• Polymer(Korea)
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• v.25 no.6
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• pp.826-832
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• 2001

In this study, PPy/gold/mylar type electroactive bi-layer actuator was prepared by the electrochemical polymerization of pyrrole onto the gold/mylar film and the actuation characteristics were studied using bending beam method. Conducting polymer-based actuators undergo volumetric changes due to the movement of dopant ions into the film during the electrical oxidation process. The bilayer films exhibited different actuation characteristics depending on dopant ion size. It was observed that the relatively small dopant ion (i.e. toluene sulfonate) moved into the PPy film at oxidized state, so volume expanded to result in bending motion. In case of the film having large dopant ion (i.e. dodecylbenzenesulfonate), volume expansion was observed at reduced state. This is due to the incorporation of $Na^+$ counterion with water molecules, while the large dopant ion was fixed in the film due to the limited mobility during tile redox process.

• 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.

• Resources Recycling
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• v.29 no.5
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• pp.64-72
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• 2020

When the multi-stage combustion process is applied to the cement kiln to reduce nitrogen oxide emissions in the cement industry, oxidation/reduction section that can increase combustion efficiency by reducing NO_x to NO and completely burning unburned materials is essential In this study, when applied the oxidation/reduction system of the cement kiln preheater and calciner, the optimal oxidation/reduction calcination crisis that can secure the quality stability of the final product, cement clinker, was to be observed macroscopically, and the mass change of raw materials according to the burning conditions, decarbonation rate, and calcination rate were investigated. The results showed that the thermal decomposition of raw materials tends to be promoted in the oxidation condition rather than in the reduction condition, and that the thermal decomposition of limestone, which has a relatively high CaO content, is carried out later than that of cement raw meal, which is thought to be caused by the CO₂ fractionation in the kiln. The thermal decomposition properties of raw materials according to oxidation/reducing burning condition showed a relatively large difference in temperature range lower than normal limestone themal decomposition temperature, which is thought to be expected to improve the thermal efficiency of raw materials according to the formation of oxidation condition in the section 750℃ of burning temperature. However, for this study, lab scale. Because there is a difference from the field process as a scale study, it is deemed necessary to verify the actual test results of the pilot scale.

• Journal of the Mineralogical Society of Korea
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• v.25 no.3
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• pp.155-162
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• 2012

We observed characteristic oxidation and dissolution phenomena induced by dissolved oxygen for mackinawite that is produced via sulfate-reducing bacteria (SRB) living in anaerobic environments such as soils and groundwater. We tried to recognize the role of the sulfide minerals that usually coexist with some stabilized radionuclides (e.g., reduced uranium), which can be reoxidized and redissolved by an oxygen-rich groundwater invaded into a contaminated area. The mackinawite produced by 'Desulfovibrio desulfuricans', a sulfate-reducing bacterium, was conducted to be dissolved for 2 weeks by some oxidants such as 'hydrogen peroxide' and 'sodium nitrite'. Although mineralogical oxidation and dissolution characteristics were different from each other according to the oxidants, the initially oxidized solution was early stabilized through the oxygen consumption by ${\mu}m$-sized sulfide particles and the resultant increase of sulfate in solution. From these results, we can anticipate that the large amount of sulfide minerals generated by SRB can not only repress the anoxic environment to be disturbed by the consumption of oxygen in groundwater, but also contribute to stabilize the reduced/precipitated radionuclides as a buffer material for a long time.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.43-47
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• 2007

Electrochemical rectification at electrode chemically modified with redox active agents isolated at monolayer level was considered. Formulation of the rising part of linear sweep voltammogram at steady and rotating disc electrode was introduced.

• Food Science and Preservation
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• v.7 no.4
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• pp.395-402
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• 2000

To enlarge application field of electrolyzed acid-water(EAW) on food industry, the changes of EAW properties by storage conditions and heating were investigatet. It was showed that storing EAW in closed container is mon effective to keep up the oxidation-reduction potentials(ORP), hyperchloride content and pH than stored in opened ones. ORP of EAW stored in closed container could be kept mon than 1 month as 1,150 mV levels. Ruing heating from 2$0^{\circ}C$ to 95$^{\circ}C$, ORP was increased to 1,150 mV levels at 95$^{\circ}C$ after gradual decrease to 5$0^{\circ}C$. Tyrosinase activity was decreased approximately to 26%~35% in EAW having a 950 mV~1,140 mV ORP. Also it was confirmed that EAW has anti-browning effect as sliced apple and potato, and their juices treated with EAW had conspicous difference in their $\Delta$E value. 12 kinds of pesticides such as aldrine, capful diazinon, diedrin, $\alpha$-endosulfan $\beta$-endosulfan, endosulfan sulfate, endrin, $\alpha$-BHC, o,p'-DDT, procymidone, PCNB added in EAW were recovered from ND~73.6% comparing to ones added in distilled water. The recovered amounts of pesticides, procymidone and diazinon in lettuce after soaking in EAW were 1.12 ppm and ND, compared with those of amounts soaked in distilled water were 3.67 ppm and 3.05 ppm respectively. So, it seems that EAW has potentials to promote the degradation of pesticides.

