• Journal of the Korean Wood Science and Technology
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• 제27권4호
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• pp.65-71
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• 1999

This study was carried out to investigate the effect of xylanase pretreatment of the unbleached hardwood kraft pulp during the conventional Chlorine-Extraction- Hypochlorite (CEH) bleaching on pulp property. Optimum bleaching condition was evaluated by using Novozym produced from the fungus Humicola insolens. Also the effect of chelating agent prior to enzyme treatment was analyzed. The kappa number of enzymatic bleached pulp at the enzyme charge 10 IU/ml was slightly similar to that of bleached pulp without enzyme. By enzyme treatment, the chlorine charge in conventional CEH bleaching process of hardwood KP could be reduced by 17%, while no adverse effect on pulp yield and strength was. The optimum condition for enzyme pretreatment was 10 IU/ml xylanase charge, 3 to 4 hrs treatment, and 2% pulp consistency. In sugar composition in the enzyme pretreated pulp, arabinose and mannose were not much different, but more xylose was retained. This high content of hemicellulose in pulp seems to play an important role in pulp properties. The pulp pretreatment by chelating agent prior to enzyme treatment could improve the enzyme activity and enhance the bleaching effect at 0.2% diethylenetriamine pentaacetic acid (DTPA) charges.

• Bulletin of the Korean Chemical Society
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• 제29권7호
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• pp.1327-1331
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• 2008

Novel $CO_2$-soluble 8-hydroxyquinoline (8-HQ) chelating agents were synthesized and evaluated for solubility and metal ion extraction ability in supercritical $CO_2\;(Sc-CO_2)$. Among them, secondary amide-containing 8- HQ derivatives cannot be dispersed well into Sc-$CO_2$, but tertiary amide-containing derivatives can dissolve completely in Sc-$CO_2$ even at low CO2 pressures, perhaps owing to the predominant intermolecular interaction between the chelating agent and the $CO_2$ molecule. Based on 8-HQ chelating agent solubility data, we investigated the extraction of metal ions ($Co^{2+}$, $Cu^{2+}$, $Sr^{2+}$, $Cd^{2+}$, and $Zn^{2+}$) using two highly $CO_2$-soluble 8-HQ derivatives (4d, 4e) in Sc-$CO_2$. The extraction efficiency of tertiary amide-containing 8-HQ ligands, both fluorinated and non-fluorinated forms, was dramatically increased in the presence of diethyl amine (organic base). We suggest that diethyl amine could play an important synergistic role in the stronger metal binding ability of 8-HQ through an in situ deprotonation reaction in Sc-$CO_2$ medium.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제10권S_3호
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• pp.139-148
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• 2001

Heavy metals such as Cu, Ni, Cd, and Pb were chemically extract from the contaminated soils using the chelating agents, EDTA and DTPA. These chemical extraction have been focused on its applicability to a wide range of soils. Results of extractive efficiency for heavy metal follow the order : Cu-EDTA $\geq$ Ni-EDTA > Pb-EDTA > Cd-EDTA > Cu-DTPA> Pb-DTPA. This result is coincided with order of conditional formation constants(Kr) of metal-chelate agent. The second study involved the recovery of the metals and EDTA from complex solutions by an electromembrane process. The overall processes of regeneration, recovery, and reuse were evaluated. The electrochemical studies showed that copper could be chosen as an electrode to plate Cd, Cu, and Pb. At least 95% of 75 of EDTA and associated Cu or Pb could be recovered by the electromembrane process. Recovery of Cd by electodeposition was not possible with the copper electrode. The percent EDTA recovery is equal to the percentage of metal electroplated from the chelates.

• 한국지하수토양환경학회지:지하수토양환경
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• 제26권1호
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• pp.54-64
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• 2021

