• Environmental Engineering Research
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• 제16권4호
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• pp.187-203
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• 2011

Chlorophenols (CPs) are widely used industrial chemicals that have been identified as being toxic to both humans and the environment. Zero valent iron (ZVI) and iron based bimetallic systems have the potential to efficiently dechlorinate CPs. This paper reviews the research conducted in this area over the past decade, with emphasis on the processes and mechanisms for the removal of CPs, as well as the characterization and role of the iron oxides formed on the ZVI surface. The removal of dissolved CPs in iron-water systems occurs via dechlorination, sorption and co-precipitation. Although ZVI has been commonly used for the dechlorination of CPs, its long term reactivity is limited due to surface passivation over time. However, iron based bimetallic systems are an effective alternative for overcoming this limitation. Bimetallic systems prepared by physically mixing ZVI and the catalyst or through reductive deposition of a catalyst onto ZVI have been shown to display superior performance over unmodified ZVI. Nonetheless, the efficiency and rate of hydrodechlorination of CPs by bimetals depend on the type of metal combinations used, properties of the metals and characteristics of the target CP. The presence and formation of various iron oxides can affect the reactivities of ZVI and bimetals. Oxides, such as green rust and magnetite, facilitate the dechlorination of CPs by ZVI and bimetals, while oxide films, such as hematite, maghemite, lepidocrocite and goethite, passivate the iron surface and hinder the dechlorination reaction. Key environmental parameters, such as solution pH, presence of dissolved oxygen and dissolved co-contaminants, exert significant impacts on the rate and extent of CP dechlorination by ZVI and bimetals.

• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.28-32
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• 2016

There are a few thousand abandoned metal mines in South Korea. The abandoned mines cause several environmental problems including releasing acid mine drainage (AMD), which contain a very high acidity and heavy metal ions such as Fe, Cu, Cd, Pb, and As. Iron oxides can be formed from the AMD by increasing the solution pH and inducing precipitation. Current study focused on the formation of iron oxide in an AMD and used the oxide for adsorption of heavy metals. The heavy metal adsorbed iron oxide was separated with a superconducting magnet. The duration of iron oxide formation affected on the type of mineral and the degree of magnetization. The removal rate of heavy metal by the adsorption process with the formed iron oxide was highly dependent on the type of iron oxide and the solution pH. A high gradient magnetic separation (HGMS) system successfully separated the iron oxide and harmful heavy metals.

• 한국재료학회지
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• 제18권4호
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• pp.218-221
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• 2008

A $Fe(OH)_2$ suspension was prepared by mixing iron sulfate and a weak alkali ammonia solution. Following this, iron oxides were synthesized by passing pure oxygen through the suspension (oxidation). The effects of different reaction temperatures ($30^{\circ}C$, $50^{\circ}C$, $70^{\circ}C$) and equivalent ratios ($0.1{\sim}10.0$) on the formation of iron oxides were investigated. An equilibrium phase diagram was established by quantitative phase analysis of the iron oxides using the Rietveld method. The equilibrium phase diagram showed a large difference from the equilibrium phase diagram of Kiyama when the equivalent ratio was above 1, and single $Fe_3O_4$ phase only formed above an equivalent ratio 2 at all reaction temperatures. Kiyama synthesized iron oxide using iron sulfate and a strong alkali NaOH solution.

• 한국자기학회지
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• 제7권6호
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• pp.314-320
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• 1997

