• Korean Journal of Microbiology
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• v.32 no.1
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• pp.84-90
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• 1994

Kinetic parameters of various substrates and inhibitors were measured to elucidate the binding requirements of the active site of intracellular adenosine deaminase (ADA) in Aspergillus oryzae. 3'-Deoxyadenosine was the best substrate according to the value of relative kcat/$K_m$. Purine riboside was found to be the strongest inhibitor with the $K_i$ value of $3.7{\times}10^{-5}$M. Adenine acted neither as a substrate nor as an inhibitor, suggesting the presence of ribose at N-9 of adenosine was crucial to binding. ADA also catalyzed the dechlorination of 6-chloropurine riboside, generating inosine and chloride ions. Substrate specificity of 6-chloropurine riboside was 0.86% of adenosine. Purine riboside, a competitive inhibitor of ADA, inhibit the dechlorination with similar $K_i$ value, suggesting that the same binding site was involved in deamination and dechlorination. Among the sulfhydryl group reagents, mercurials, pchloromercuribenzoate (PCMB), mersalyl acid and $HgCl_2$ inactivated the enzyme. Mersalyl acid-inactivated ADA was reactivated by thiol reagents, but PCMB-inactivated enzyme was not. When ADA was treated with the mercurial reagents, the inhibition constants and inhibition patterns were determined. Each inhibition was competitive with substrate. The $K_i$ values of these mercurial reagents were lower in 10 mM phosphate buffer than in 100 mM phosphate buffer, showing phosphate dependency.

• Analytical Science and Technology
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• v.8 no.4
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• pp.821-827
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• 1995

Polychlorodibenzo-p-dioxins(PCDDs) have been prepared by microsacale pyrolysis of trichlorophenates. During the pyrolysis reaction, dechlorinated dibenzo-p-dioxins were also formed by the thermolysis of PCDDs. The dechlorination pathways of PCDDs were suggested in this reaction. The identification of these products was performed using capillary column gas chromatography-mass spectrometry.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.10a
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• pp.83-96
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• 2005

PVC is the thermoplastic offering excellent material properties. PVC is used in wide variety of applications, however, it causes environmental problems when it is discarded because of its high chlorine content. Since dechlorination reaction of PVC is taking place relatively low temperature compared to the pyrolysis temperature of plastics, study on the dechlorination reaction has been carried out as a pre-treatment process. Twin screw reactor which shows excellent mixing capabilities is employed. Experimental variables are first and second reactor temperature, PVC content in mixed plastics, viscosity of mixed plastics, feeding rate, rotational speed of the second reactor. Over 90% of dechlorination rate can be obtained under proper operation conditions. Chlorine gas evolved from reactor is absorbed in water and can be recovered as a hydrochloric acid. Analysis had been done on chlorine flows by taking material balance over reactor.

• Journal of Soil and Groundwater Environment
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• v.15 no.6
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• pp.114-121
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• 2010

Oxygen sensitivity and substrate requirement have been known as possible reasons for the intricate growth of Dehalococcoides spp. and limiting factors of for routinely applying bioaugmentation using anaerobic Dehalococcoides-containing microbes for remediating chlorinated organic compounds. To explore the effect of the short-term exposure of the short-term exposure of oxygen on Dehalococcoides capability, dechlorination performance, and hydrogen production fermentation from formate, an anaerobic reductive dechlorination mixed-culture (Evanite culture) including dehalococcoides spp. was in this study. In the results, once the mixed-culture were exposed to oxygen, trichloroethylene (TCE) degradation rate decreased and it was not fully recovered even addition of excess formate for 40 days. In contrast, hydrogen was continuously produced by hydrogen-fermentation process even under oxygen presence. The results indicate that although the oxygen-exposed cells cannot completely dechlorinate TCE to ethylene (ETH), hydrogen fermentation process was not affected by oxygen presence. These results suggest that dechlorinating microbes may more sensitive to oxygen than fermenting microbes, and monitoring dechlorinators activity may be critical to achieve an successful remediation of a TCE contaminated-aquifer through bioaugmentation using Dehalococcoides spp..

• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.487-493
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• 2006

Reductive dechlorination of chlorophenols by nickel coated iron was investigated to understand the feasibility of using Ni/Fe for the in situ remediation of contaminated groundwater. Zero Valent Iron(ZVI) was amended with Ni(II) ions to form bimetal(Ni/Fe). Dechlorination of five chlorophenol compounds and formation of intermediates were examined using Ni/Fe. Rate constant for each reaction pathway was quantified by the numerical integration of a series of differential rate equation. Experimental results showed that the sequence of hydrodechlorination rate constant was in the order of 2-CP>4-CP>2,4-DCP>2,4,6-TCP>2,6-DCP. The hydrodechlorination pathways for the conversion of each chlorophenol compound involves a full dechlorination to phenol via both concerted and stepwise mechanisms. Reaction pathways and corresponding kinetic rate constants were suggested based on the experiments and numerical simulations.

