• Title/Summary/Keyword: 환원반응

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Recovery of Metal from Tin contained Scrap by Carbothermic Reduction (탄소환원반응을 이용한 주석함유 폐자원으로부터 금속의 회수)

  • Kim, Yong-Hwan;Han, Cheol-Ung;Choe, Han-Sin;Kim, Yeong-Min;Son, Seong-Ho;Lee, Gi-Ung
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2014.11a
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    • pp.91-91
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    • 2014
  • 주석함유 2차 공정 부산물인 양극 슬라임내의 금속을 회수하기 위하여 탄소환원반응을 통해 금속 회수에 미치는 공정변수의 영향을 조사하였다. 열역학 모델링과 금속환원 실험결과, 환원 온도와 고체 환원제인 코크스(cokes)에 공정 변수에 따라 금속으로 환원이 될 수 있음을 확인하였다.

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Reactions of As(V) with Fe(II) under the Anoxic Conditions (무산소 조건에서의 Fe(II)와 As(V)의 반응에 관한 연구)

  • Jung, Woo-Sik;Lee, Sang-Hun;Chung, Hyung-Keun;Kim, Sun-Joon;Choi, Jae-Young;Jeon, Byong-Hun
    • Economic and Environmental Geology
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    • v.42 no.5
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    • pp.487-494
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    • 2009
  • The purpose of this study was to investigate the feasibility of As(V) reduction by aqueous Fe(II), and subsequent As(III) immobilization by the precipitation of As(III) incorporated magnetite-like material [i.e., co-precipitation of As(III) with Fe(II) and Fe(III)]. Experimental results showed that homogeneous As(V) reduction did not occur by dissolved Fe(II) at various pH values although the thermodynamic calculation was in favor of the redox reaction between As(V) and Fe(II) under the given chemical conditions. Similarly, no heterogeneous reduction of sorbed As(V) by sorbed Fe(II) was observed using synthetic iron (oxy)hydroxide (Goethite, ${\alpha}$-FeOOH) at pH 7. Experimental results for the effect of As(V) on the oxidation of Fe(II) by dissolved oxygen showed that As(V) inhibited the oxidation of Fe(II). These results indicate that As(V) could be stable in the presence of Fe(II) under the anoxic or subsurface environments.

Modification of Indophenol Reaction for Quantification of Reduction Activity of Nanoscale Zero Valent Iron (나노 영가철 환원 반응성의 정량 분석을 위한 수정된 인도페놀법 적용)

  • Hwang, Yuhoon;Lee, Wontae;Andersen, Henrik R.
    • Journal of Korean Society of Environmental Engineers
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    • v.38 no.12
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    • pp.667-675
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    • 2016
  • Nanoscale zero-valent iron (nZVI) has been effectively applied for environmental remediation due to its ability to reduce various toxic compounds. However, quantification of nZVI reactivity has not yet been standardized. Here, we adapted colorimetric assays for determining reductive activity of nZVIs. A modified indophenol method was suggested to determine reducing activity of nZVI. The method was originally developed to determine aqueous ammonia concentration, but it was further modified to quantify phenol and aniline. The assay focused on analysis of reduction products rather than its mother compounds, which gave more accurate quantification of reductive activity. The suggested color assay showed superior selectivity toward reduction products, phenol or aniline, in the presence of mother compounds, 4-chlorophenol or nitrobenzene. Reaction conditions, such as reagent concentration and reaction time, were optimized to maximize sensitivity. Additionally, pretreatment step using $Na_2CO_3$ was suggested to eliminate the interference of residual iron ions. Monometallic nZVI and bimetallic Ni/Fe were investigated with the reaction. The substrates showed graduated reactivity, and thus, reduction potency and kinetics of different materials and reaction mechanism was distinguished. The colorimetric assay based on modified indophenol reaction can be promises to be a useful and simple tool in various nZVI related research topics.

Reduction of High Explosives (HMX, RDX, and TNT) Using Micro- and Nano- Size Zero Valent Iron: Comparison of Kinetic Constants and Intermediates Behavior (마이크로와 나노 철을 이용한 고성능 화약물질(HMX, RDX 및 TNT)의 환원처리: 중간산물의 거동과 도역학 상수의 비교)

  • Bae, Bum-Han
    • Journal of Soil and Groundwater Environment
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    • v.11 no.6
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    • pp.83-91
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    • 2006
  • Reduction kinetics and the behaviour of intermediate of three high explosives (HMX, RDX, and TNT) were studies in batch reactors using nano- or micro- size zero valent iron(nZVI or mZVI) as reducing agent. The kinetic constants normalized by the mass of iron ($k_M$) or by the surface area ($k_{SA}$) were measured and compared along with the changes in the concentrations of intermediates. Results showed that $k_M$ and $k_{SA}$ values were not suitable to fully explain the behaviour of mother compounds and reduced intermediates in the batch reactor. The concentrations of initial explosives degradation products, such as nitroso-RDXs, nitroso-HMXs, and hydroxylamino-TNTs, were higher in mZVI treated reactor than in nZVI treated reactor, whereas more reduced polar intermediates such as TAT were accumulated in the nZVI reactor. Therefore, a new parameter, which accounted for the intermediates reduction, needs to be developed.

