• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.182-185
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• 2005

울산광산 내 지표수와 토양 중의 공극수에 함유되어 있는 비소의 오염현황을 파악하고, pH와 산화-환원 전위 값의 변화에 따른 자연저감 능력을 평가하였다. 유비철석을 비롯한 비소함유 광물은 높은 산화-환원 전위 값과 낮은 pH 조건에서 해리되며, 이후 지하수의 진화과정에서 pH가 상승함에 따라 주로 5가의 비소형태로 존재하게 된다. 울산광산지역 지하수의 비소농도는 Eh가 높은 비포화대와 포화대 지하수의 경계부에서 높은 경향을 나타내며, 포화대의 상부에서는 Eh가 비교적 일정하나 비소 농도는 다양한 분포양상을 보인다. 포화대 하부에서 비소의 함량은 매우 낮으며, Eh 감소에 따라 비소 함량이 비례적으로 감소한다. 반응경로 과정에서 비소농도는 Eh<-0.1(V)인 지하수 포화대에서 가장 낮으며, pH가 상대적으로 낮고 산화-환원 전위값이 높은 비포화대에서 증가되는 경향을 보인다. 풍화 반응 정도가 높은 광미와 토양에서 비소농도 높으나, 용출실험에서 비소가 기준치 이하로 용출되는 것은 풍화반응과 토양에 의한 비소의 자연저감이 진행되고 있음을 반영한다. RMB를 이용한 중금속 제거능력 평가 실내실험에서, 산성과 알칼리 조건 모두에서 제거율이 높은 것으로 나타났다. 인회석과 철산화물질로 구성된 RMB는 친환경적이고 2차 오염문제를 극복할 수 있는 물질로서, 비소의 자연저감 능력을 향상시킬 수 있는 정화처리제로 활용이 가능할 것으로 판단된다.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.163-168
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• 2009

Negative differential resistance(NDR) behaviors of Keggin-type and Wells-Dawson-type heteropolyacids with cation, heteroatom, and polyatom substitutions were investigated by scanning tunneling microscopy. A reliable correlation between NDR peak voltage and reduction potential of heteropolyacid catalysts was established. It was found that more reducible heteropolyacid catalyst showed NDR behavior at less negative voltage, regardless of the structural difference. Thus, NDR peak voltage of heteropolyacid catalyst could be utilized as a single correlating parameter for the reduction potential of heteropolyacid catalyst.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.123-129
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• 2005

In situ permeable reactive barrier (PRB) technologies have been proposed to reductively remove organic contaminants from the subsurface environment. The major reactive material, zero valent iron ($Fe^0$), is oxidized to ferrous iron or ferric iron in the barriers, resulting in the decreased reactivity. Iron-reducing bacteria can reduce ferric iron to ferrous iron and iron reduced by these bacteria can be applied to dechlorinate chlorinated organic contaminants. Iron reduction by iron reducing bacteria, Shewanella algae BrY, was observed both in aqueous and solid phase and the enhancement of TCE removal by reduced iron was examined in this study. S. algae BrY preferentially reduced Fe(III) in ferric citrate medium and secondly used Fe(III) on the surface of iron oxides as an electron acceptor. Reduced iron formed reactive materials such as green rust ferrihydrite, and biochemical precipitation. These reactive materials formed by the bacteria can enhance TCE removal rate and removal capacity of the reactive barrier in the field.

• Economic and Environmental Geology
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• v.47 no.1
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• pp.61-69
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• 2014

