• 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.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.379-384
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• 2017

An electrochemical reduction of a mixture of NiO and rare earth oxides has been conducted to increase the reduction degree of rare earth oxides. Cyclic voltammetry (CV) measurement was carried out to determine the electrochemical reduction behavior of the mixed oxide in molten LiCl medium. Constant voltage electrolysis was performed with various supplied charges to understand the mechanism of electrochemical reduction of the mixed oxide as a working electrode. After completion of the electrochemical reduction, crystal structure of the reaction intermediates was characterized by using an X-ray diffraction method. The results clearly demonstrate that the rare earth oxide was converted to RE-Ni intermetallics via co-reduction with NiO.

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.345-353
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• 2002

The purpose of this study was to analyze the influence of mental capacity and understanding of the oxi-dation-reduction concepts on the completion of the balancing redox equations. Participants were 92 senior high school students and 57 science high school students. Tests were conducted to measure the mental capacity, the understanding of the oxidation-reduction concepts and the completion of the balancing redox equations and the influence on the per-formance was analyzed. The performance of the senior high school students increased as the mental capacity increased, but the performance of science high school students did not change by mental capacity. Most of senior high school stu-dents couldn't understand the oxidation-reduction concepts well. Most of science high school students, however, under-stood the concepts completely and partially. The students who had a good understanding of the oxidation-reduction concepts showed a good performance for both senior and science high school students, regardless of the problem pattern.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.115.2-115.2
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• 2007

• Clean Technology
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• v.21 no.2
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• pp.96-101
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• 2015

Hematite reduction using hydrogen was conducted and the various process parameters were closely observed. A lab scale fluidized bed unit was designed especially for this study. The optimal values of the gas velocity, reduction time and temperature were evaluated. The values which indicated the highest reduction rate were set as fixed parameters for the following tests starting with the reduction time of 30 minutes and 750 ℃ of temperature. Among these variables the one with the highest interest was the gas specific consumption. It will tell the amount of the gas which is required to achieve a reduction rate of over 90% at the optimal conditions. This parameter is important for the scale up of the lab scale unit. 1,500 Nm³/ton-ore was found to be the optimal specific gas consumption rate at which the reduction rates exhibit the highest values for hematite.

• 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.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1661-1666
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• 2010

본 연구의 목적은 충북대학교 부속농장에서 2009년 영농기간을 중심으로 담수된 논에서의 산화환원전위(Eh)의 변화와 시비에 따라 영양물질인 인(P)의 농도변화 특성을 파악함으로써, 논으로 부터의 인의 유출제어에 관한 기초 자료를 제공하는데 있다. 이 연구는 2009년 5월부터 11월까지 논에서 담수의 총인(T-P)과 인산염 인($PO_4$-P)의 농도변화와 토양의 산화환원전위(Eh)와의 관계 특성을 파악하였다. 관개기의 논에서 인은 분얼비 시기에 인성분이 시비되지 않았는데도 불구하고 T-P농도가 0.68 mg/L로 높게 나타났다. 이는 담수의 영향으로 논이 환원상태로 되어, 논바닥에 침전된 철이온에 흡착되어 있던 인이 철이온의 환원으로 함께 용출하기 때문이라고 생각된다. 높은 Eh는 산화경향을, 낮은 Eh는 환원경향을 나타낸다. 본 연구기간 동안의 Eh 값은 연속적으로 담수되었던 7월 중순까지는 74~112 mV 가량 나타냈고, 그 이후에는 담수상태가 아닌 경우가 많아 179~636 mV로 높게 나타났다. 논 담수의 T-P와 $PO_4$-P 농도는 분얼비 직후 1주일후까지 같이 상승하다가 T-P농도는 약 2주일까지 더 상승한 반면 $PO_4$-P 농도는 하강하였는데 이는 논 토양이 환원상태로 되면서 바닥에 있던 입자성 인이 논 표면으로 떠올랐기 때문으로 사료된다. 그 후에는 담수가 끝나는 시점까지인 농도는 낮아졌다. 관개초기에 인의 농도는 비교적 높게 나타났지만, 7월 이후로는 작물의 생장에 필요한 영양물질 섭취 등으로 인 농도가 낮게 나타났는데 이는 7월 이후의 논은 인의 유출을 억제하고 있는 것으로 추정된다. 또한 논 담수위의 증감에 따른 $PO_4$-P 농도와 Eh 값을 회귀분석 한 결과 각각 정의 상관관계와 부의 상관관계가 있는 것으로 나타났다. 이와 같이 논 담수 및 시비에 따른 인의 유출부하 특성과 산화환원전위(Eh)의 변화 특성이 규명된다면, 향후 환경부하가 작은 물관리가 가능해 질 것으로 판단된다.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.3 s.32
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• pp.55-62
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• 2004