The chemical warfare agents (CWAs) have been developed for offensive or defensive purposes and used as chemical weapons in war and terrorism. The CWAs are exposed to the natural environment, transported through the water system and then eventually contaminate soil and groundwater. Therefore, effective decontamination technology to remediate CWAs are needed. The CWAs are extremely dangerous and prodution is strictly prohibited, therefore, it is difficult to use CWAs even in experimental purpose. In this study, 2,4-dichlorophenoxyacetic acid (2,4-D) was chosen as a model representative CWA because it is a simulant of anti-plant CWAs and one of the major component of agent orange. The optimum degradation conditions such as oxidant:activator ratio were determined. The effects of hydroxylamine and chelating agents such as citric acid (CA), oxalic acid (OA), malic acid (MA), and EDTA addition to increase Fe2+ activation were also investigated. Scavenger experiments using tert-butyl alcohol (TBA) and ethanol confirmed that although both sulfate (SO4•-) and hydroxyl radical (•OH) existed in Fe2+-persulfate system, sulfate radical was the predominant radical. To promote the Fe2+ activator effect, the effect of hydroxylamine as a reducing agent was investigated. In chelating agents assisted Fe2+-persulfate oxidation, the addition of 2 mM of CA and MA enhanced 2,4-D degradation. In contrast, EDTA and OA inhibited the 2,4-D removal due to steric hindrance effect.

• 생명과학회지
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• 제20권7호
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• pp.1041-1046
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• 2010

Phytoextraction은 식물을 이용하여 환경 정화하는 한 기술로서 금속으로 오염된 토양을 정화하는 것이다. 토양에 존재하는 금속의 추출을 용이 하기 위해서 현재 다양한 킬레이트가 사용되고 있다. Phytoextraction이 경제적이고 친환경적인 장점이 있지만 고농도로 오염된 지역에서는 적용이 어려운데 이는 식물이 이러한 지역에서 살아남기 어렵기 때문이며 이러한 문제점을 해결하는 것이 본 연구의 목적이다. 연구 대상의 금속으로서 알루미늄을 선택하였고, 킬레이트는 아미노산인 시스테인과 히스티딘, 작은 크기의 유기산으로서 citric acid, malic acid, succinic acid, oxalic acid, 그리고 ethylenediamine (EDA)를 선택하였으며, EDTA는 비교 대상으로 본 연구에 사용되었다. 다양한 농도의 알루미늄를 포함하는 배지에 식물을 키우면서 여러 킬레이트가 식물의 뿌리 성장에 미치는 영향을 분석하였다. 알루미늄에 의한 식물의 성장 억제는 히스티딘에 의해서 약간 완화되었으며 시스테인, citrate, malate, oxalate, 그리고 succinate는 별 다른 영향이 없었다. EDTA와 EDA는 알루미늄에 의한 식물성장 억제를 강력하게 억제하였으며 이는 알루미늄의 식물 내 흡수를 억제에 의한 것이다. 따라서 알루미늄의 식물성장억제를 강력하게 완화시켜주는 EDA는 고농도의 알루미늄으로 오염된 지역에 식물의 성장이 가능하도록 유용하게 사용될 수 있을 것이다.

• 대한화학회지
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• 제31권4호
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• pp.308-314
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• 1987

중금속 이온의 흡착, 분리 및 회수에 적합한 킬레이트제 침윤수지의 조건을 조사하기 위하여 cupferron (CP), diphenylcarbazone (DPC), salicylaldoxime (SAO), thiosalicylic acid (TSA), 및 dimethylglyoxime (DMG)등의 킬레이트제를 선택하여 Amberite XAD-7 수지에 대한 흡착성을 조사하였다. 킬레이트제-XAD-7 침윤수지들을 만들고, 각 침윤수지들에 대한 Cu(Ⅱ) 이온의 흡착, 분리 및 회수능을 비교하였다. Cu(Ⅱ) 이온에 대해서 적절한 침윤수지로는 비교적 넓은 pH 영역에서 킬레이트제의 흡착이 안정하고 Cu(Ⅱ)와 넓은 pH 범위에서 정량적인 흡착을 보이는 SAO-XAD-7과 DMG-XAD-7 침윤수지임을 알았다. SAO-XAD-7 수지를 사용하여 Cu(Ⅱ) 이온을 공존하는 Ni(Ⅱ) 이온으로부터 분리하였다. Cu(Ⅱ)이온의 최적흡착량은 SAO-XAD-7 침윤수지의 경우는 수지 1g에 대해서 $7{\times}10^{-3}mmol$이며, DMG-XAD-7의 경우는 $2{\times}10^{-3}mmol$이다. 또한 흡착된 Cu(Ⅱ)이온. 1N HCl로 용출시켜 정량적으로 회수하였다. 한편 혼합 침윤수지에서의 Cu(Ⅱ)와 Ni(Ⅱ) 이온의 선택적 흡착성을 조사하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제11권6호
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• pp.76-82
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• 2006

