• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.387-391
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• 1997

냉각재중의 방사능을 띤 성분 중에는 이온교환기에서 제거가 가능한 이온성분과 함께 필터에 의해서 주로 제거되는 입자성 물질로 존재한다. 운전중의 냉각재내 방사성 부식생성물의 물리적 조성 분포 측정 결과에 따르면 90%이상이 0.45$mu extrm{m}$필터에 의해 제거되는 입자성 물질로 구성되어 있다. 이로 인해 새수지 충전후 얼마 사용하지 않은 탈염기의 제염계수가 탈염기에서 완벽한 제거가 어려운 입자성 부식생성물로 인해 10이하를 나타낼 수 있다. 1차계통에 쓰이는 수지의 성능검사를 위해 사용하고 있는 현재의 제염계수 측정법은 다음과 같은 두가지 이유로 완벽하지 않음을 알 수 있다. 첫째, 냉각재중의 방사능을 띤 성분중에는 이온교환기에서 제거가 가능한 이온성분과 함께 필터에 의해 제거되는 입자성 물질도 함께 존재하므로 탈염기의 제염계수 측정 절차는 입자성 물질을 배제한 후 측정해야 하며, 특히 수치 교체를 결정하기 위한 제염계수 측정시에는 여과된 여액으로 방사능 농도를 측정하는 것이 바람직하다. 둘째 운전중인 냉각재의 시료중에는 핵분열 수율이 높고 핵연료봉 손상부위로 유출이 용이한 불활성 기체핵종들이 많이 존재하며, 탈염기 후단에서 채취한 시료중에도 많이 존재하고, 시료 이송과 방사능 측정동안의 짧은 시간동안에도 계속 붕괴반응함으로서 새로 생긴 핵종으로 인해 마치 탈염기의 제거능이 낮은 것으로 오판될 수 있다. 이러한 측정 오차인자를 고려하여야 1차계통 탈염기의 교환능력을 정확히 판정할 수 있다.

• Journal of Conservation Science
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• v.31 no.2
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• pp.95-104
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• 2015

Excavated archaeological cast iron objects in improper storage are quickly corroded and disintegrated into block and powder finally. Hence desalination treatment which is a way of removing internal corrosive factors, especially chloride ion, is an important process. But desalination is often omitted or objects are dehydrated by alcohol because the destruction of objects could occur during desalting. Although current desalting methods mostly use an aqueous alkali solution, $OH^-$ ions of water could accelerate corrosion and broaden internal cracks cause of high surface tension. Therefore this study experimented desalting using ethyl alcohol, which is low surface tension, to investigate an effect of desalination. As a result, desalting using ethyl alcohol showed the similar or more effective results of desalting using water. In addition, as aspects of desalting safety, ethyl alcohol desalting method was smaller destruction of objects and extraction of Fe from the objects than the aqueous alkali solution. However, this study explored the possibility of desalting methods using organic solvent in fieldwork, so the results would provide basic date for making the safe and effective desalting method for archaeological cast iron objects through further experiments.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.5
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• pp.304-311
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• 2012

Chlorinated ethylenes such as perchloroethylene (PCE) and trichloroethylene (TCE) are widely used as industrial solvents and degreasing agents. Because of improper handling, these highly toxic chlorinated ethylenes have been often detected from contaminated soils and groundwater. Biological PCE dechlorination activities were tested in bacterial cultures inoculated with 10 different environmental samples from sediments, sludges, soils, and groundwater. Of these, the sediment using culture (SE 2) was selected and used for establishing an efficient PCE dechlorinating enrichment culture since it showed the highest activity of dechlorination. The cathode chamber of bioelectrochemical system (BES) was inoculated with the enrichment culture and the system with a cathode polarized at -500 mV (Vs Ag/AgCl) was operated under fed-batch mode. PCE was dechlorinated to ethylene via TCE, cis-dichloroethylene, and vinyl chloride. Microbial community analysis with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) showed that the microbial community in the enrichment culture was significantly changed during the bio-electrochemical PCE dechlorination in the BES. The communities of suspended-growth bacteria and attached-growth bacteria on the cathode surface are also quite different from each other, indicating that there were some differences in their mechanisms receiving electrons from electrode for PCE dechlorination. Further detailed research to investigate electron transfer mechanism would make the bioelctrochemical dechlorination technique greatly useful for bioremediation of soil and groundwater contaminated with chlorinated ethylenes.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.125-131
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• 2009

Reductive dechlorination of polychlorinated dibenzo-p-dioxins (PCDDs) and its toxicity change were predicted by the linear free energy relationship (LFER) model to assess the zero-valent iron (ZVI) and anaerobic dechlorinating bacteria (ADB) as electron donors in PCDDs dechlorination. Reductive dechlorination of PCDDs involves 256 reactions linking 76 congeners with highly variable toxicities, so is challenging to assess the overall effect of this process on the environmental impact of PCDD contamination. The Gibbs free energies of PCDDs in aqueous solution were updated to density functional theory (DFT) calculation level from thermodynamic results of literatures. All of dechlorination kinetics of PCDDs was evaluated from the linear correlation between the experimental dechlorination kinetics of PCDDs and the calculated thermodynamics of PCDDs. As a result, it was predicted that over 100 years would be taken for the complete dechlorination of octachlorinated dibenzo-p-dioxin (OCDD) to non-chlorinated compound (dibenzo-p-dioxin, DD), and the toxic equivalent quantity (TEQ) of PCDDs could increase to 10 times larger from initial TEQ with the dechlorination process. The results imply that the single reductive dechlorination using ZVI or ADB is not suitable for the treatment strategy of PCDDs contaminated soil, sediment and fly ash. This LFER approach is applicable for the prediction of dechlorination process for organohalogen compounds and for the assessment of electron donating system for treatment strategies.

