• Advances in environmental research
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• 제2권3호
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• pp.167-177
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• 2013

We investigated that removal of aqueous U(VI) by nano-sized Zero Valent Iron (nZVI) and Fe(II) bearing minerals (controls) in this study. Iron particles showed different U(VI) removal efficiencies (Mackinawite: 99%, green rust: 95%, nZVI: 91%, magnetite: 87%, pyrite: 59%) due to their different PZC (Point of Zero Charge) values and surface areas. In addition, noticeable amount of surface Fe(II) (181 ${\mu}M$) was released from nZVI suspension in 6 h and it increased to 384 ${\mu}M$ in the presence of U(VI) due to ion-exchange of U(VI) with Fe(II) on nZVI surface. Analysis of Laser-Induced Breakdown Detection (LIBD) showed that breakdown probabilities in both filtrates by 20 and 200 nm sizes was almost 24% in nZVI suspension with U(VI), while 1% of the probabilities were observed in nZVI suspension without U(VI). It indicated that Fe(II) colloids in the range under 20 nm were generated during the interaction of U(VI) and nZVI. Our results suggest that Fe(II) colloids generated via ion-exchange process should be carefully concerned during long-term remediation site contaminated by U(VI) because U could be transported to remote area through the adsorption on Fe(II) colloids.

• 자원리싸이클링
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• 제2권2호
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• pp.16-21
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• 1993

본 연구에서는 폐수중에 함유된 철이온을 제거하기 위하여 2가와 3가 칠이온을 함유하는 용액의 pH를 침전점이상으로 조절함으로서 형성된 수산화철 침전의 침강 특성을 조가하여 다음과 같은 결과를 얻었다. 수산 이온의 농도 증가는 수산화철 침전의 침강 속도를 빠르게 하고 이때 CaO가 효과적이었다. 고분자 엉김제는 수산화철 침전의 초기 침강 속도를 빨라지게 하지만 과량은 침강 속도를 저하시킨다. 수산화철 침전의 농도가 높아지면 침강 속도가 크게 감소되므로 수산화물로서 침전시켜 제거할 철이온의 농도는 $10^{-2}$mol/ㅣ이하로 조절됨이 바람직하다.

• Journal of Microbiology and Biotechnology
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• 제29권1호
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• pp.105-113
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• 2019

Although siderophore compounds are mainly biosynthesized as a response to iron deficiency in the environment, they also bind with other metals. A few studies have been conducted on the impact of heavy metals on the siderophore-mediated iron uptake by microbiome. Here, we investigated siderophore production by a variety of rhizosphere fungi under different concentrations of $Zn^{2+}$ ion. These strains were specifically isolated from the rhizosphere of Panax ginseng (Korean ginseng). The siderophore production of isolated fungi was investigated with chrome azurol S (CAS) assay liquid media amended with different concentrations of $Zn^{2+}$ (50 to $250{\mu}g/ml$). The percentage of siderophore units was quantified using the ultra-violet (UV) irradiation method. The results indicated that high concentrations of $Zn^{2+}$ ion increase the production of siderophore in iron-limited cultures. Maximum siderophore production by the fungal strains was detected at $Zn^{2+}$ ion concentration of $150{\mu}g/ml$ except for Mortierella sp., which had the highest siderophore production at $200{\mu}g/ml$. One potent siderophore-producing strain (Penicillium sp. JJHO) was strongly influenced by the presence of $Zn^{2+}$ ions and showed high identity to P. commune (100% using 18S-rRNA sequencing). The purified siderophores of the Penicillium sp. JJHO strain were chemically identified using UV, Fourier-transform infrared spectroscopy (FTIR), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF-MS) spectra.