폴리에스터 film 위에 자성도료를 도포 후 자성체의 배향 거동을 살펴보았다. static orientation 처리하여 평가한 결과 자성도료가 도포된 film이 배향자석을 통과할 때 배향자석의 입구측과 출구측에서 배향성이 최대로 나타나나 출구측이 약간 낮게 나타났으며 배향자석의 출구를 지나면서 static energy의 감소와 entropy의 증가에 의하여 도막의 건조과정 중 배향성은 서서히 감소되다가 완전히 건조되면서 일정한 수준으로 유지되었다. 그리고 film의 중심부보다 양쪽의 edge 부위에서의 배향성은 떨어지는데 그 원인은 배향자석의 형태에 기인하는 것으로 생각된다. Dynamic orientation 처리하여 평가한 결과 자기 tape에서 자성도막의 배향성이 향상됨에 따라 전 대역에서의 출력 특성은 향상되었으며 건조 조건에 따라서도 tape의 배향성이 변하였다. 따라서 자기 tape의 출력특성을 향상시키기 위하여는 배향자석의 설계 및 자성도료의 건조 조건 등의 검토가 필요하다고 생각한다.

• 한국해양학회지:바다
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• 제14권3호
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• pp.127-133
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• 2009

동해 울릉분지에서 망간산화물과 철산화물의 유기물 분해 기여율을 정량화하기 위하여 6개의 박스형 시추퇴적물을 채집하였다. 수심이 2,000 m 이상인 울릉분지 표층퇴적물에서 유기탄소 함량은 2.6% 가량으로 육상기원 유기물 유입이 많은 흑해와 용승 해역인 칠레 주변해역들과 비슷했다. 울릉분지에 위치한 정점들에서 망간산화물 함량은 퇴적물 최상부에서 2% 이상으로 매우 높았고, 철산화물 함량은 울릉분지 표층 $1{\sim}4cm$ 내외에서 2% 가량의 최고값을 나타냈다. 그러나 대륙사면 정점들에서 망간산화물과 철산화물 함량은 분지처럼 높은 값을 보이지 않았다. 동해 울릉분지에서 2% 이상으로 높은 망간산화물 함량은 높은 유기탄소 함량과 사면보다 비교적 느린 퇴적속도 때문이거나 망간 이온이 저탁류를 통해 사면에서 분지로 이동한 것으로 예상된다. 망간산화물 환원율은 $0.3{\sim}0.57\;mmol\;m^{-2}\;day^{-1}$의 범위를 보였고, 철산화물 환원율은 $0.10{\sim}0.24\;mmol\;m^{-2}\;day^{-1}$의 범위를 나타냈다. 울릉분지에서 금속산화물은 유기물 분해에 $13{\sim}26%$ 정도를 차지하였으며, 이는 칠레 용승 해역과 유사하고, 덴마크 연안보다 낮은 값이다.

• 한국수소및신에너지학회논문집
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• 제17권1호
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• pp.21-30
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• 2006

[ $M/Fe_2O_3$ ] (M=Rh, Ce and Zr) mixed oxides were prepared using urea method to develop a medium for chemical hydrogen storage by their redox cycles. And their redox behaviors by repeated cycles were studied using temperature programmed reaction(TPR) technique. Additives such as Rh, Ce and Zr were added to iron oxides in order to lower the reaction temperature for reduction by hydrogen and re-oxidation by water-splitting. From the results, concentration of urea used as a precipitant had little effect on particle size and reduction property of iron oxide. TPR patterns of iron oxide consisted of two reduction peaks due to the course of $Fe_2O_3\;{\rightarrow}\;Fe_3O_4\;{\rightarrow}\;Fe$. The results of repeated redox tests showed that Rh added to iron oxide have an effect on lowering the re-oxidation temperature by water-splitting. Meanwhile, Ce and Zr additives played an important role in prevention of deactivation by repeated cycles. Finally, Fe-oxide(Rh, Ce, Zr) sample added with Rh, Ce and Zr showed the lowest re-oxidation temperature by water-splitting and maintained high $H_2$ recovery in spite of the repeated redox cycles. Consequently, it is expected that Fe-oxide(Rh, Ce, Zr) sample can be a feasible medium for chemical hydrogen storage using redox cycle of iron oxide.

