• Title/Summary/Keyword: dechlorination

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Anaerobic dechlorinating enrichment culture on tetrachloroethene (PCE) (PCE 탈염소화를 위한 혐기성배양)

  • Kim, Byung-Hyuk;Baek, Kyung-Hwa;Sung, Youl-Boong;Choi, Gang-Kook;Cho, Dae-Hyun;Oh, Hee-Mock;Kim, Hee-Sik
    • Proceedings of KOSOMES biannual meeting
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    • 2007.11a
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    • pp.185-185
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    • 2007
  • Starting at the beginning q the 20th century, increasing amounts of tetrach1oroethene (PCE) and trichloroethene (TCE)were manufactured due to the extensive use of these compounds in industry, in the military, and in private households, mainly as nonflammable solvents. This widespread use, along with careless handling and storage, are among the most serious contaminants of soil, sediment and groundwater. Highly chlorinated ethenes are typically not degraded through oxygenation by aerobic bacteria Since complete reductive dechlorination of PCE and TCE to ethene (ETH) has been observed in anaerobic enrichment culture, anaerobic dehalorespiring bacteria have received increased attention in the last decade. Under anaerobic conditions, these compounds con be reductively dehalogenated to less-chlorinated ethenes or innocuous ethene by microorganism through dehalorespiration. We have been studying anaerobic enrichment culture which used lactate as the electron donor for reductive dechlorination of PCE to ETH the anaerobic mixed microbial culture was enriched from the sediment sample taken from site contaminated with PCE. PCE was consistently and completely converted to ethene. In addition, the accumulation of intermediate products such as 1,2-ds-dichloroethene (cis-DCE) and vinyl chloride (VC) was observed in the anaerobic mixed microbial culture. the established dechlorinating enrichment culture was analyzed by DGGE using primers specific to DefrJ1ococcoides 16S rRNA gene sequences. In conclusion, we established the PCE dechlorinating enrichment culture and confirmed the existence of Dehalococcoides in an enrichment culture.

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Microbial degradation of the persistent pollutant TCAB : (II) -Degradation of TCAB by isolated microorganisms- (난분해성(難分解性) 공해물질(公害物質) TCAB의 미생물(微生物)에 의(依)한 분해(分解) : (II) -분리(分離) 균주(菌株)에 의(依)한 TCAB의 분해(分解)-)

  • Lee, Jae-Koo;Ihm, Yang-Bin;Cho, Yong-Gyun;Kyung, Kee-Sung;Oh, Kyeong-Seok;Kim, Hak-Nam
    • Applied Biological Chemistry
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    • v.34 no.4
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    • pp.299-306
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    • 1991
  • When $[U-^{14}C]$ 3,3', 4,4'-tetrachloroazobenzene$([U-^{14}C]\;TCAB)$ was added to the $MM_2$ medium as a sole carbon source for the isolated microorganisms and incubated, some radioactive metabolites were detected by autoradiography. No $^{14}CO_2$ was evolved from $[U-^{14}C]\;TCAB$ which was added as a sole carbon source to an organic matter-free soil inoculated by the isolates, wetted with the $MM_2$ salt medium, and incubated at $30^{\circ}C$. One of the metabolites in pure culture of Achromobacter group VD, which was isolated and identified, was tentatively identified as a compound of m/z 250 by means of GC/MS. The possible pathways for its formation are thought to include dechlorination from the TCAB structure, hydroxylation, ortho fission of the two benzene rings, and reduction of the resulting carboxyl group.

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Effects of Calcium on TCE Degradation Reaction in Cement/Fe(II) and Hematite/Fe(II) Systems (시멘트/Fe(II) 및 hematite/Fe(II) 시스템의 TCE 분해반응 시 Ca 성분의 영향)

  • Kim, Hong-Seok;Hwang, Kyung-Yup;Ahn, Jun-Young;Yi, Jou-Young;Hwang, In-Seong
    • Journal of Soil and Groundwater Environment
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    • v.16 no.1
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    • pp.82-90
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    • 2011
  • Reactive reductants of cement/Fe(II) systems in dechlorinating chlorinated hydrocarbons have not been identified. The previous studies showed that a hematite/CaO/Fe(II) system had TCE degradation characteristics similar to those of cement/Fe(II) systems with regard to degradation kinetics and that lime (CaO) plays an important role in enhancing the reactivity for TCE dechlorination. The current study shows identified the formation of gypsum ($CaSO_4$) in the hematite/CaO/$FeSO_4$ system through the XRD analysis. The amounts of the gypsum increased with increment of the initial CaO dose. However, when CaO in the hematite/CaO/$FeSO_4$ system was replaced with gypsum, TCE degradation was not observed. Ca-removed Portland cement extracts (CPCX) in combination with $FeSO_4(CPCX/FeSO_4)$ showed no TCE degradation. On the other hands, the Portland cement extracts (PCX) in the presence of $FeSO_4(PCX/FeSO_4)$ and CPCX/CaO/$FeSO_4$ systems degraded 0.2 mM TCE within 5 days, indicating that CaO also played an important role dechlorination reactions in the systems. The pseudo-first-order rate constants (k) of the CPCX/CaO/$FeSO_4$ systems were 0.20, 0.24, and 0.72 $day^{-1}$, when the CaO dosages were 25, 50 and 75 g/L, respectively. The XRD analyses showed identified the common peaks having the d-values of 3.02, 2.27, and 1.87 in the reaction systems that showed TCE degradation. However, it was not possible to clearly identify the crystalline minerals having the three peaks from the references in JCPDS cards. This study reveals that the reactive agents in the cement/Fe(II) and the hematite/Fe(II) systems are likely to be those containing CaO and Fe(II).

