• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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• pp.441-448
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• 2016

Heavy metal removal study is conducted from synthetic waste water by reduction and oxidation(redox) reaction of Cu-Zn metal alloy and adsorption reaction of aluminium silicate. Heavy metal whose ionization tendency is smaller than zinc are reducted in an aqueous solution, and the concentration of ionized zinc is reduced by adsorption reaction. The average diameter of metal alloy micro fiber is about $200{\mu}m$, and the surface area is wide enough to get equilibrium in a single cycle treatment. A single cycle treatment of redox reaction of Cu-Zn metal alloy, could remove 100.0 % of Cr(III), 98.0 % of Hg, 92.0 % of Sn and 91.4 % of Cu respectively. An ionization tendency of chromium is very close to zinc, but removal efficiency of chromium by redox reaction is significant. This result shows that trivalent chromium ion is expected to generate hydroxide precipitation with $OH^-$ ion generated by redox reaction. Zinc ion generated by redox reaction is readily removed by adsorption reaction of aluminium silicate in a single cycle treatment. Other heavy metal components which are not perfectly removed by redox reaction also showed very high removal efficiency of 98.0 % or more by adsorption reaction. Aluminium ion is not increased by adsorption reaction of aluminium silicate. That means heavy metal ion removal mechanism by adsorption reaction is turned out to be not an ion exchange reaction, but an adsorption reaction.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.67-71
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• 2013

$FeCl_3$ has been used as an etchant for metal etching such as Fe, Cu, and Al. In the process of metal etching, $Fe^{3+}$ is reducted to $Fe^{2+}$ and the etching rate becomes slow and etching efficiency decreased. Waste $FeCl_3$ etchant needs to be regenerated because of its toxicity and treatment cost. In this work, HCl was initially mixed with the waste $FeCl_3$ and then, strong oxidants, such as $O_2$ and $H_2O_2$, were added into the mixed solution to regenerate the waste etchant. During successive etching and regeneration processes, oxygen-reduction potential (ORP) was continuously measured and the relationship between ORP and etching capability was investigated. Regenerated etchant using a two vol% HCl of the total etchant volume and a very small amount of $H_2O_2$ was very effective in recovering etching capability. During the etching-regeneration process, the same oxygen-reduction potential variation cannot be repeated every cycle since concentrations of $Fe^{2+}$ and $Fe^{3+}$ ions were continuously changed. It suggested that the control of etching-regeneration process based on the etching time becomes more efficient than that of the process based on oxygen reduction potential changes.

• Clean Technology
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• v.27 no.2
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• pp.152-159
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• 2021

Volatile organic compounds (VOCs) occur in indoor and outdoor industrial and urban areas and cause environmental problems. Malodorous VOCs, along with aesthetic discomfort, can have a serious effect on the human body. Compared with the existing method of reducing malodorous VOCs, a wet scrubbing method using an electrolytic oxidant has the advantage of reducing pollutants and regenerating oxidants. This study investigated the optimal conditions for producing OCl^-, a chlorine-oxidant. Experiments were conducted by changing the type of anode and cathode electrode, the type of electrolyte, the concentration of electrolytes, and the current density. With Ti/IrO₂ as the anode electrode and Ti as the cathode electrode, OClproduction was highest and most stable. Although OCl^- production was similar with the use of KCl or NaCl, NaCl is preferable because it is cheap and easy to obtain. The effect of NaCl concentration and current density was examined, and the OCl^- production rate and concentration were highest at 0.75 M NaCl and 0.03 A cm^-2. However, considering the cost of electric power, OCl^- production under the conditions of 1.00 M NaCl and 0.01 A cm^-2 was most effective among the conditions examined. It is desirable to produce OCl^- by adjusting the current density in accordance with the concentration and characteristics of pollutants.

