• Nuclear Engineering and Technology
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• 제32권5호
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• pp.504-513
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• 2000

The adsorption characteristics of methyl iodide generated from the simulated off-gas stream on various adsorbents such as silver ion-exchanged zeolite (AgX), zeocarbon and activated carbon were investigated. An extensive evaluation was made on the optimal silver ion-exchanged level for the effective removal of methyl iodide at temperature up to 38$0^{\circ}C$. The degree of adsorption efficiency of methyl iodide on silver ion-exchanged zeolite is strongly dependent of silver ion-amount and process temperature. The influence of temperature, methyl iodide concentration and silver ion-exchanged level on the adsorption efficiency is closely related to the pore characteristics of adsorbents. It would be facts that the effective silver ion-exchanged level was about 10 wt%, based on the degree of silver utilization for the removal of methyl iodide.

• 한국환경과학회지
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• 제13권1호
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• pp.89-97
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• 2004

An author has been known that A-type zeolite supported with silver ions has excellent antibacterial activity. However, it is no research of concern in the antibacterial activity of eluted silver ions. This study tested the elution of silver ions from A-type zeolite silver ions in deionized distilled water and NaNO$_3$ aqueous solution. In NaNO$_3$ aqueous solution of 74mM to 588mM, it was found that the concentration of silver ions and electric conductivity increased with the increasing concentration of sodium ions, and equilibrated at 15 min, and the ion exchange equilibrium coefficient, k, is 1.3${\times}$10$\^$-3/. However, deionized distilled water is not equilibrated to pass 6 months. A-type zeolite sodium ions showed no antibacterial activity. It was found that antibacterial activity was exhibited even at the concentration of 10 nM of eluted silver ions, and E-coli died with the incorporation of 2.43${\times}$10$\^$8/ Ag ion/cell. antibacterial activity of A-type zeolite silver ions were mainly attributed to hydroxyl radical.

• 대한환경공학회지
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• 제22권10호
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• pp.1765-1775
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• 2000

원자력시설의 고온공정에서 발생되는 방사성요오드를 제거하기 위하여 은이온 교환 합성제을 라이트를 사용하고 있는데, 담체로 사용되는 고가의 합성제올라이트 대신에 천연제올라이트를 이용하기 위한 기초연구를 수행하였다. 천연제올라이트를 NaCl 및 $NaNO_3$용액으로 전처리한 후 표면개질에 따른 표면 및 물리적 특성을 XRD, SEM-EDAX 및 BET 분석을 통하여 분석하였다. 아울러 표면개질된 천연제올라이트의 은이온 교환 특성을 $150^{\circ}C$에서 메틸요오드 흡착성능과 연관시켜 분석하였으며, 1 N $NaNO_3$ 용액으로 표면개질한 후 1.2N $AgNO_3$로 은이온교환한 경우가 가장 적합한 것으로 나타났다. 표면개질 은이온교환 천연제올라이트(Ag-SMNZ)를 이용하여 온도범위 $100{\sim}300^{\circ}C$에서 등온흡착실험을 수행한 결과, 13X의 흡착성능과 거의 비슷한 결과를 보여주었고, 은이온교환 합성제올라이트(AgX)의 최대 흡착성능과 비교하여 약 50%에 근접한 것으로 나타났다. 또한 $150^{\circ}C$와 $200^{\circ}C$에서 약간 높은 흡착성능을 가지며 탈착후 잔존량을 통해 이 온도영역에서 강한 화학흡착이 일어남을 추측할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제8권2호
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• pp.69-72
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• 1987

The structures of dehydrated $Ag_9Cs_3$-A treated with hydrogen gas at three different temperatures have been determined by single-crystal X-ray diffraction techniques. Their structures were solved and refined in the cubic space group Pm3m at 23(1) $^{\circ}C$. All crystals were ion exchanged in flowing streams of aqueous $AgNO_3$/$CsNO_3$ with a mole ratio 1:3.0 to achieve the desired crystal composition. The structures treated with hydrogen at $23^{\circ}C(a=12.288(1)\;{\AA})\;and\;310^{\circ}C(a=12.291(2)\;{\AA})$ refined to the final error indices R1 = 0.091 and R2 = 0.079, and 0.065 and 0.073, respectively, using the 216 and 227 reflections, respectively, for which I >3${\sigma}$(I). In both of these structures, eight $Ag^+$ ions are found nearly at 6-ring centers, and three $Cs^+$ ions lie at the centers of the 8-rings at sites of $D_{4h}$ symmetry. One $Ag^{\circ}atom$, presumably formed from the reduction of a $Ag^+$ ion by an oxide ion of a residual water molecule or of the zeolite framework during the dehydration process, is retained within the zeolite, perhaps in a cluster. In these two structures hydrogen gas could not enter the zeolite to reduce the $Ag^+$ ions because the large $Cs^+$ ions blocked all the 8-windows. However, hydrogen could slowly diffuse into the zeolite and was able to reach and to reduce about half of the $Ag^+$ ions in the structure only at high temperature ($470^{\circ}C$). The silver atoms produced migrated out of the zeolite framework, and the protons generated led to substantial crystal damage.