Formation of Tetra-Chlorinated Dibenzo-p-dioxins and Their Thermal Decomposition Products from Pyrolysis Reaction of Tri-Chlorophenates

  • 홍종기;박종세;김강진
    • Bulletin of the Korean Chemical Society
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    • v.17 no.4
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    • pp.334-338
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    • 1996
  • Tetra-chlorodibenzo-p-dioxins (tetra-CDDs) were prepared by microscale pyrolysis of trichlorophenates. During the pyrolysis reaction, tri-, di-, and mono-CDDs were also formed by the thermolysis of tetra-CDDs. The dechlorination pathways of tetra-CDDs were suggested for this reaction. The identification of these products was performed with capillary column gas chromatography-mass spectrometry.

Photosensitization of Trichlorobenzenes(TCBs) in Aqueous Solution: III. Photoproducts with Nitrite ($\textrm{NO}_2$) and Triethylamine(TEA)

  • Kim, Jae H.
    • Environmental Analysis Health and Toxicology
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    • v.11 no.3_4
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    • pp.33-44
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    • 1996
  • Photolysis of TCBs in aqueous solutions of sodium nitrite and triethylamine (TEA) at neutral pH has been investigated. TCBs yielded trichloronitrobenzenes(TCNBs) as primary photoproducts, and their corresponding trichlorophenols (TCPs) via two types of reaction, one, nitration, and the other, by direct hydroxylation with OH radical. Isomerized products and TCBs were also identified. Photosensitization with TEA resulted in the formation of small yields of dichlorobenzenes(DCBs) by reductive dechlorination of TCBs.

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Preliminary Experiments for the Remediation of Trichloroethene-Contaminated Groundwater Using Direct-Current and Zero-Valent Iron (0가 철과 직류전원을 이용한 TCE 오염 지하수의 정화기법 예비조사)

  • Moon, Ji-Won;Moon, Hi-Soo;Roh, Yul;Lee, Suk-Young;Song, Yun-Goo
    • Economic and Environmental Geology
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    • v.34 no.3
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    • pp.307-313
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    • 2001
  • Reactive medium including zero-valent metals such as zero-valent iron ($Fe^0$) degrades chlorinated solvents as a contaminant plume flows through the treatment medium. Although the Feo based reactive barrier has been demonstnlted to be a cost effective for trichloroethenc (TCE)-contaminaled plume remediation, current approach is limited by low process eftlciency and uncertain, effective life of the medium. The objective of this study is to develop an enhanced treatment method of TeE-contaminated groundwater using Feo and direct current. The bench-scale test using flow-through $Fe^0$ reactor column confirmed that the application of direct current with $Fe^0$ is highly effective in enhancing the rate of TeE dechlorination. The dechlorination mechanism appears to be reductive, with the electrons supplied by the iron oxidation and external power supply serving as the additional source of electrons.

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Treatment of hazardous chemicals by Nanoscale Iron powder (나노크기 철 분말을 이용한 난분해성 유해화합물질의 처리)

  • 최승희;장윤영;황경엽;김지형
    • Journal of Korea Soil Environment Society
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    • v.4 no.3
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    • pp.85-93
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    • 1999
  • The destruction of hazardous chemicals such as chlorinated organic compounds(COCs) and nitroaromatic compounds(NACs) by zero-valent iron powder is one of the latest innovative technologies. In this paper. the rapid dechlorination of chlorinated compounds as well as transformation of nitro functional group to amine functional group in the nitroaromatic compounds using synthesized zero-valent iron powder with nanoscale were studied in anaerobic batch system. Nanoscale iron, characterized by high surface area to mass ratios(31.4$\textrm{m}^2$/g) and high reactivity, could quickly reacts with compounds such as TCE, chloroform, nitrobenzene, nitrotoluene, dinitrobenzene and dinitrotoluene, at concentration of 10mg/L in aqueous solution at room temperature and pressure. In this study, the TCE was dechlorinated to ethane and chloroform to methane and nitro groups in NACs were transformed to amino groups in less than 30min. These results indicated that this chemical method using nanoscale iron powder has the high potential for the remediation of soils and groundwater contaminated with hazardous toxic chemicals including chlorinated organic compounds and nitro aromatic compounds.