• Journal of Electrochemical Science and Technology
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• 제12권4호
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• pp.424-430
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• 2021

The element iron (Fe) is affordable and abundantly available, and thus, it finds use in a wide range of applications. As regards its application in rechargeable lithium-ion batteries (LIBs), the electrochemical reactions of Fe must be clearly understood during battery charging and discharging with the LIB electrolyte. In this study, we conducted systematic electrochemical analyses under various voltage conditions to determine the voltage at which Fe corrosion begins in general lithium salts and organic solvents used in LIBs. During cyclic voltammetry (CV) experiments, we observed a large corrosion current above 4.0 V (vs. Li/Li⁺). When a constant voltage of 3.7 V (vs. Li/Li⁺), was applied, the current did not increase significantly at the beginning, similar to the CV scenario; on the other hand, at a voltage of 3.8 V (vs. Li/Li⁺), the current increased rapidly. The impact of this difference was visually confirmed via scanning electron microscopy and optical microscopy. Our X-ray photoelectron spectroscopy measurements showed that at 3.7 V, a thick organic solid electrolyte interphase (SEI) was formed atop a thin fluoride SEI, which means that at ≥3.8 V, the SEI cannot prevent Fe corrosion. This result confirms that Fe corrosion begins at 3.7 V, beyond which Fe is easily corrodible.

• 상하수도학회지
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• 제24권3호
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• pp.341-349
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• 2010

It is well known that manganese is hard to oxidize under neutral pH condition in the atmosphere while iron can be easily oxidized to insoluble iron oxide. The purpose of this study is to identify removal mechanism of manganese in the D water treatment plant where is treating bank filtered water in aeration and rapid sand filtration. Average concentration of iron and manganese in bank filtered water were 5.9 mg/L and 3.6 mg/L in 2008, respectively. However, their concentration in rapid sand filtrate were only 0.11 mg/L and 0.03 mg/L, respectively. Most of the sand was coated with black colored manganese oxide except surface layer. According to EDX analysis of sand which was collected in different depth of sand filter, the content of i ron in the upper part sand was relatively higher than that in the lower part. while manganese content increased with a depth. The presence of iron and manganese oxidizing bacteria have been identified in sand of rapid sand filtration. It is supposed that these bacteria contributed some to remove iron and manganese in rapid sand filter. In conclusion, manganese has been simultaneously removed by physicochemical reaction and biological reaction. However, it is considered that the former reaction is dominant than the latter. That is, Mn(II) ion is rapidly adsorbed on ${\gamma}$-FeOOH which is intermediate iron oxidant and then adsorbed Mn(II) ion is oxidized to insoluble manganese oxide. In addition, manganese oxidation is accelerated by autocatalytic reaction of manganese oxide. The iron and manganese oxides deposited on the surface of the sand and then are aged with coating sand surface.

• 공업화학
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• 제10권3호
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• pp.343-348
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• 1999

저온 공정이 가능한 rf-plasma를 이용한 화학증착법으로 기판의 온도, 출력, $SiH_4$와 천음 함유한 유기화합불 진구체의 희석비 등을 변수로 각 실험 조건에 따라 iron silicide를 제조하였다. 일반적으로 iron silicide 막은 다단계 공정의 Ion Beam Synthesis (IBS)법으로 성장시키고 있으나, 플라즈마를 사용함으로써 단일공정에 의해 $Fe_aSi_bC_cH_d$로 결합된 iron silicide 및 ${\beta}$-상이 형성될 수 있음을 확인하였다. 철 전구체와 실란 (silane)의 희석비에 따라 막 내에 존재하는 탄소와 수소양의 차이로 인해 서로 다른 막의 특성을 나타내었다. 기관의 온도에 따른 광학에너지갭 ($E_b^{opt}$)은 박 표면에 존재하는 수소가 탈착되면서 제공할 수 있는 활성점이 한정되어 있기 때문에 큰 변화가 없었다. 240 watt 이하의 출력에서는 광학에너지갭이 감소하였고, 240 watt 이상의 높은 출력에서는 식각에 의해 미결합수가 증가하여 광학에너지갭은 높게 나타났다.