Deposition Mechanism of Tungsten thin Film in LPCVD System (저압 화학 기상 증착에서의 텅스텐 박막 증착 메카니즘)

  • 김성훈;송세안
    • Journal of the Korean Vacuum Society
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    • v.2 no.3
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    • pp.360-367
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    • 1993
  • 텅스텐 박막 증착의 메카니즘을 밝히기 위하여 먼저 SiH4와 WF6의 열분해 반응에 관한 열역학적 결과들과 표면 촉매 반응에 대한 이론적인 결과들을 고찰하였다. 실험적으론 저압 화학기상 증착법을 이용하여 WF6를 SiH4로 환원시켜 텅스텐 박막을 Si(100) 기판위에 증착하였으며 증착반응 중의 기판 표면의 변화를 in-situ로 측정하였다. 증착 메카니즘을 밝히기 위하여 반응기체를 WF6, SiH4, WF6+SiH4, WF6$\longrightarrow$SiH4$\longrightarrow$WF6+SiH4로 달리하여 반응시켰으며 그 때의 박막 특성과 표면 및 단면 형상을 측정하였다. 이론적인 고찰과 실험적인 결과들로부터 텅스텐 박막은 먼저 Si 기판에 의한 WF6의 환원반응으로 인한 증착과 이어서 SiH4에 의한 WF6의 환원으로 증착됨을 밝혔다.

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Reduction Characteristics of Hexavalent Chromium in Cement/Fe(II) Systems

  • 강희석;서진권;황인성;박주양
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2002.04a
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    • pp.233-236
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    • 2002
  • 다양한 산업활동에 의하여 발생하는 6가 크롬 (Cr(Ⅵ))은 대표적인 토양 및 지하수 오염물질이다. Cr(Ⅵ)은 3가크롬(Cr(III))로의 환원에 의한 침전반응으로 이동성이 저하된다고 알려져 있다. 본 연구에서는 기존의 고형화/안정화 공정에 환원.분해 반응을 추가한 2가철 기반 분해성 고형화/안정화(Degradative Solidification/Stabilization)공정에 의한 Cr(Ⅵ) 처리 특성을 고찰하였다. 회분식 실험결과 cemen/Fe(II) system내에 Cr(Ⅵ)은 환원반응 뿐만 아니라 cement에 의한 침전에 의해서도 제거됨이 밝혀졌다. Cr(Ⅵ)의 제거속도는 Fe(II)의 반응당량에 비례하는 것으로 보여진 반면, cement/solution ratio에 따른 Cr(Ⅵ) 제거동역학의 차이는 그다지 크지 않았다

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Oxygen Reduction Reaction Evaluation of Synthesized 20% Pt/C with Beat Treatment by Chemical Reduction Method (화학환원법(化學還元法)을 이용(利用)해 제조(製造)한 20% Pt/C 캐소드 촉매(觸媒)의 열처리(熱處理)에 따른 산소환원반응(酸素還元反應) 평가(評價))

  • Kim, Jin-Hwan;Kang, Suk-Min;Thube, Dilip.R.;Ryu, Ho-Jin
    • Resources Recycling
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    • v.18 no.5
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    • pp.12-18
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    • 2009
  • The 20% Pt/C catalysts were synthesized using the chemical reduction method for polymer electrolyte fuel cell cathode and were heat-treated in the temperature range from 300 to $600^{\circ}C$. The oxygen reduction reaction of the catalysts was evaluated using the electrochemical measurement. The oxygen reduction reaction of the heat-treated Pt/C at $300^{\circ}C$ had high catalytic activity and the oxygen reduction reaction current of that was 2 times than that of non-heat treatment catalyst. It is considered that the change of the crystallinity and particle size by heat treatment could increase the catalytic activity.

Kinetics of 2, 4, 6-Trinitrotoluene reduction by zero valent iron (금속 철을 이용한 TNT 환원시의 동역학 산정)

  • 배범한
    • Journal of Korea Soil Environment Society
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    • v.4 no.1
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    • pp.97-108
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    • 1999
  • Reduction 2, 4, 6-trinitrotoluene by zero valent iron was studied in a batch reactor under anoxic conditions. Results showed that the removal of trinitrotoluene (TNT)followed a pseudo-first order reaction and the rate was linearly dependent on the available reactive surfau area of the zero valent iron surface area, resulting a rate constant of 0.0981min$^{1}m$$^{-2}m$. High concentrations of the final product, presumably triaminotoluene which needs to be treated by other means, accumulated in the solution. However , little amount of TAT was extracted from the metal surface by using acetonitrile or phosphate buffered water (pH 7.0). Other common major intermediate in biological TNT degradation, a group of aminodinitrotoluenes, was not detected in the solution. Therefore, it is postulated that the reduction of nitro group by $Fe^0$ occurs simultaneously in all three positions and a TNT reduction model by zero valent iron was suggested.

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Studies on the Antibacterial Effects of Electrolyzed Reduced Water (환원전리수의 항균력 연구)

  • Park, Hye-Lin;Kim, Yoon-Kyoung;Ryoo, Kun-Kul;Lee, Yoon-Bae;Lee, Jong-Kwon;Lee, Mi-Young
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.6 no.2
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    • pp.215-221
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    • 2005
  • The antibacterial effects of electrolyzed reduced water on the bacterial growth were studied in this investigation. Upon treating with electrolyzed reduced water for 2 minutes, about 70% Escherichia coli and 61% Bacillus cereus were controlled. When these two bacteria were exposed to electrolyzed reduced water for 30 minutes, about 89% Escherichia coli and 94% Bacillus cereus were controlled. About 55% Pseudomonas aeruginosa was also controlled upon treateing with electrolyzed reduced water for 2 minutes, and 65% Pseudomonas aeruginosa was controlled during 4 hour incubation. When Staphylococcus epidermidis was treated with electrolyzed reduced water for 4 hours, 73% of the bacterial growth was inhibited, while only 44% Staphylococcus aureus.subsp.aureus was controlled with electrolyzed reduced water for 4 hours.

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