• 산업기술연구
• /
• 제33권A호
• /
• pp.89-92
• /
• 2013

The characteristics of floc formation of the iron(Fe) ions was studied for developing the process treating the acid mine drainage. The metal ions in aqueous solution oxidized with oxygen in air, which generated hydrogen ion and lowered the pH of the aqueous solution. The iron(Fe) ions were formed into flocs by the acid-base reaction with the added $Ca(OH)_2$ for the neutralizing the solution. There were several variables affecting the formation, size and color of floc; whether air was present or not, air feeding rate, oxidizing time, concentration of $Ca(OH)_2$, the acid-base reaction time of the $iron(Fe)-Ca(OH)_2$. For proper formation of the $iron(Fe)-Ca(OH)_2$ flocs and developing the floc treating system, the control variables mentioned above should be considered.

• Transactions on Electrical and Electronic Materials
• /
• 제15권6호
• /
• pp.320-323
• /
• 2014

Ga-doped $LiFePO_4$ cathode materials were synthesized using a hydrothermal method. The microstructural characteristics and electrochemical performances were systematically investigated using field emission scanning electron microscopy, high-resolution X-ray diffraction, energy dispersive X-ray spectroscopy, charge-discharge cycling, cyclic voltammetry, and electrochemical impedance spectroscopy. Among the as-prepared samples, $LiFe_{0.96}Ga_{0.04}PO_4$ demonstrates the best electrochemical properties in terms of discharge capacity, electrochemical reversibility, and cycling performance with an initial discharge capacity of $125mAh\;g^{-1}$ and high lithium ion diffusion coefficient of $1.38{\times}10^{-14}cm^2s^{-1}$ (whereas for $LiFePO_4$, these were $113mAh\;g^{-1}$ and $8.09{\times}10^{-15}cm^2\;s^{-1}$, respectively). The improved electrochemical performance can be attributed to the facilitation of Li+ ion effective diffusion induced by $Ga^{3+}$ substitution.

• 한국환경과학회지
• /
• 제9권1호
• /
• pp.43-47
• /
• 2000

A study on the remediation of heavily for ion contaminated soils from abandoned iron mine was carried out, using ex-situ extraction process. Also, oxalic acid as a complex agent was evaluated as a function of concentration, reaction time and mixing ratio of washing agent in order to evaluate Fe removability of the soil contaminated from the abandoned iron mine. Oxalic acid showed a better extraction performance than 0.1N-HCl, i.e., the concentrations of Fe ion extracted from the abandoned mine for the former at uncontrolled pH and the latter were 1,750 ppm and 1,079 ppm, respectively. The optimum washing condition of oxalic acid was in the ratio of 1:5 and 1:10 between soil and acid solution during l hr reaction. The total concentrations of Fe ion by oxalic acid and EDTA at three repeated extraction, were 4,554 ppm and 864 ppm, respectively. The recovery of Fe ions from washing solution was achieved, forming hydroxide precipitation and metal sulfide under excess of calcium hydroxide and sodium sulfide. In addition, the amounted of sodium sulfide and calcium hydroxide for the optimal revovery of Fe were 15g/$\ell$ and 5g/$\ell$ from the oxalic acid complexes, respectively.

• Bulletin of the Korean Chemical Society
• /
• 제21권4호
• /
• pp.393-400
• /
• 2000

2,2￠-Dihydroxyazobenzene (DHAB) was attached to poly(ethylenimine) (PEI) to obtain DHAB-PEI. Spectral titration revealed that uranyl, Fe(III), Cu(II), and Zn(II) ion form 1 : 1-type complexes with DHAB attached to PEI. Formation constants for the metal complexes formed by the DHAB moieties of DHAB-PEI were mea-sured by using various competing ligands. The results indicated thatthe concentrations of uranyl, Fe(III), and Cu(II) ions can be reduced to 10 -16 -10 -23 M at p 8 with DHAB-PEI when the concentration of the DHAB moiety is 1 residue M. By using cyanuric chloride as the coupling reagent, DHAB-PEI was immobilized on Sephadex G-25 resin to obtain DHAB-PEI-Seph. Binding of uranyl,Fe(III), Cu(II), and Zn(II) ion by DHAB-PEI-Seph was characterized by using competing ligands. A new method has been developed for characteriza-tion of metal sequestering ability of a chelating resin. Formation constants and metal-binding capacity of two sets of binding sites on the resin were estimated for each metal ion. DHAB-PI-Seph was applied to recovery of metals such as uranium,Fe, Cu, Zn, Pb, V, Mn, and W from seawater. The uranium recovery from seawaterby DHAB-PEI-Seph does not meet the criterion for economical feasibility partlydue to interference by Fe and Zn ions. The seawater used in the experiment was contaminated by Fe and Zn and, therefore, the efficiency of uranium extractionfrom seawater with DHAB-PEI-Seph could be improved if the experiment is carried out in a cleaner sea.