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Cloning and Expression of pcbAB Genes from Pseudomonas sp. DJ-12 in Escherichia coli (Pseudomonas sp. DJ-12 pcbAB 유전자의 Escherichia coli에서의 클로닝 및 발현)

  • 한재진;성태경;김치경
    • Korean Journal of Microbiology
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    • v.31 no.2
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    • pp.129-134
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    • 1993
  • The pchAB genes of Pseudomonas sp. DJ-12 produce the enzymes of 4-chlorobipheny] (4CB) dioxygenase and dihydrodiol dehydrogenase which act on the first and second steps in degradation of 4CB and biphenyl. The genes were cloned in E coli XLI-Blue. The pcbAB genes of about 2.2 kb in size were contained in the pCUlO1 hybrid plasmid in the cloned cell of CUIOI. The genes were found to have their own promoter and three restriction sites for HindlII. 2,3-dihydroxybiphenyl was detected by the resting cell assay, as the metabolite transformed from biphenyl by the cloned cell of CUIOI. This means that the pcbAB genes are well expressed in E. coli. But dechlorination was unlikely involved in the pchAB gene expression but was believed to occur by functioning on 4CBA produced after ring-cleavage of 4CB.

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Transformation Characteristics of Chlorinated Aliphatic Hydrocarbon (CAH) Mixtures in a Two-Stage Column: 1st Chemical Column Packed with Zinc Natural Ore and 2nd Biological Column Stimulated with Propane-Oxidizing Microorganisms (아연 광석과 프로판산화 미생물을 이용한 이단 고정상 반응기에서의 염소계 지방족 탄화수소 혼합물 분해 특성)

  • Son, Bong-han;Kim, Nam-hee;Hong, Kwang-pyo;Yun, Jun-ki;Lee, Chae-young;Kwon, Soo-youl;Kim, Young
    • Journal of Korean Society on Water Environment
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    • v.23 no.5
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    • pp.723-730
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    • 2007
  • This study was conducted to develop a combined method for remediating a Chlorinated Aliphatic Hydrocarbons (CAHs) mixtures-contaminated aquifer. The process is consist of two processes. A chemical process (1st) using natural zinc ores for reducing higher concentrations of CAH mixtures to the level at which biological process is feasible; and A biological process (2nd) using aerobic cometabolism for treating lower concentration of CAH mixtures (less than 1 mg/L). Natural zinc ore showed relatively high transformation capacity, average dehalogenation percentage, and the best economic efficiency in previously our study. To evaluate the feasibility of the process, we operated two columns in series (that is, chemical and biological columns). In the first column filled with natural zinc ore and sand, CAH mixtures were effectively transformed with more than 95% efficiency, the efficiency depends on the Empty Bed Contact Time (EBCT) and the mass of zinc ore packed. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) analysis were performed to make sure whether natural zinc ore played an key role in the dechlorination of the CAH mixtures. The characteristics of zinc metal surface changed after exposure to CAHs due to oxidation of $Zn^0$ to $Zn^{2+}$. In the biological column injecting propane, DO and effluent of the chemical column, only 1,1,1-TCA was cometabolically transformed. Consequently, the combined process would be effective to remediate an aquifer contaminated with high concentrations of CAH mixtures.

Quantitative Distribution of Created Voids by Applying General Flame and DC Short-circuit Current to 2.5 mm2 HIV (2.5 mm2 HIV에 일반화염 및 DC 단락 전류를 인가하여 생성된 기공의 정량적 분포 해석)

  • Kim, Seung-Sam;Choi, Chung-Seog
    • Journal of the Korean Society of Safety
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    • v.28 no.4
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    • pp.38-42
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    • 2013
  • This study performed the quantitative distribution analysis of created voids to an insulator when applying general flame and DC short-circuit current to 2.5 $mm^2$ HIV (600 V Grade Heat-Resistant Polyvinyl Chloride Insulated Wires). The diameter of cross-section of HIV normal product and the radius of conductor were measured to be 3.3 mm and 1.8 mm. The exterior of HIV exposed to general flame showed severe carbonization and its interior exhibited voids created by dechlorination reaction. This study observed the characteristics that, when the shortcircuit current applied for 2 seconds from a DC 12 V lead battery, the conductor and neighboring insulator were melted, causing the insulator adhering to the conductor. On average, 87 voids were created on 10 mm of the HIV. The average diameter of voids was 0.25 mm. In addition, it was found that, when the short-circuit current applied for 4 seconds, the interior of insulator in contact with conductor severely carbonized and showed exfoliation phenomenon. On average, 47 voids were created, with more voids at the bottom. The average diameter of voids was 0.20 mm. When the short-circuit current for 6 seconds, most parts of upper part of conductor was carbonized, 20 voids were created. The average diameter of voids was measured to be 0.24 mm. It could be seen that the created voids received little influence by the type of energy source and the number of created voids was reduced as the energy supply time increased.