As we are trying to in-situ treat (purify or immobilize) heavy metals or radionuclides in groundwater, one of the geochemical factors to be necessarily considered is the value of oxidation/reduction potential (ORP) of the groundwater. A biogeochemical impact on the characteristic ORP change of groundwater taken from the KAERI underground was observed as a function of time by adding electron-donor (lactate), electron-acceptor (sulfate), and indigenous bacteria in a laboratory condition. There was a slight increase of Eh (slow oxidation) of the pure groundwater with time under a $N_2$-filled glove-box. However, most of groundwaters that contained lactate, sulfate or bacteria showed Eh decrease (reduction) characteristics. In particular, when 'Baculatum', a local indigenous sulfate-reducing bacterium, was injected into the KAERI groundwater, it turned to become a highly-reduced one having a decreased Eh to around -500 mV. Although the sulfate-reducing bacterium thus has much greater ability to reduce groundwater than other metal-reducing bacteria, it surely necessitated some dissolved ferrous-sulfate and finally generated sulfide minerals (e.g., mackinawite), which made a prediction for subsequent reactions difficult. As a result, the ORP of groundwater was largely affected even by a slight injection of nutrient without bacteria, indicating that oxidation state, solubility and sorption characteristics of dissolved contaminants, which are affected by the ORP, could be changed and controlled through in-situ biostimulation method.

• Journal of the Korean Chemical Society
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• v.63 no.6
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• pp.486-504
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• 2019

This study analyzed achievement standards in the 2015 Science Education Standards as well as activities and assessment items in the Integrated Science, Chemistry I, and Chemistry II textbooks using science core competencies and subcomponents. All five scientific core competencies, in order of scientific thinking capacity, scientific inquiry capacity, scientific communication capacity, scientific problem solving capacity, and scientific participation and lifelong learning capacity, were included in the achievement standards of Integrated Science. Scientific thinking capacity, scientific inquiry capacity, and scientific communication capacity were included in the achievement standards of Chemistry I. The achievement standards of Chemistry II only included scientific thinking capacity. All five scientific core competencies were involved in activities of Integrated Science, Chemistry I, and Chemistry II textbooks and the highest propotion was scientific thinking capacity and scientific inquiry capacity. All five scientific core competencies were involved in assessment items of Integrated Science, Chemistry I, and Chemistry II textbooks and the highest proportion was scientific thinking capacity.

• Journal of the Mineralogical Society of Korea
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• v.24 no.4
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• pp.279-287
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• 2011

In order to identify if bacteria surviving in soils and groundwater can change the oxidation/reduction potential of groundwater, Eh values of solution that contained bacteria were measured for 2 weeks. The Eh values of the solution reacted with sulfate-reducing bacteria decreased from -120 mV to -500 mV in 5 days, and $Desulfuricans$ was superior to $Vulgaris$ in reducing the solution. The Eh value was relatively higher for the solution containing $Shewanella$, iron-reducing bacteria, showing -400 mV. During the Eh decrease by the metal-reducing bacteria, a sulfide mineral such as mackinawite (FeS) started precipitating through the microbial reducing process for sulfate and ferric iron. These results show that the ORP of natrual groundwater may be sensitive to the geomicrobial respiration. In addition, a subsurface environment where groundwater is highly reduced and sulfide minerals are largely biogenerated may be a good place to retard the migration of oxidized radionu-clides by making them precipitated as reduced forms.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.757-760
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• 2009

최근 들어 WGS 반응은 Pt과 같은 귀금속 촉매를 다양한 담체에 담지하여 낮은 온도에서 높은 활성을 지닌 촉매를 제조하기 위한 연구가 활발히 진행되고 있다. WGS 반응에서 귀금속 촉매가 높은 활성을 가지기 위해서 높은 산소저장능력(Oxygen Storage Capacity)과 산화환원능력(Redox)을 지닌 담체 개발이 필요하다. Ce-$ZrO_2$ 담체는 구조적으로 안정하며 높은 산소저장능을 가지고 있는 것으로 알려져 있다. Ce-$ZrO_2$ 구조는 Ce/Zr 비에 따라 다양한 변화가 생긴다. Ce/Zr 비가 6/4, 8/2인 경우 입방구조(Cubic)를 가지며 2/8인 경우 정방입계(Tetragonal)구조를 가진다. 이것은 담체 특성의 변화를 의미한다. 따라서, WGS 반응용 최적 담체를 선정하기 위해 Ce/Zr 비를 제조변수로 하여 담체특성을 분석하였다. 제조된 모든 담체는 공침법(Co-precipitation)을 사용하여 제조하였으며 $500^{\circ}C$에서 6시간 소성하였다. 담체 특성분석은 BET, XRD를 이용하였다. 추가적으로 제조변수를 다양화하여 담체 제조를 마쳤으며 특성분석이 진행 중이다. 분석 결과 $Ce_{0.2}Zr_{0.8}O_2$ 담체가 가장 넓은 표면적을 가지고 있으며 Ce/Zr 비가 높아질수록 표면적이 감소하는 경향을 나타내었다. Ce-$ZrO_2$ 담체의 나노결정크기는 Ce/Zr 비가 작아질수록 결정크기가 감소하는 경향을 나타내었으며 $Ce_{0.2}Zr_{0.8}O_2$가 Ce-$ZrO_2$ 담체 중에서 가장 작은 결정크기를 나타내어 3nm 이하의 나노-담체가 제조되었음을 확인하였다.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.9
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• pp.521-527
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• 2016