• Bulletin of the Korean Chemical Society
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• 제6권4호
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• pp.202-206
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• 1985

The crystal structure of The crystal structure of $Ag^+$-Exchanged Zeolite A, $Ag_{4.6}Na_{7.4}-A$, dehydrated, treated with $H_2$, and evacuated, all at $350^{\circ}C$, has been determined by single crystal x-ray diffraction methods in the cubic space group Pm3m at $24(1)^{\circ}C;$ a = $12.208(2)\AA.$ The structure was refined to the final error indices R1 = 0.088 and R2 (weighted) = 0.069 using 194 independent reflections for which II_0$ > $3{\sigma}(I_0)$. On threefold axes near the centers of 6-oxygen rings, $7.4 Na^+$ ions and $0.6 Ag^+$ ions are found. Two non-equivalent 8-ring $Ag^+$ ions are found off the 8-ring planes, each containing about $0.6 Ag^+$ ions. Three non-equivalent Ag atom positions are found in the large cavity, each containing about 0.6 Ag atoms. This crystallographic analysis may be interpreted to indicate that $0.6 (Ag_6)^{3+}$ clusters are present in each large cavity. This cluster may be viewed as a nearly linear trisilver molecule $(Ag_3)^0$ (bond lengths, 2.92 and 2.94 $\AA;$ angle, $153^{\circ})$ stabilized by the coordination of each atom to a Ag^+$ ion at 3.30, 3.33, and 3.43 $\AA$, respectively. In addition, one of the silver atoms approaches all of the 0(1) oxygens of a 4-ring at $2.76\AA.$ Altogether $7.4 Na^+$ ions, $1.8 Ag^+$ ions, and 1.8 Ag atoms are located per unit cell. The remaining $1.0 Ag^+$ ion has been reduced and has migrated out of the zeolite framework to form silver crystallites on the surface of the zeolite single crystal.

• Food Science and Biotechnology
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• 제17권2호
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• pp.330-335
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• 2008

Water vapor adsorption kinetics of 3 different types of chitosan-based films, i.e., control chitosan, chitosan/montmorillionite (Na-MMT), and chitosan/silver-zeolite (Ag-Ion) nanocomposite films, were investigated at temperature range of $10-40^{\circ}C$. In all the films, water vapor is initially adsorbed rapidly and then it comes slowly to reach equilibrium condition. Reasonably good straight lines were obtained with plotting of 1/($m-m_0$) vs. l/t. It was found that water vapor adsorption kinetics of chitosan-based films was accurately described by a simple empirical model and the rate constant of the model followed temperature dependence according to Arrhenius equation. Arrhenius kinetic parameters ($E_a$ and $k_o$) for water vapor adsorption by chitosan-based films showed a kinetic compensation effect between the parameters with the isokinetic temperature of 315.52 K.

• Bulletin of the Korean Chemical Society
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• 제7권3호
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• pp.190-193
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• 1986

The structure of partially $Ag^+$-exchanged zeolite 4A, $Ag_{7.6}Na_{4.4}-A$, vacuum dehydrated at $370^{\circ}C$, has been determined by single-crystal x-ray diffraction techniques in the cubic space group, Pm3m (a = 12.311(1)${\AA}$) at $24(1)^{\circ}}C$. The structure was refined to the final error indices $R_1$ = $R_2$ (weighted) = 0.064 using 266 independent reflections for which $I_0$>$3{\sigma}(I_0)$. Three $Na^+$ ions occupy the 3 8-ring sites, and the remaining ions, 1.4 $Na^+$ and 6.6 $Ag^+$, fill the 8 6-ring sites; each $Ag^+$ ion is nearly in the [111] plane of its 3 O(3) ligands, and each $Na^+$ ion is 0.9${\AA}$ from its corresponding plane, on the large-cavity side. One reduced silver atom per unit cell was found inside the sodalite unit. It was presumably formed from the reduction of a $Ag^+$ ion by an oxide ion of a residual water molecule or of the zeolite framework. It may be present as a hexasilver cluster in 1/6 of the sodalite units, or, most attractively among several alternatives, as an isolated Ag atom coordinated to 4 Ag ions in each sodalite unit to give $(Ag_5)^{4+}$, symmetry 4mm.

