• Title/Summary/Keyword: Metal cations

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Iron Oxide Coated Sand(ICS)의 중금속 흡착제거 특성

  • 최형진;양재규;장윤영
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2003.09a
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    • pp.379-381
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    • 2003
  • Metal sorption onto the ICS (Iron oxide coated sand) was studied in batch experiments. Heavy metal cations such as Cd, Pb, and Cu, and a metal anion, As, which sporadically exist in mine sites, were tested for the sorptive removal by ICS. In low pH conditions As showed the highest removal efficiency compared to the other metal cations. And the sorption removal of As was apparently pH-independent reaction. However, removal of metal cations increased with pH and above pH 7 most metal cations showed very low soluble concentrations after treatment. Such a high removal ratio of metal cations above the neutral pH appeared predominantly due to precipitation.

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Spectral and Thermal Studies of Transition Metal PSSA Ionomers

  • Shim, Il-Wun;Risen, William M. Jr.
    • Bulletin of the Korean Chemical Society
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    • v.9 no.6
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    • pp.368-376
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    • 1988
  • Transition metal PSSA ionomers containing Co(II), Ni(II), Cr(III), Ru(III), and Rh(III) are investigated by IR, Far-IR, UV-Vis and DSC. Reliable IR Spectroscopic criteria are established for assessing the degree of ion-exchange of PSSA ionomers and the local structures around metal cations in them. In the hydrated transition metal PSSA ionomers, the ionic groups are solvated by water molecules and there is no significant interactions between sulfonate group and metal cations. The visible spectra indicated that metal cations are present as [M$(H_2O)_6$]$^{n+}$ with Oh symmetry. Their $T_g$ values increase as the extent of ionic site concentration increases, but there is no direct dependence of $T_g$ on the nature of metal cations or their oxidation states. Thus, the water content in PSSA ionomer is found to have dominant influence on $T_g$ of hydrated transition metal PSSA ionomers. Dehydration of the hydrated transition metal PSSA ionomers results in direct interaction between ionic groups and significant color changes of the ionomers due to the changes of the local structures around metal cations. On the base of spectral data, their local structures are discussed. In case of dehydrated 12.8 and 15.8 mol % transition metal PSSA ionomers, no glass transition is observed in 25-$250^{\circ}C$ region and this is believed to arise from the formation of highly crosslinked structures caused by direct coordination of sulfonate groups of metal cations. In the 6.9 mol % transition metal PSSA ionomers, the glass transition is always observed whether they are hydrated or dehydrated and this is though to be caused by the sufficient segmental mobility of the polymer backbone.

Solvent Extractions of Alkali Metal Cations and Alkaline Earth Cations by Ionizable Crown Ether Phosphonic Acids (이온성 크라운에테르 포스포닉산에 의한 알칼리 금속 양이온과 알칼리 토금속 양이온의 용매추출)

  • Chung, Yeong-Jin
    • Journal of the Korean Applied Science and Technology
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    • v.22 no.1
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    • pp.50-55
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    • 2005
  • A comparison of alkali metal cation and alkaline earth cation solvent extraction was made for three additional monoionizable crown ethers and one diionizable crown ether. sym-(n-Octyldibenzo)-16-crown-5-oxyacetic acid $\underline{1}$ exhibited high efficiency and selecvity in solvent extraction of alkali metal cations with respect to that observed with alkaline earth cations. Sizes of $Na^+$ and $Ca^{2+}$ appropriately match with the cavity size of monoethyl sym-bis[4(5)-tert-butylbenzo]-16-crown-5-oxymethylphosphonic acid $\underline{3}$. As the result, $Na^+$ and $Ca^{2+}$ are the best extracted. sym-(n-Octyldibenzo)-16-crown-5-oxymethyldiphosphonic acid $\underline{4}$was found to be somewhat selective for $Na^+$ over $Li^+$ and other alkaline earth metal cations. In the complexation of alklaine earth cations by crown ether diphosphonic acid $\underline{4}$, $Ca^{2+}$ and $Sr^{2+}$ are the appropriate sizes, but lager $Ba^{2+}$ may be due to favorable formation of a sandwich type complex between the crown ether cavity and the dianion of the deprotonated crown ether phoaphonic acid moiety.