Nanoscale zero valent iron (nZVI) has been intensively studied for the treatment of a plethora of pollutants through reductive reaction, however, the nano size should be of concern when nZVI is considered for water treatment, due to difficulties in recovery. The loss of nZVI causes not only economical loss, but also potential risk to human health and environment. Thus, the immobilization onto coarse or structured support is essential. In this study, two representative processes for nZVI immobilization on granular activated carbon (GAC) were evaluated, and optimized conditions for synthesizing Fe/GAC composite were suggested. Both total iron content and $Fe_0$ content can be significantly affected by preparation processes, therefore, it was important to avoid oxidation during preparation to achieve higher reduction capacity. Synthesis conditions such as reduction time and existence of intermediate drying step were investigated to improve $Fe_0$ content of Fe/GAC composites. The optimal condition was two hours of $NaBH_4$ reduction without intermediate drying process. The prepared Fe/GAC composite showed synergistic effect of the adsorption capability of the GAC and the degradation capability of the nZVI, which make this composite a very effective material for environmental remediation.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.479-486
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• 2009

In natural environments, manganese (Mn) exists in the valence of +2, +3, and +4 and plays a pivotal role as a strong oxidant or reductant in the geochemical cycles of elements. Especially, Mn forms varying (oxyhydr)oxides. The oxidation state of structural Mn is characteristic to each oxide and is one of the most important factors controlling its geochemical behaviors such as solubility, sorption capacity, and redox potential. Therefore, it is important to elucidate processes governing Mn oxidation state in predicting the fate and transport of many redox sensitive elements in the environment. X-ray photoelectron spectroscopy (XPS) is a very useful method to determine the oxidation state of various elements in solid phases. In this study, the oxidation states of structural Mn in MnO, $Mn_2O_3$, $MnO_2$ were assessed based on the binding energy spectra of $Mn2p_{3/2}$ and Mn3s using XPS and were compared with those reported elsewhere. $Mn2p_{3/2}$ binding energies were determined as 640.9, 641.5, 641.8 eV for MnO, $Mn_2O_3$, $MnO_2$, respectively, which indicates that the binding energy increased with increasing Mn oxidation state. It was also noted that Ar etching may cause changes in electronic structure configuration on surface of the original sample.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.193-199
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• 2006

The catalytic oxidation of toluene over $-Al_2O_3$ supported copper-manganese oxide catalysts in the temperature range of $160-280^{\circ}C$ was investigated by employing a fixed bed flow reactor. The catalysts were characterized by BET, scanning electron microscopy (SEM), temperature-programmed reduction(TPR), temperature-programmed oxidation(TPO), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction(XRD) techniques. Catalytic oxidation of toluene was achieved at the below $280^{\circ}C$, and the optimal content of copper and manganese in the catalyst was found to be 15.0 wt％Cu-10.0 wt％Mn. From the TPR/TPO and XPS results, the redox peak of 15 Cu-10 Mn catalyst shifted to the lower temperature, and the binding energy was shifted to the higher binding energy. Furthermore, It is considered that $Cu_{1.5}Mn_{1.5}O_4$ is superior to Mn oxides and CuO in the role as active factor of catalysts from the XRD results and also catalytic activities are dependent on the redox ability and high oxidation state of catalysts.