• 한국재료학회지
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• 제11권2호
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• pp.120-125
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• 2001

흡착재료에는 hydroxyapatite(HAp), zeolite,, 분자체탄소, 활성탄, 알루미나등의 재료가 많이 사용되고 있다. 이들 흡착재료 중에서 금속이온과 양이온 교환반응이 좋은 HAp, zeolite는 폐수처리과정에서 많이 사용되고 있지만, 피러나 이 폐수처리과정에서 문제되는 것은 유해한 중금속뿐만 아니라 많은 세균들이 이 폐수에 존재하고 있어 수질오염 등의 여러 가지 문제를 야기 시키고 있다. 본 연구는 여러 중금속 흡착재료 중에서 HAp, zeolite에 항균효과가 있다고 알려진 금속이온 (Ag$^{+}$, Cu$^{2+}$, $Zn^{2+}$)들을 이온 치환시켜 항균성을 흡착재료에 부여하고자 한다. HAp, zeolite에 Ag$^{+}$, Cu$^{2+}$, $Zn^{2+}$의 금속이온들을 치환시킨 후, E. Coli로 항균효과를 측정하였다. HAp, zeolite와 여러 금속이온 치환후의 항균효과를 측정한 결과, Ag$^{+}$ 로 이온치환 시킨 HAp, zeolite에서는 1$\times$$10^{-2}$cell/ml 농도의 E. Coli에서 24시간가지 완벽한 항균효과를 보였고, Cu$^{2+}$와 $Zn^{2+}$으로 이온치환 시킨 경우에서는 좋은 항균효과를 보이지 않았다. 이러한 결과는 Feng. et. al.이 발표한 바와 같이1) Ag ion이 cell내부의 DNA에 영향을 기척, 복제능력을 떨어뜨리고 Cell을 비활성화 시키기 때문이다.

• Bulletin of the Korean Chemical Society
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• 제9권5호
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• pp.303-308
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• 1988

Four crystal structures of dehydrated Ag(I) and Tl(I) exchanged zeolite A, $Ag_{12-x}Tl_x$-A, x = 2, 3, 4, and 5, have been determined by single-crystal x-ray diffraction techniques. Their structures were solved and refined in the cubic space group Pm3m at $21(1)^{\circ}C$. All crystals were ion exchanged in flowing streams of mixed $AgNO_3\;and\;TlNO_3$ aqueous solution, followed by dehydration at $350^{\circ}C$ and $2{\times}10^{-6}$ Torr for 2 days. In all of these structures, one-sixth of the sodalite units contain octahedral hexasilver clusters at their centers and eight $Ag^+$ ions are found on threefold axes, each nearly at the center of a 6-oxygen ring. The hexasilver cluster is stabilized by coordination to eight $Ag^+$ ions. The Ag-Ag distance in the cluster, ca. 2.92 ${\AA}$, is near the 2.89 ${\AA}$ bond length in silver metal. The remaining five-sixths of the sodalite units are empty of silver species. The first three $Tl^+$ ions per unit cell preferentially associate with 8-oxygen rings, and additional $Tl^+$ ions, if present, are found on threefold axes in the large cavity.

• 한국포장학회:학술대회논문집
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• 한국포장학회 2006년도 정기총회 및 추계학술발표대회
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• pp.54-73
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• 2006

Four different types of chitosan-based nanocomposite films were prepared using a solvent casting method by incorporating with four types of nanoparticles, i.e., an unmodified montmorillonite (Na-MMT), an organically modified montmorillonite (Cloisite 30B), a Nano-silver, and a Ag-zeolite (Ag-Ion). X-ray diffraction patterns of the nanocomposite films indicated that a certain degree of intercalation was formed in the nanocomposite films, with the highest intercalation in the Na-MMT-incorporated films followed by films with Cloisite 30B and Ag-Ion. SEM micrographs showed that in all the nanocomposite films, except the Nanosilver-incorporated one, nanoparticles were dispersed homogeneously throughout the chitosan polymer matrix. Consequently, mechanical and barrier properties of chitosan films were affected through intercalation of nanoparticles, i.e., tensile strength (TS) increased by 7-16%, while water vapor permeability (WVP) decreased by 25-30% depending on the nanoparticle material tested. In addition, chitosan-based nanocomposite films, especially silver-containing ones, showed a promising range of antimicrobial activity.