• Korean Chemical Engineering Research
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• 제46권6호
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• pp.1029-1038
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• 2008

전이금속 산화물의 전구체가 들어있는 합성모액을 수열 반응시켜 전이금속 산화물이 고정된 하이드로탈사이트를 제조하여 이들에 대한 이산화질소의 흡착 성질을 조사하였다. 전이금속 산화물의 분산도, 이산화질소의 흡착량 및 흡착상태를 XRD, SEM, XPS, 질소 흡착등온선, 중량식 흡착법, FT-IR, 승온탈착법으로 조사하였다. 전이금속 산화물은 주로 하이드로탈사이트의 표면에 분산 담지되었으며, 철과 니켈 산화물이 고정된 하이드로탈사이트에 이산화질소가 많이 흡장되었다. 철 산화물이 표면에 분산되어 담지되면 이산화질소의 흡장량이 많지만, 철 산화물이 지나치게 많이 담지되면 덩어리져서 표면의 염기점을 차폐하므로 이산화질소의 흡장량이 오히려 줄어들었다. 철 산화물의 고정량이 적절하면 하이드로탈사이트에서 이산화질소의 흡장세기는 약해지지만, 흡장량은 많아지고 수열 안정성이 증진되었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권6호
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• pp.14-21
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• 2016

This study evaluated the applicability of stabilization of arsenic (As)-contaminated soil with iron (Fe) oxides at the former Janghang smelter site. Three Fe oxides (magnetite, goethite, and hematite) were tested as stabilizing agents to one soil sample collected from the study site. Amendment of 5% of magnetite, goethite, or hematite for one week showed the 64, 58, and 36% of reduction of the SBRC (Solubility/Bioavailability Research Consortium)-extractable (bioaccessible) As, respectively. Duration of stabilization more than one week did not show an additional reduction in SBRC-extractable As. Amendment of 5% of magnetite, which showed the highest As stabilization efficiency, was applied to 24 soil samples collected from the same site for one week, and 72% of reduction in the bioaccessible As was observed. The potential carcinogenic human health risk at the study site caused by As was $1.7{\times}10^{-5}$, which could be reduced to $8.1{\times}10^{-6}$ by the amendment of 5% magnetite for one week.

• Environmental Engineering Research
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• 제14권2호
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• pp.134-139
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• 2009

In this study, oxidation of As (III) as well as removal of total arsenic by adsorbents coated with single oxides or multi-oxides (Fe (III), Mn (IV), Al (III)) was investigated. In addition, multi-functional properties of adsorbents coated with multi-oxides were evaluated. Finally, application of activated carbon impregnated with Fe or Mn-oxides on the treatment of As (III) or As (V) was studied. As (V) adsorption results with adsorbents containing Fe and Al shows that adsorbents containing Fe show a greater removal of As (V) at pH 4 than at pH 7. In contrast adsorbents containing Al shows a favorable removal of As (V) at pH 7 than at pH 4. In case of iron sand, it has a negligible adsorption capacity for As (V) although it contains 217.9 g-Fe/kg-adsorbent, Oxidation result shows that manganese coated sand (MCS) has the greatest As (III) oxidation capacity among all metal oxides at pH 4. Oxidation efficiency of As (III) by IMCS (iron and manganese coated sand) was less than that by MCS. However the total removed amount of arsenic by IMCS was greater than that by MCS.

• 자원리싸이클링
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• 제7권4호
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• pp.76-80
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• 1998

국내 산화철에 대한 관련업계의 ICP 성분분석체계의 확립을 위해서 산화철분과위원회에서는 분석실무팀을 구성하여 1년간에 걸쳐 많은 시료에 대한 분석을 행하였다. 분기별 회합을 가져 각사의 성분분석 Data에 대하여 상호비교 및 의견교환을 하여 각사의 문제점을 개선하였다. 제1회 회합때는 각사별 성분분석 Datark 상당한 편차를 보였으나, 회가 거듭할수록 보완.개선되어 제3회 분석 Data에서는 각 사별 편차범위가 $\pm$20% 이내로 줄었고, 이러한 결과는 선진 일본철강업체에 비해서도 대등한 수준으로 평가될 수 있다.