and previous reports clones affiliated with D. marinisediminis and V. guaymasensis seemed to be concerned in halogenation/dehalogenation process.