Electrochemical Studies on Ion Recognition of Alkali Metal Cations by 18-crown-6 in Methanol

  • Chi-Woo Lee;Chang-Hyeong Lee;Doo-Soon Shin;Si-Joong Kim
    • Bulletin of the Korean Chemical Society
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    • v.12 no.5
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    • pp.487-490
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    • 1991
  • Electrochemical studies of alkali metal cations $(Na^+, K^+, Rb^+, Cs^+)$ were performed in methanolic solutions of 18-crown-6 and tetrabutylammonium salts at dropping mercury electrodes (DME) and thin mercury film electrodes (TMFE). All the cations investigated were reduced reversibly at DME in the absence and presence of 18-crown-6, and in the latter the limiting currents were decreased and the reduction potentials shifted to the negative direction. The reduction potentials of the metal ions (0.2 mM) in the presence of the crown (10 mM) were - 2.14 $(Na^+)$, - 2.26 $(K^+)$, - 2.20 $(Rb^+) and - 2.14 $(Cs^+)$ V vs. SCE, respectively. The measured potentials were rationalized with ion recognition of the cations by the crown. Electroreduction at TMFE were highly irreversible. A new representation method of ion recognition is presented. In aqueous solutions, electroreduction of the alkali metal ions were characterized by adsorption.

Optical Properties of Metal Halide Perovskite Nanocrystals with Addition of Metal Bromide (금속 브롬화물의 첨가에 따른 금속 할라이드 페로브스카이트 나노결정의 광학적 특성 변화)

  • Yun, Seokjin;Choi, Jihoon
    • Journal of the Korean institute of surface engineering
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    • v.52 no.6
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    • pp.334-341
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    • 2019
  • Organometal halide perovskite materials have attracted much attention in the photovoltaic and light emitting devices due to the compositional flexibility with AMX3 formula (A is an organic amine cation; M is a metal ion; X is a halogen atom). The addition of homovalent or heterovalent metal cations to the bulk organohalide perovskites has been performed to modify their energy band structure and the relevant optoelectronic properties by ligand-assisted ball milling. Here, we report CH3NH3Pb1-xMxBr3 nanocrystals substituted by metallic cations (M is Sn2+, In3+, Bi3+; x = 0, 0.01, 0.02, 0.05, 0.1, 0.2). Photoluminescence and quantum yield was significantly reduced with increasing metallic cations content. These quenching effect could be resulted from the metal cations that behave as a non-radiative recombination center.

Alkali Metal Cation Selectivity of [$1_7$]Ketonand in Methanol: Free Energy Perturbation and Molecular Dynamics Simulation Studies

  • 황선구;장윤희;유진하;정두수
    • Bulletin of the Korean Chemical Society
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    • v.20 no.10
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    • pp.1129-1135
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    • 1999
  • Free energy perturbation and molecular dynamics simulations were carried out to investigate the relative binding affinities of [17] ketonand (1) toward alkali metal cations in methanol. The binding affinities of 1 toward the alkali metal cations were calculated to be in the order Li+ > Na+ > K+ > Rb+ > Cs+, whereas our recent theoretically predicted and experimentally observed binding affinities for [18]starand (2) were in the order K+ > Rb+ > Cs+ > Na+ > Li+. The extremely different affinities of 1 and 2 toward smaller cations, Li + and Na+ , were explained in terms of the differences in their ability to change the conformation to accommodate cations of different sizes. The carbonyl groups constituting the central cavity of 1 can reorganize to form a cavity with the optimal M+ -O distance, even for the smallest Li+, without imposing serious strain on 1. The highest affinity of 1 for Li+ was predominantly due to the highest Coulombic attraction between the smallest Li+ and the carbonyl oxygens of 1.