The oxidation of pure Sn and high Pb-Sn alloys was investigated under different oxidizing conditions of temperature and humidity. Both the chemical nature and the amount of oxides were characterized using electrochemical reduction analysis by measuring the electrolytic reduction potential and total transferred electrical charges. For pure tin, SnO grew faster under humid condition than in dry air at $85^{\circ}C$. A very thin (<10 ${\AA}$) layer of SnO, was formed on the top surface under humid condition. The mixture of SnO and $SnO_2$ was found for oxidation at $150^{\circ}C$. XPS and AES were performed to support the result of oxide reduction.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.19-32
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• 2010

Electrolytic reduction technology is essential for the purpose of adopting pyroprocessing into spent oxide fuel as an alternative option in a back-end fuel cycle. Spent fuel consists of various metal oxides, and each metal oxide releases an oxygen element depending on its chemical characteristic during the electrolytic reduction process. In the present work, an electrolytic reduction behavior was estimated for voloxidized spent fuel based on the assumption that each metal-oxygen system is independent and behaves as an ideal solid solution. The electrolytic reduction was considered as a combination of a Li recovery and chemical reactions between the metal oxides such as uranium oxide and the produced Li metal. The calculated result revealed that most of the metal oxides were reduced by the process. It was evaluated that a reduced fraction of lanthanide oxides increased with a decreasing $Li_2O$ concentration. However, most of the lanthanides were expected to be stable in their oxide forms. In addition, a semi-empirical model for describing $U_3O_8$ electrolytic reduction behavior was proposed by considering Li diffusion and a chemical reaction between $U_3O_8$ and Li. Experimental data was used to determine model parameters and, then, the model was applied to calculate the reduction yield with time and to estimate the required time for a 99.9% reduction.

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.353-363
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• 2002

In this study, characteristics of the problem solving process of the balancing redox equations was ana-lyzed by mental capacity and problem solving methods, and the pertinent teaching and learning guidance for oxidation-reduction unit was suggested. Participants were 79 senior high school students and 57 science high school students. Tests were conducted to measure the mental capacity, the understanding of the oxidation-reduction concepts and the com-pletion of the balancing redox equations. The framework was made to find the patterns of failure and success. As the analysis of the influence on the performance of mental capacity,understanding of the oxidation-reduction concepts, and problem solving methods, students who had lower understanding of oxidation-reduction concepts selected the trial and error method, and their performance were influenced by mental capacity. The students that had higher understanding of the oxidation-reduction concepts had good performance by using oxidation number method regardless of their mental capacity. As the results of analysis for the patterns, the success patterns of solving the problems, those of mostly the sci-ence high school students, were the cases of using oxidation number method well and lessening problem solving steps. The patterns of failure in solving problems by using trial and error method showed that students had mistakes in cal-culating, errors in making unknown equations, no consideration for all variables, or stopped solving the complicated problems. The patterns of failure in solving problems by using oxidation number method showed that many students had wrong oxidation number or no consideration for mass and charge balance.