• Journal of Magnetics
• /
• 제12권2호
• /
• pp.81-83
• /
• 2007

Etching of NiFe films covered with an organic photo-resist or Ti was successfully performed by an inductively coupled plasma-reactive ion etching (ICP-RIE) system using $CHF_3/O_2/NH_3$ discharges exchanging $CHF_3$ for $CH_4$ gas gradually. Experimental results showed that the organic photo-resist mask can be applied to the NiFe etching. In the case of the Ti metal mask, it was found that the etching-selectivity Ti against NiFe was significantly varied from 7.3 to ${\sim}0$ by changing $CHF_3/CH_4/O_2/NH_3$ to $CH_4/O_2/NH_3$ discharges used in the ICP-RIE system. These results show that the present RIE of NiFe was dominated by a chemical reaction rather than a physical sputtering.

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

• Bulletin of the Korean Chemical Society
• /
• 제18권7호
• /
• pp.743-749
• /
• 1997

Local structure refinement of the BaFe1-xSnxO3-y system (x=0.00-0.50) has been carried out with Fe K-edge x-ray absorpion spectroscopic studies. It is found out that the Fe ions are placed in two different symmetric sites such as tetrahedral and octahedral sites in the compounds by comparison with Fe K-edge x-ray absorption near edge structure (XANES) spectrum of the γ-Fe2O3 compound as a reference. Small absorption peaks of dipole-forbiden transitions appear at a pre-edge region of 7111 eV due to the existence of Fe ions in the tetrahedral and octahedral sites. The peak intensity decreases with the substitution amount of Sn ion. Three different absorption peaks of 1s→4p dipole-allowed transition appear on the energy region between 7123 and 7131 eV. The peaks correspond to 1s→4p main transition of Fe ions in tetrahedral and octahedral sites and 1s→4p transition followed by the shakedown process of ligand to metal charge transfer. The bond distances between Fe ions in the tetrahedral site and nearest neighboring oxygen atom (Fe-4O), and those in octahedral site (Fe-6O) are determined with the extended x-ray absorption fine structure (EXAFS) analysis. Two different interatomic distances increase with the substitution amount of Sn ion and also the bond lengths of Fe-4O are shorter than those of Fe-6O in all compounds.

• 한국자기학회지
• /
• 제15권3호
• /
• pp.177-180
• /
• 2005

Czochralski방법을 사용하여 정비조성(stoichiometric)으로 성장시킨 강유전체 $LiTaO_3$, 단결정을 $1000^{\circ}C$ 및 $1100^{\circ}C$에서 각각 열처리하였다. 열처리한 시료와 열처리하지 않은 정비조성 $LiTaO_3$ 단결정에 대하여 전자 상자성 공명(EPR : electron paramagnetic resonance) 실험을 하였다. X-band(9.21 GHz) 전자 상자성 공명 스펙트로미터를 사용하여 얻은 $Fe^{3+}$ 상자성 불순물 이온의 공명 흡수선을 분석한 결과 정비조성 $LiTaO_3$ 단결정내의 $Fe^{3+}$ 상자성 불순물 이온의 위치(site location)와 국소 대칭성(local site symmetry)은 열처리 후에도 변화가 없는 것을 알 수 있었다. 그러나 $1000^{\circ}C$및 $1100^{\circ}C$에서 열처리 한 단결정의 경우에는 $v$ 이온이 $Fe^{2+}$ 이온으로 원자가 상태가 바뀌는 것을 화인 하였다. 또한 유효 스핀 하밀토니안을 이용하여 EPR 상수를 계산하였다.

• 대한화학회지
• /
• 제47권2호
• /
• pp.115-120
• /
• 2003

Perfluorinated sulfonated polymer(Nafion)-ethylenediamine(en)이 화학수식된 유리탄소전극으로 Fe(II) 이온의 정량에 대해 연구하였다. Fe(II) 이온의 착화제인 en을 nafion에 고정시켜 유리탄소전극 표면에 수식하면 이 수식전극의 en은 Fe(II) 이온과 $[Fe(en)_3]^{+2}$의 착물을 형성한다. Nafion-en이 화학수식된 유리탄소전극에서 시차펄스전압전류법에 의한 Fe(II) 이온의 산화봉우리전위는 0.340${\pm}$0.015 V(vs. Ag/AgCl), 측정범위는 $5{\times}10^{-6}{\sim}0.2{\times}10^{-3} M(0.28{\sim}11.17 mg/L)$, 검출한계(3s)는 $1.89{\times}10^{-5}$M(1.056 mg/L)이었다.

• 약학회지
• /
• 제13권1호
• /
• pp.28-32
• /
• 1969

For the colorimetric determination of Sulfa-drugs by means of solvent extraction, the sample solutions were added into dimethylglyoxime-Fe(II) complex solution, and extracted with pyridine-chloroform mixture (1:50) is a range of pH 7.5-8.5. The extracted solution shows stability and maximum absorption at 402m${\mu}$.