• 한국식품위생안전성학회지
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• 제9권4호
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• pp.229-235
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• 1994

It is very important to investigate the sanitary chemical conditions of farmwaters used for cattle breeding in the dairy farms. For this purpose we examined pH, KMnO4 consumption, total hardness, chloride, sulfate, NH3-N, NO3-N, fluoride, lead, iron, manganese, cadmium, copper, zinc and chrome in the farmwaters sampled 2 times(spring and summer)in Choongcheongnam and Kangwon Province. The pH of farmwaters in Choongcheongnam and Kangwon Province was 6.49$\pm$0.09, 6.70$\pm$0.06, total hardness 90.21$\pm$7.07, 64.53$\pm$6.38 mg/ι, consumption of KMnO4 4.13$\pm$0.62, 4.34$\pm$0.26mg/ι, NO3-N 6.51$\pm$0.55, 3.61$\pm$0.58 mg/ι, chloride ion 20.51$\pm$1.99, 5.41$\pm$1.36 mg/ι and sulfate ion 6.61$\pm$1.02, 7.28$\pm$1.30 mg/ι, respectively. But NH3-N was scarcely detected. Fluoride, iron, lead, cadmium, zinc, manganese and chrome were not detected from the tested farmwaters. There was high significance between each other in total hardness, NO3-N, chloride ion and sulfate ion. There was regional and seasonal significance in only NO3-N but only regional significance in total hardness and chloride ion.

• 한국균학회지
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• 제21권3호
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• pp.157-164
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• 1993

1. 표고버섯중 광감응성 mitochondrial $F_1-ATPase$는 $Fe^{3+},\;Fe^{2-}$ 및 $Mg^{2+}$ 이온에 의하여 각각 활성화 되었으나 5.0 mM $Fe^{3+}$ 이온에 의한 상대활성도는 대조구에 비하여 107% 증가시켰다. 2 $Mg^{2+}$ 존재하에서 $Fe^{3+}$ 및 $Fe^{2-}$ 각 이온 농도효과는 모두 효소의 활성을 증가시켰으나 0.1 mM $Mg^{2+}$과 5.0 mM $Fe^{3+}$ 이온의 공존하에서 170%를 증가시켜 $Mg^{2+}$ 이온에 의한 상승작용을 보였다. 3. 0.1 mM $Mg^{2+}$와 0.1 mM $Fe^{2+}$ 존재하에서 $Fe^{3+}$ 이온농도효과는 그 농도가 5.0 mM일 때 168%의 활성도 증가를 보여 $Fe^{2-}$ 이온공존효과는 없었다. 4. 이 효소는 $Mg^{2+}$ 및 $Fe^{3+}$ 이온에 의하여 활성화되는 특성을 가지고 있으며 활성금속이온 존재하에서 측정한 최적 pH 빛 온도는 각각 7.5 및 $66^{\circ}C$였다.

• Bulletin of the Korean Chemical Society
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• 제15권6호
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• pp.424-427
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• 1994

Effects of iron compounds in known biomimetic oxidation systems (Gif IV and GoAgg II) have been studied on activity and ketone/alcohol selectivity of cyclohexane oxidation. Both ketone/alcohol ratio and cyclohexane conversion were affected by counter-ion Z of iron compounds Z-Fe. When Z has a more electron withdrawing property, the reactivity is increased and the formation of ketone is favored. From these experimental results, a new mechanism is proposed for the biomimetic oxidation system.

• 청정기술
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• 제30권1호
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• pp.28-36
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• 2024

전기차의 수요가 증가함에 따라 리튬이온전지의 시장 또한 급증하고 있다. 리튬이온전지의 배터리 수명은 제한되어 있으며, 수명을 다한 배터리의 교체 필연적이므로 폐리튬이온전지 배터리가 발생하게 된다. 이에 리튬이온전지 중 폐리튬인산철(LiFePO₄, 이하 LFP라고 함) 양극재 분말에서부터 리튬은 선택적으로 선침출하고 인산철(FePO₄) 분말을 회수하였다. 회수된 인산철 분말은 탄산나트륨(Na₂CO₃) 분말과 혼합하여 열처리하여 그 결정상을 확인하였다. 열처리 온도를 변수로 하였고, 이후 증류수를 이용하여 수침출 후 각 성분의 침출률 및 분말 특성을 비교하였다. 본 연구에서 리튬은 약 100% 침출률을 보였고 800 ℃에서 열처리한 분말의 경우 인이 약 99% 침출되었으며, 침출 잔사는 Fe₂O₃ 단일 결정상으로 확인되었다. 따라서 본 연구에서는 폐LFP 분말로부터 리튬, 인 그리고 철 성분을 개별적으로 분리 및 회수할 수 있었다.