• Journal of Wetlands Research
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• v.6 no.2
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• pp.65-71
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• 2004

The most significant effect of excess water in wetlands is the isolation of the soil from the atmosphere and the prevention of O2 from diffusing into soil. The blockage of atmospheric O2 induces biological and chemical processes that change soil from oxidized into reduced state. When dry soil develop into hydric soil, redox potential is dropping. The redox potential is a indicator of hydric soil and affect chemical function of wetlands. To reveal characteristics of wetland soil, redox potential was measured in Jinkwannaedong ecological conservation area from May in 2003 to March in 2004. Redox potentials in May ranged from 5 mV at 25 cm depth to 200 mV at 10 cm depth. It decreased to about -200 m V at all depths and continued until October. In winter, redox potential was slowly increased; it was the highest at 5 cm depth and lowest at 20 cm depth. Annual variations of redox potential in 20 cm depth showed the same pattern at 5 sites; low in growing season and high in non-growing season. This results indicates that soils of study sites are in hydric state and methanogenesis is occurring in Jinkwannaedong ecological conservation area.

• Microbiology and Biotechnology Letters
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• v.49 no.2
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• pp.225-238
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• 2021

CH₄-oxidizing and N₂O-reducing bacterial consortia were enriched from the rhizosphere soils of maize (Zea mays) and tall fescue (Festuca arundinacea). Illumina MiSeq sequencing analysis was performed to comparatively analyze the bacterial communities of the consortia with those of the rhizosphere soils. Additionally, the effect of root exudate on CH₄ oxidation and N₂O reduction activities of the microbes was evaluated. Although the inoculum sources varied, the CH₄-oxidizing and N₂O-reducing consortia derived from maize and tall fescue were similar. The predominant methanotrophs in the CH₄-oxidizing consortia were Methylosarcina, Methylococcus, and Methylocystis. Among the N₂O-reducing consortia, the representative N₂O-reducing bacteria were Cloacibacterium, Azonexus, and Klebsiella. The N₂O reduction rate of the N₂O-reducing consortium from maize rhizosphere and tall fescue rhizosphere increased by 1.6 and 2.7 times with the addition of maize and tall fescue root exudates, respectively. The CH₄ oxidization activity of the CH₄-oxidizing consortia did not increase with the addition of root exudates. The CH₄-oxidizing and N₂O-reducing consortia can be used as promising bioresources to mitigate non-CO₂ greenhouse gas emissions during remediation of oil-contaminated soils.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.2
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• pp.89-97
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• 2010

$Al_2O_3$, $TiO_2$, $ZrO_2$, $Al_2O_3-TiO_2$, $Al_2O_3-ZrO_2$, 및 $TiO_2-ZrO_2$ 혼합 산화물을 지지체로 한 Ni 기반 혼합 산화물을 졸-겔법으로 제조하였다. 제조된 혼합 산화물은 1173K에서 열처리 한 후 구조적 특성 변화를 전자현미경 및 X-선 회절 분석을 이용하여 관찰하였으며, 수소를 이용한 승온 환원(TPR; temperature-programmed reduction) 실험을 통하여 1173K 까지 각 시료들의 환원 피크를 비교 고찰하였다. $Al_2O_3$ 또는 $TiO_2$ 가 혼합된 시료의 경우 1173K 에서의 열처리 후 니켈 알루미네이트 또는 니켈 티타네이트와 같은 새로운 결정상의 생성이 관찰되었으나 $ZrO_2$가 혼합된 경우에는 새로운 결정상의 생성이 관찰되지 않았다. TPR 결과에 의하면, $Al_2O_3$ 또는 $TiO_2$를 혼합된 시료의 경우 벌크 NiO의 TPR 결과와는 달리 생성된 새로운 결정상에 기인한 여러 개의 환원 피크가 나타났으나 $ZrO_2$를 혼합한 경우 벌크 NiO와 비슷한 환원 피크를 보였다. TPR 결과를 기초로 Arrhenius plot 으로부터 각 혼합 산화물들의 수소 환원 활성화 에너지를 도출하였다. $ZrO_2$를 지지체로 사용하는 경우 다른 혼합 산화물들보다 지지체로서 안정한 혼합 산화물상을 형성한다는 것을 지시하듯이 상대적으로 가장 낮은 활성화 에너지를 나타냈다.

• 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.