• Journal of the Korean GEO-environmental Society
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• v.13 no.9
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• pp.53-59
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• 2012

This study investigated characteristics of decomposition of tetrabutoxysilane (TBOS) as a slow release substrate (SRS) and on effect of TBOS decompostion compounds (acetate and butylate) for anaerobic dechlorination of trichloroethylene (TCE). In the batch experiment, TCE, cis-dichloroethene (cis-DCE), 1-butanol and TBOS were analysed by GC/FID and acetate and butylate were measured by HPLC. 1M of TBOS transferred and accumulated 4M of 1-butanol by abiotically hydrolysis reaction. The hydrolysis rate was in a range of 0.186 ${\mu}M/day$. On other hand, 1-butanol fermented to butyrate and acetate with indigenous culture from natural sediments. This results showed that TBOS could be used a slow release substrate in the natural sites. The dechlorinated potential of TCE with acetate and butyrate was increased with a decreasing initial TCE concentrations. In addition, first order coefficients of dechlorination with acetate as electron donor was higher then that with butyrate. It is because that dechlorination of Geobacter lovleyi was affected by substrate affinity, biodegradability and microbial acclimation on various substrates. However, dechlorinated potential of Geobacter lovleyi was decreased with accumulation cis-DCE in the anaerobic decholoronation process. The overall results indicated that SRS with Geobacter lovleyi might be a promising material for enhancing dechlorination of TCE on natural site and cis-DCE should be treated by ZVI as reductive material or by coexisting other dechlorinated bacteria.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.292-299
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• 2006

Batch experiments were performed to evaluate the effects of the electron donor dosage and the initial biomass on the reductive dechlorination of perchloroethene(PCE) with benzoate as an electron donor. When benzoate was added less than the theoretical requirement for dechlorination(electron donor/acceptor ratio=0.5 and 1), the dechlorination efficiency increased from 71% to 94.3% with the increase in benzoate dosage, but the fraction of electron equivalent utilized for dechlorination decreased from 92.7% to 79.6%. Methane production was observed when the hydrogen concentration was higher than the threshold value(10 nM) after PCE and trichloroethene (TCE) were reduced to cis-1,2-dichloroethene(cDCE). When benzoate was added more than the theoretical requirement, the residual hydrogen converted into methane after the completion of dechlorination. The increase in the seeding biomass shortened the lag time for dechlorination, but it did not affect the maximum dechlorination rate as it was mainly governed by the benzoate fermentation rate. When the seeding biomass concentration was high, active dechlorination during the early period increased dechlorination efficiency while decreasing methane production.

• Journal of Conservation Science
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• v.37 no.6
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• pp.821-830
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• 2021

The weapons excavated from the de-militarized zones (DMZ) of Korea are vulnerable to corrosion due to the immediate and drastic environmental change. Especially, the chloride ions (Cl^-) in iron weapons cause active corrosion and require removal. In this study, conservation treatment and de-salination was performed for the discovered weapons from excavation sites of soldiers killed in action during the Korean War. Furthermore, an attempt was made to prepare the most stable plan for conservation treatment through the comparative study of soaking weapons in distilled water without chemicals and in a solution of sodium (SSC) at different temperatures. In the preliminarily experiments, the comparison of the eluted Cl^- ions according to different conditions of de-salination showed that the highest number of ions were detected from the de-salination with SSC at a temperature of 100℃, and its duration was much smaller, i.e., 1~2 weeks. Accordingly, for the parts from the guns and rifles amongst other objects, a six-time de-salination was conducted in the SSC solution for 8 hours at 100℃ and subsequently, for 16 hours at room temperature during which the distilled water and SSC were exchanged every week. However, in the case of a loaded rifle, the de-salination was not conducted, considering the risk that the high temperature and pressure by impregnation in vacuum could cause an explosion

• Membrane Journal
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• v.26 no.3
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• pp.229-237
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• 2016

We prepared heterogeneous ion exchange membranes (hetero-IEMs) for the application of membrane capacitive deionization (MCDI). Hetero-IEMs were fabricated by compressing the mixture of ion exchange resin powders and liner low density polyethylene (LLDPE). Characterization and MCDI desalination experiments were carried for the fabricated membranes. Electrical resistance of membrane decreased and water content increased with increasing the resin content in the hetero-IEMs. However, transport number indicating permselectivity of membrane was similar with that of commercial homogenesous ion exchange membrane. The results of MCDI desalination experiments showed that the adsorption amount for hetero-IEM was about 90% of that of homogeneous membrane due to the high electrical resistance of hetero-IEM. Although desalination performance of hetero-IEM decreased compared with homogeneous membrane, it was thought to be applicable to MCDI because of simple preparation and low price.

• 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.

• Korean Journal of Microbiology
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• v.45 no.2
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• pp.140-147
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• 2009

In this study, anaerobic enrichment cultivation was performed with the sediments from the Gimpo and Inchon areas. Lactate as an electron donor and PCE as an electron acceptor was injected into the serum bottle with an anaerobic medium. After the incubation of 8 weeks, the reductive dechlorination of PCE was observed in 7 sites among 16 sites (43%). Three enrichment cultures showed completely dechlorination of PCE to ethene, while four enrichment culture showed transformation of PCE to cis-DCE. The bacterial community structure was analyzed by PCR-DGGE. Dechlorinating bacteria were detected by species-specific primers. The dominant species in seven anaerobic enrichments were found to belong to the genus of Dehalococcoides sp. and Geobacter sp., and Dehalobacter sp.