Fluorescence Intensity Changes for Anthrylazacrown Ethers by Paramagnetic Metal Cations

  • 장정호;김해중;박중희;신영국;정용석
    • Bulletin of the Korean Chemical Society
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    • v.20 no.7
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    • pp.796-800
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    • 1999
  • Three anthrylazacrown ethers in which the anthracene fluorophore π system is separated from the electron donor atoms by one methylene group were synthesized, and their photophysical study was accomplished. These fluorescent compounds showed a maximum fluorescence intensity at pH=5 in aqueous solutions and a decrease in fluorescence intensity upon binding of paramagnetic metal cations (Mn 2+ (d 5 ), Co 2+ (d 7 ), Cu 2+ (d 9 )). The decrease in fluorescence intensity may be attributed to the paramagnetic effect of metal cations to deactivate the excited state by the nonradiative quenching process. The benzylic nitrogen was found to play an important role in changing fluorescence intensity. From the observed linear Stern-Volmer plot and the fluorescence lifetime independence of the presence of metal ions, it was inferred that the chelation enhanced fluorescence quenching (CHEQ) mechanism in the system is a ground state static quenching process. Enhanced fluorescence was also observed when an excess Na + ion was added to the quenched aqueous solution, and it was attributed to cation displacement of a complexed fluorescence quencher.

Solvent Extraction of Alkali Metal and Alkaline Earth Metal Cations Using a Mono-Crown Ether and Bis-(Crown Ether)s (Mono-Crown Ether와 Bis-(Crown Ether)s를 이용한 알칼리금속과 알칼리토금속 양이온들의 용매추출)

  • Shin, Young-Kook;Kim, Hae-Joong
    • Analytical Science and Technology
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    • v.10 no.1
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    • pp.60-65
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    • 1997
  • Solvent extraction of alkali metal and alkaline earth metal cations by mono-crown ether(benzo-15-crown-5) and bis-(crown ether)s(ethylenediamine bis(4'-formyl benzo-15-crown-5)) containing benzo-15-crown-5 moieties were investigated with water-chloroform system at $25^{\circ}C$. The order of the extraction equilibrium constants($K_e$) and the complexation constants($K_c$) for the alkali metal and alkaline earth metal cations with mono-crown ether and bis-(crown ether)s were Ca(II)>Na(I)>Sr(II)>K(I)>Mg(II)>Rb(I) and Sr(II)>Ca(II)>K(I)>Rb(I)>Mg(II)>Na(I) respectively. These results were explained in terms of the size effect of metal cation and electron density effect. Also, the bis-(crown ether)s was found to extract metal cations more effectively than the corresponding mono-crown ether.

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Transport Rate of Transition Metal Cations through a Bulk Liquid Membrane Containing $NtnOenH_4$ and $NdienOenH_4$ as Carriers (운반체로 $NtnOenH_4$$NdienOenH_4$를 포함한 액체막을 통한 전이금속 양이온의 운반속도)

  • Kim, Hae Joong;Chang, Jeong Ho;Shin, Young Kook
    • Journal of the Korean Chemical Society
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    • v.41 no.2
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    • pp.77-81
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    • 1997
  • The transport rates of transition metal cations were increased in order of Ni(II)$(NtnOenH_4)$and 1,12,15-triaza-3,4;9,10-dibenzo-5,8-dioxacyclo-heptadecane$(NdienOenH_4)$as carriers. The transport rates of transition metal cations was found to be of first order to the salt concentrations. It was also found that the dissociation process in the transport process is rate determining step. From the measurements of the transport rates at various temperatures, the partition free energies of hydration$({\Delta}G_p)$for the transition metal cations were calculated. The results showed that the order of transport rates of transition metal cations was found to be proportional to the magnitudes of negative value of the partition free energies of hydration$({\Delta}G_p)$.

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Preparation of a Fluoroionophore Based on Porphyrin-Crown Ether

  • Shin, Eun Ju;Jung, Hyun-Suk
    • Journal of Photoscience
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    • v.11 no.32
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    • pp.83-87
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    • 2004
  • A porphyrin compound containing a crown ether moiety (Por-Crown) and its zinc complex (ZnPor-Crown) have been prepared and the effect of the addition of alkali metal on their fluorescence has been investigated. As alkali metal cations were added, the absorption and fluorescence maxima did not change. However, the absorbance and intensity of fluorescence increased dramatically. Among the alkali metal cations tested, addition of K$^{+}$ and Cs$^{+}$ showed strongest enhancement of absorbance and fluorescence intensity of Por-Crown and ZnPor-Crown.own.

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