• Journal of Soil and Groundwater Environment
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• v.17 no.1
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• pp.33-41
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• 2012

Nanoscale zero-valent iron (nZVI) has recently received much attention for remediation of soil and groundwater contaminated with trichloroethylene (TCE). But there have been many debates on the toxic or inhibitory effects of nZVI on the environment. The objective of this study was to investigate the effects of nZVI on the activity of Geobacter lovleyi and to determine the potent effect of combination of abiotic and biotic treatment of TCE dechlorination. TCE degradation efficiencies of Geobacter lovleyi along with nZVI were more increased than those when nZVI was solely used. The amount of total microbial protein was increased in the presence of nZVI and hydrogen evolved from nZVI was consumed as electron donor by Geobacter lovleyi. In addition, dechlorination of TCE to cis-DCE by Geobacter lovleyi along with nZVI in respiking of exogenous of TCE shows that the reactivity of Geobacter lovleyi was also maintained. These results suggest that the application of Geobacter lovleyi along with nZVI for the dehalorination is beneficial for the enhancement of TCE degradation rate and reactivity of Geobacter lovleyi.

• Membrane and Water Treatment
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• v.13 no.2
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• pp.85-95
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• 2022

Tetrachloroethylene (PCE) and trichloroethylene (TCE), critical pollutants to human health and groundwater ecosystems, are managed by groundwater quality standards (GQS) in South Korea. However, there are no GQSs for their by-products, such as cis-dichloroethylene (DCE) and vinyl chloride (VC) produced through the dechlorination process of PCE and TCE. Therefore, in this study, we monitored PCE, TCE, cis-DCE, and VC in 111 national groundwater wells for three years (2016 to 2018) to evaluate their distributions, a biological dechlorination possibility, and human risk assessment. The detection frequency of them was 30.2% for PCE, 45.1% for TCE, 43.9% for cis-DCE and 13.4% for VC. The four chlorinated compounds were commonly detected in 21 out of 111 wells. In the results of statistical analysis with 21 wells data, DO and ORP also had a negative correlation with four organic chlorinated compounds, while EC and sulfate has a positive correlation with the compounds. This indicates that the 21 wells were relatively met with suitable environments for a biological dechlorination reaction compared to the other wells. Finally, cis-DCE had a non-carcinogenic risk of 10^-1 and the carcinogenic risk of VC was 10^-6 or higher. Through this study, the distribution status of the four chlorinated compounds in groundwater in South Korea and the necessity of preparing plans to manage cis-DCE and VC were confirmed.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.1
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• pp.45-53
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• 2012

The metal chloride wastes from a pyrochemical process to recover uranium and transuranic elements has been considered as a problematic waste difficult to apply to a conventional solidification method due to the high volatility and low compatibility with silicate glass. In this study, a dechlorination approach to treat LiCl-KCl waste for final disposal was adapted. In this study, a $SiO_2-Al_2O_3-P_2O_5$ (SAP) inorganic composite as a dechlorination agent was prepared by a conventional sol-gel process. By using a series of SAPs, the dechlorination behavior and consolidation of reaction products were investigated. Different from LiCl waste, the dechlorination reaction occurred mainly at two temperature ranges. The thermogravimetric test indicated that the first reaction range was about $400^{\circ}C$ for LiCl and the second was about $700^{\circ}C$ for KCl. The SAP 1071 (Si/Al/P=1/0.75/1 in molar) was found to be the most favorable SAP as a dechlorination agent under given conditions. The consolidation test revealed that the bulk shape and the densification of consolidated forms depended on the SAP/Salt ratios. The leaching test by PCT-A method was performed to evaluate the durability of consolidated forms. This study provided the basic information on the dechlorination approach. Based on the experimental results, the dechlorination method using a $SiO_2-Al_2O_3-P_2O_5$ (SAP) could be considered as one of alternatives for the immobilization of waste salt.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.2
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• pp.55-65
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• 2003

The combined effect of bioaugmentation of dechlorinating bacterial cultures and addition of iron powder($Fe^0$ on reductive dechlorination of tetrachloroethylene(PCE) and other chlorinated ethylenes in a artificially contaminated soil slurry(60micromoles PCE/kg soil). Two different anaerobic bacterial cultures, a pure bacterial culture of Desulfitobacterium sp. strain Y-51 capable of dechlorinating PCE to cis-1,2-dechloroethylene(cis-DCE) and the other enrichment culture PE-1 capable of dechlorinating PCE completely to ethylene, were used for the bioaugmentation test. Both treatments introduced with the strain Y-51 and PE-1 culture (3mg dry cell weight/kg soil) showed conversion of PCE to cis-DCE within 40days. The treatments added with $Fe^0$(0.1-1.0%) alone to the soil slurry resulted in extended PCE dechlorination to ethylene and ethane and the dechlorination rate depended on the amount of $Fe^0$ added. The combined use of the bacterial cultures with $Fe^0$(0.1-1.0%)) showed the higher PCE dechlorination rate than the separated application and the pattern of PCE dechlorination and end-product formation was different from those of the separated application. When 0.1% of $Fe^0$ was added with the cultures, the treatments with the strain Y-51 and $Fe^0$ resulted in cis-DCE accumulation from PCE dechlorination, but the treatment with the enrichment culture and $Fe^0$ showed the more extended dechlorination via cis-DCE. These results suggested that the combined application of and the bactrial culture, specially the complete dechlorinating enrichment culture, is practically effective for bioremediation of PCE contaminated soil.

• Resources Recycling
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• v.9 no.5
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• pp.22-27
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• 2000

Iron oxide produced form the pickling process at the cold rolling mill in iron & steelmaking industry, use for raw material of electronic an colorant product. Recently, decreasing of the chlorine content in iron oxide is demanded at the market. In this study, under the field test of the spray roaster and the screw conveyer for dechlorination, the experiments of the chlorine content in iron oxide were investigated. From the results of experiment, the chlorine content in iron oxide can be reduced to 1,100 ppm from the spray roaster and, 383 ppm from the screw conveyer.