• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.2
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• pp.187-196
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• 2021

Chemical equilibrium calculations for multicomponent aqueous systems involving the reductive dissolution of magnetite (Fe₃O₄) with oxalic acid (H₂C₂O₄) were performed using the HSC Chemistry® version 9. They were conducted with an aqueous solution model based on the Pitzer's approach of one molality aqueous solution. The change in the amounts and activity coefficients of species and ions involved in the reactions as well as the solution pH at equilibrium was calculated while changing the amounts of raw materials (Fe₃O₄ and H₂C₂O₄) and the system temperature from 25℃ to 125℃. In particular, the conditions under which Fe₃O₄ is completely dissolved at high temperatures were determined by varying the raw amount of H₂C₂O₄ and the temperature for a given raw amount of Fe₃O₄ fed into the aqueous solution. When the raw amount of H₂C₂O₄ added was small for a given raw amount of Fe₃O₄, no undissolved Fe₃O₄ was present in the solution and the pH of the solution increased significantly. The formation of ferrous oxalate complex (FeC₂O₄) was observed. The equilibrium amount of FeC₂O₄ decreased as the raw amount of H₂C₂O₄ increased.

• The Journal of the Korea Contents Association
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• v.14 no.12
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• pp.845-853
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• 2014

In this study, we measured the dose reaching the OSLD dosimeter by using the regular lead apron, and air gap apron through 3 experiments, and researched the reductive effect of air gap apron on exposure dose based on the 140 keV gamma ray radiating from $^{99m}technetium$, which is the most commonly used in nuclear medicine. As a result, when the gap between the dosimeter and 0.2mm lead plate is 0 Cm, the average value of 10 dosimeters was 0.515 mSv, and when the gap between the dosimeter and lead plate is 20 Cm, the average value of 10 dosimeters was 0.138 mSv, which shows reductive effect of dose as much as 0.388 mSv. When the gap between the dosimeter and 0.5mm lead plate is 0 Cm, the average value of 10 dosimeters was 0.296 mSv, and when the gap between the dosimeter and lead plate is 20 Cm, the average value of 10 dosimeters was 0.075 mSv, which shows reductive effect of dose as much as 0.221 mSv. As we check the cumulative dosage for 3 days, the lead apron without air layer shows average 0.239 mSv, and the air gap apron shows 0.176 mSv, which is actually reduced by 0.062 mSv. As we check the cumulative dosage for a month, the lead apron without air layer shows 0.59 mSv, and the air gap apron shows 0.54 mSv, which is reduced by 0.05 mSv.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.5
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• pp.1099-1106
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• 1999

Effects of dietary carotenoids were investigated on metabolism of the carotenoids, and body pigmen tation in oily bittering, Acheilognathus koreensis. Two weeks later after depletion,oily bitterings were fed the diets supplemented with either lutein, cynthiaxanthin and astaxathin for 4 weeks. Carotenoids distributed to and metabolized in integument were analyed. The carotenoid isolated from the integument of wild oily bittering, composed of 47.2% zeaxanthin, 11.4% lutein epoxide, 11.0% diatoxanthin, 9.7% lutein and 8.3% zeaxanthin epoxide. Meanwhile, two weeks later after depletion, the carotenoid composed of 29.9% crytoxanthin, 19.3% zeaxanthin, 13.2% lutein epoxide, 12.0% diatoxanthin and 8.8% zeaxanthin epoxide. These indicated that zeaxanthin, diatoxanthin, lutein epoxide and zeaxanthin epoxide were actively metabolized in oily bittering, compared to that of other fresh water fish. Total carotenoid content in the integument of wild oily bittering and oily bittering depleted for two weeks was found to be 1.72mg% and 2.08mg%, respectively. Two weeks later after treatment of experimental diet, total carotenoids content was increased to 2.23mg% in lutein, 2.36mg% in cynthiaxanthin and 2.49mg% in astaxanthin supplemented group, which were relatively higher than 2.10mg% in control group. Meanwhile, 4 weeks later, total ca rotenoids content was decreased to 1.76mg% in control, 1.95mg% in lutein, 1.74mg% in cynthiaxanthin and 1.72mg% in astaxanthin supplemented groups. These result indicate that dietary carotenoids were rapidly accumulated and then metabolized to certain metabolites shortly after feeding. Body pigmentation effects of the carotenoids due to accumulation of carotenoids in the integument of oily bittering was the most effectively shown in the astaxanthin supplemented group, followed by cynthiaxanthin and lutein supplemented groups. In the integument of oily bittering, dietary carotenoids were presumably biotrans formed via either oxidative or reductive pathways as presumed the variation of total carotenoid content and carotenoid composition in all experimental groups. The lutein was oxidized either to astaxanthin via doradexanthin and doradexanthin, or to zeaxanthin epoxide via zeaxanthin by oxidative pathway. Cynthiaxanthin was converted either to diatoxanthin and zeaxanthin by reductive pathway and then to zeaxanthin epoxide by oxidative pathway, or it was converted to astaxanthin via diatoxanthin, zeaxan thin and doradexanthin by oxidative pathway. Astaxanthin was converted to doradexanthin and zeaxanthin by reductive pathway and then to zeaxanthin epoxide by oxidative pathway. These results suggest that, oxidative pathway of carotenoids was major metabolic pathway along with reductive path way in fresh water fish.

• Journal of Soil and Groundwater Environment
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• v.12 no.6
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• pp.38-45
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• 2007

Trichloroethylene (TCE) is a representative dense non-aqueous phase liquid (DNAPL) and has contaminated substance environments including soil and groundwater due to leakage and careless. DNPAL, has been treated by surfactant-enhanced aquifer remediation (SEAR). After application of SEAR, groundwater contains still surfactant as well as little amount of residual TCE. Permeable reactive barrier using zero-valent iron (ZW) is a very effective technology to treat the residual TCE in groundwater. In this study, the effect of the residual surfactant on the reductive dechlorination of residual TCE was investigated using ZVI. Mixed surfactant composed of nonioinic surfactant and cationic surfactant was used as a residual surfactant because of toxicity and enhancement of dechlorination rate. Structure of surfactant affected significantly the decrhlorination rate of TCE. Mixed surfactant system with relatively short polyethylene oxide (PEO) chain in nonionic surfactant, cationic surfactant did not affect TCE dechlorination rate. However, mixed surfactant system with relatively long PEO chain in nonionic surfactant shows that TCE dechlorination rate was significantly dependent on fraction of cationic surfactant and HLB of nonionic surfactant. Cationic surfactant with trimethyl ammonium group enhanced reductive dechlorination rate compared to that surfactant with pyridinium group.

• 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.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1421-1423
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• 2010

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.3117-3119
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• 2011

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.2085-2087
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• 2010

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.500-502
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• 2010

• Journal of the Korean Chemical Society
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• v.40 no.1
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• pp.96-99
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• 1996