일반적으로 Fenton 반응 공정을 실제 오염토양에 적용하기에는 다소 무리가 있다. 그 이유로 대표적인 Fenton 반응공정인 고전적인 Fenton 반응은 낮은 pH에서 우수한 처리효율을 보이고 있기 때문이다. 또한, 철이온의 투입을 대신하여 철광석을 이용하는 Fenton-like 반응도 철광석 표면에서 hydroxyl radical을 생성하나 높은 pH에서는 다량의 수산화물과의 경쟁반응으로 인하여 그 활성이 상당히 감소되어진다. 이러한 단점을 보완하기 위하여 중성영역의 pH에서 철이온-chelating agent의 복합체를 촉매로 사용하는 modified Fenton 반응이 제시 되어지고 있다. 이 처리방식의 경우에는 다량의 철이온의 투입이 요구되어진다. 따라서, 본 실험에서는 Fenton-like 반응과 modified Fenton 반응의 효율적인 접목으로 중성영역에서의 chelating agent의 투입으로 철광석으로부터 철이온을 용출하여 복합체를 형성함으로 혼합 Fenton 공정에서 부가적인 촉매로 사용되어짐으로 오염물 처리효율을 크게 향상시킨 기법 개발을 진행하였다. 2,4,6-Trinitrotoluene은 본 실험에서 오염원으로 사용하였으며, chelating agent에 의해 용출된 철이온이 약 0.1 mM 이상일 경우 Fenton-like 반응에 비하여 상당히 좋은 제거효율을 보였다. 혼합 Fenton 공정의 최대제거효율은 magnetite-NTA 시스템으로써 약 76%의 제거효율과 magnetite-EDTA의 경우 약 56%로서 이는 Fenton-like 반응에 비하여 약 40-60% 정도의 제거효율이 향상된 결과이다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 디스플레이 광소자분야
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• pp.155-159
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• 2003

The preparation and luminescence characterization of yttrium oxide doped with trivalent europium phosphors by sol-gel method have been investigated. Aqueous metal nitrate solution was mixed with EDTA which was chosen by the most suitable material of sol-gel formation one of appled various chelating agents. we noticed that the samples when are heated with EDTA at a temperature of $100^{\circ}C$ for 1hrs, produced brownish and crisp powders due to condensation reaction on decomposition, dehydration and formation of sol-gel. Hence, when the powder pre-heated was then heated at $1200^{\circ}C$ for 3hrs in atmosphere, the luminescence characterization of resultant $Y_{2}O_{3}:Eu^{3+}$ phosphor was enhanced upto maximum 30% significantly than conventional method through increasing porous region and decreasing particle sizes.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 디스플레이 광소자분야
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• pp.151-154
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• 2003

The synthesis and luminescent properties of trivalent europium activated gadolinium oxide red phosphors by sol-gel process have been investigated. Aqueous metal nitrate solution was mixed with EDTA which was chosen by the most suitable material of sol-gel formation as chelating agents. We noticed that the samples when are heated with EDTA at a temperature of $100^{\circ}C$ for lhrs, produced brownish and crisp powders due to condensation reaction on decomposition, dehydration and formation of sol-gel. Hence, when the powder pre-heated at about $100^{\circ}C$ was then heated at $1200^{\circ}C$ for 3hrs in atmosphere, the luminescence properties of resultant $Gd_{2}O_{3}:Eu^{3+}$ phosphor was measured by SEM, FT-IT and brightness intensity was shown 20% higher than those prepared by conventional method and by other chelating agent.

• Journal of Pharmaceutical Investigation
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• 제24권3호
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• pp.109-113
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• 1994

Effects of various formulation factors using $L_8$ orthogonal arrays with the stability of doxorubicin hydrochloride injections(DHls) were investigated. The degradation of DHI may be occured by pH, temperature, light and metal ions. It is known that DHI should be stored on refrigerated condition of $4{\sim}8^{\circ}C$ because of its unstability on the room temperature. The employed factors were sodium chloride as isotonic solution, sodium bisulfite or sodium pyrosulfite as an antioxidant, disodium edetate as a chelating agent, methyl parahydroxybenzoate as a dissolution time shortening agent, and hydrochloric acid or citric acid as a pH adjusting agent at $22^{\circ}C$. From the results of $L_8$ orthogonal arrays, an optimal formula, including sodium chloride, disodium edetate, sodium bisulfite and hydrochloric acid, was obtained and the shelf-life of the formula was determined as 560 days approximately.