• Journal of Life Science
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• v.18 no.2
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• pp.220-227
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• 2008

To clarify the antioxidation effect of the various solvent fractionation of Tetragonia tetragoniodes which has been known to superior plants for the traditional prevention and treatment of stomach-related diseases, total polyphenol and flavonoid contents, vitamin E content, the elimination activity of a DPPH free radical and superoxide anion, inhibition activity of the superoxide generation, reducing power and metal chelating effects were estimated. The contents of the polyphenol compounds were highest in the DCM and EA fractionation, and the content of flavonoid was high in the order of HX and EA fractionation. The vitamin E content showed high in the order of the HX and DCM fractionation among solvent fractions. $IC_{50}$ for the elimination effect of a DPPH radical were estimated as 554.25 and $394.96{\mu}g/ml$ in the DCM and EA fractions, respectively. These values were higher than that of BHT $784.7{\mu}g/ml$ widely used in antioxidation effect. The inhibition activity of the superoxide generation using the T. tetragoniodes solvent fractions represented the effects similar to that of ${\alpha}$-tocopherol known to prevent the lipoprotein oxidation, but lower consequences than that of the phenol-resins, BHT and BHA, respectively. In the antioxidation activity derived by the reducing capability, the EA fractionation in a 1.5 mg/ml concentration showed higher than that of ${\alpha}$-tocopherol.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.213-216
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• 2009

WGS(Water Gas Shift)반응은 일산화탄소(CO)를 이산화탄소($CO_2$)로 전환하는 반응으로 일체형 수소생산시스템의 실현을 위한 고순도 수소생산에 있어서 중요한 단계이다. WGS 반응은 열역학적 평형을 고려하여 고온전이반응(HTS: High Temperature Shift)과 저온전이반응(LTS: Low Temperature Shift) 두 단계 반응으로 진행된다. 두 단계 공정의 통합을 위해 낮은 온도에서 높은 활성을 갖는 WGS 반응용 촉매 개발이 필요하다. 최근 낮은 온도에서 높은 활성을 갖는 귀금속 촉매에 다양한 담체를 적용시킨 연구가 활발히 진행되고 있다. 선행 연구 결과, Ce-$ZrO_2$ 구조는 Ce/Zr 비에 따라 다양한 특성 변화를 관찰하였다. 따라서 낮은 온도에서 높은 활성을 갖는 WGS 반응용 촉매 제조를 위해 환원성 담체인 $CeZrO_2$에 Pt 을 담지시켜 성능을 평가하였다. 제조된 모든 담체는 공침법(Co-precipitation)으로 제조 하였으며 $500^{\circ}C$에서 6시간 소성하였다. 제조된 담체에 백금(Pt)을 함침법(Incipient Wetness Impregnate)으로 담지시켰다. 특성분석은 BET를 이용하여 표면적을 측정하였다. 촉매 반응 실험조건은 $200^{\circ}C{\sim}400^{\circ}C$ 온도범위에서 기체공간속도(GHSV: Gas Hourly Space Velocity) 45,000 ml/$h{\cdot}g-cat$ 으로 혼합가스($H_2$:60%, $N_2$:20%,$CH_4$:1%,CO:9%,$CO_2$:10%)를 흘려 반응 후 배출되는 가스를 Micro-Gas Chromatography 를 이용하여 측정하였다.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.249-256
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• 2006

Catalytic combustion of toluene was investigated on the Cu-Mn oxide catalysts prepared by the impregnation(Imp) and the deposition-precipitation(DP) methods. The mixing of copper and manganese has been found to enhance the activity of catalysts. It is then found that catalytic efficiency of the Cu-Mn oxide catalyst prepared by the DP method on combustion of toluene is much higher than that of the Cu-Mn oxide catalyst prepared by Imp method with the same chemical composition. The catalyst prepared by the deposition-precipitation method observed no change of toluene conversion at time on stream during 10 days and at the addition of water vapor. On the basis of catalyst characterization data, it has been suggested that the catalysts prepared by the DP method showed uniform distribution and smaller particle size on the surface of catalyst and then enhanced reduction capability of catalysts. Therefore, we think that the DP method leads on progressive capacity of catalyst and promotes stability of catalyst. It was also presumed that catalytic conversion of toluene on the Cu-Mn oxide catalyst depends on redox reaction and $Cu_{1.5}Mn_{1.5}O_4$ spinel phase acts as the major active sites of catalyst.

• Korean Journal of Food Science and Technology
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• v.53 no.6
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• pp.785-791
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• 2021

Many lactic acid bacteria (LAB) have probiotic properties that exert various health benefits. In this study, the reduction potential of nitrogen oxide compounds and ferric ions by six LAB, including Lactobacillus kimchicus, L. lactis, L. casei, L. plantarum, L. rhamnosus GG, and Leuconostoc mesenteroides were evaluated. The L. kimchicus strain produced a substantial amount of nitrite reduced from nitrate added to the media, whereas the other five LAB strains did not. L. kimchicus also showed the most potent reducing activity of ferric to ferrous ions. However, the reduction potential of the autoclaved L. kimchicus was little pronounced. The scavenging activities of viable LAB or their cell lysates against different radicals were not consistent with the potency of the LAB's reducing ability. The present results indicate that L. kimchicus has a strong reduction potential for nitrogen oxides in viable status, and that this ability can be used as a probiotic property for various health benefits.

• Journal of Food Hygiene and Safety
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• v.35 no.5
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• pp.513-520
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• 2020

Here, we evaluated the functional properties of histidine-containing low-molecular-weight (LMW) peptides obtained from tuna waste meats. As with histidine-related components composed of histidine, 1-methyl histidine and anserine, histidine-containing LMW peptides exhibited high α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging effect in a dose-dependent manner. Among the histidine-related dipeptides, anserine exhibited the highest reducing power followed by carnosine. By comparison with dipeptides, tuna extracts also showed similar reducing power and the activity was in a dose-dependent manner. In addition, the antioxidant activities of tuna extracts such as DPPH radical scavenging effect, reducing power, superoxide dismutase activities, and peroxide value of linoleic acid were affected by the various extraction methods.

• Clean Technology
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• v.21 no.2
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• pp.117-123
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• 2015

This inquiry was conducted to develop DeNOx catalyst for LNT. In order to develop appropriate catalysts, four catalysts, which do not use PGM (Platinum Group Metal), were carefully selected : Al/Co/Mn, Al/Co/Ni/Mn, Al/Co/Mn/Ca, Al/Co/Ni mixed metal oxides during preliminary experiments. Also, XRD, EDS, SEM, BET and TPD tests were carried as well to evaluate both physicochemical properties of such four catalysts. As a result of the experiment, four catalysts were composed of spinel-shaped crystals and had more than enough pore volume and size to have oxidation-reduction reaction of NOx gases. Additionally, through TPD test, all four types of catalysts were proved to possibly have an oxidation-reduction acid site and NO oxidation activities similar to commercial catalysts. Based on the results above, if we have further change in the composition components and active ingredients according to the catalysts that were chosen in this investigation, then we are more welcomed to expect to have an enhanced DeNox catalyst for LNT.

• Korean Journal of Microbiology
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• v.39 no.3
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• pp.175-180
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• 2003

Microbial Fe(III) reduction is an important factor for biogeochemical cycle in anaerobic environments, especially sediment of freshwater such as lakes, ponds and rivers. In addition, the Fe(III) reduction serves as a model for potential mechanisms for the oxidation of organic compounds and the reduction of toxic heavy metals, such as chrome or uranium. Shewanella putrefaciens DK-1 was a gram-negative, facultative anaerobic Fe(III) reducer and used ferric ion as a terminal electron acceptor for the oxidation of organic compounds to $CO_{2}$ or other oxidized metabolites. The ability of reducing activity and utilization of various electron acceptors and donors for S. putrefaciens DK-1 were investigated. S. putrefaciens DK-1 was capable of using a wide variety of electron acceptor, including $NO_{3}^{-}$, Fe(III), AQDS, and Mn(IV). However, its ability to utilize electron donors was limited. Lactate and formate were used as electron donors but acetate and toluene were not used. Fe(III) reduction of S. putrefaciens DK-l was inhibited by the presence of either $NO_{3}^{-}$ or $NO_{2}^{-}$. Further S. putrefaciens DK-1 used humic acid as an electron acceptor and humic acid was re-oxidized by nitrate. Environmental samples showing the Fe(III)-reducing activity were used to investigate effects of the limiting factors such as carbon, nitrogen and phosphorus on the Fe(III) reducing bacteria. The highest Fe (III) reducing activity was measured, when lactate as a carbon source and S. putrefaciens DK-1 as an Fe(III) reducer added in untreated sediment samples of Cheon-ho and Dae-ho reservoirs.