• Resources Recycling
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• 제13권4호
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• pp.23-31
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• 2004

Basic studies have been conducted regarding the attempt of the utilization of waste Undaria pinnatifida as an adsorbent for the adsorption treatment of lead-containing wastewater. Undaria pinnatifida was found to be chiefly composed of hyo-carbonaceous compounds and have a fairly high specific surface area, which suggesting the possibility of its application as a Potential adsorbent. The electrokinetic Potential of Undaria pinnatifida particles was observed to be negatively highest at around pH 8 and the fact that its electrokinetic potentials are negative at the whole pH range supported it might be an efficient adsorbent especially for cationic adsorbates. Under the experimental conditions, $Pb^{2+}$ was found to mostly adsorb onto Undaria pinnatifida within a few minutes and reach the equilibrium in adsorption within ca. 30 minutes. The adsorption of $Pb^{2+}$ was exothermic and explained well by e Freundlich model. Acidic pretreatment of Undaria pinnatifida enhanced its adsorption capacity for $Pb^{2+}$ , however, the reverse was observed for alkaline pretreatment. The formation of organometallic complex between $Pb^{2+}$ and some functional groups on the surface of Undaria pinnatifida was considered to be one of the main drives for adsorption. Finally the adsorbability of$ Pb^{2+}$ was examined to be rather affected by several solution features such as the coexistence of other adsorbate, the variation of ionic strength, and the concentration of complexing agent.

• Journal of the Korean Chemical Society
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• 제38권9호
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• pp.621-627
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• 1994

Two crystal structures of dehydrated, $Ag^{+}$ and $Ca^{2+}$-exchanged zeolite A treated at $250^{\circ}C$ with 0.15 torr of Cs vapor have been determined by single-crystal X-ray diffraction technique in the cubic space group $Pm{\bar\3m$ at $21(1)^{\circ}C$ (a = 12.344(2) $\AA$ and 12.304(2) $\AA$). Their structures were refined to the final error indices, R (weighted), of 0.091 with 180 reflections, and 0.093 with 179 reflections, respectively, for which I > $3\sigma(I).$ In each structure, Cs species are found at four different crystallographic sites: 3 $Cs^{+}$ ions per unit cell are located at 8-ring centers, ca. 6.81∼7.14 $Cs^{+}$ ions are found on opposite 6-rings on threefold axes in the large cavity, ca. 1.93∼2.03 $Cs^{+}$ ions are found on threefold axes in the sodalite unit, and 0.53∼0.66 $Cs^{+}$ ions lie on opposite 4-rings. Also, ca. 4.12∼4.27 Ag atoms are located near the center of the large cavity. In these structures, excess cesium atoms in a unit cell are associated with other $Cs^{+}$ ions on a single threefold axis to form the linear cationic cluster $(Cs_4)^{3+}$. By blocking 8-rings, the $Cs^{+}$ ions may have prevented silver atoms from migrating out of the structure. The Ag atoms are likely to have formed hexasilver clusters at the centers of the large cavities. Each hexasilver cluster is stabilized by coordination to 14 $Cs^{+}$ ions.

• Bulletin of the Korean Chemical Society
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• 제16권10호
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• pp.923-929
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• 1995

Four crystal structures of M3-A (M3Na9-xHx-A, M=Rb or K and x=1 or 0), Rb3Na8H-A(a=12.228(1) Å and R1=0.046), Rb3Na9-A (a=12.258(3) Å and R1=0.058), K3Na8H-A (a=12.257(3) Å and R1=0.048) and K3Na9-A (a=12.257(3) Å and R1=0.052), have been determined by single crystal x-ray diffraction technique in the cubic space group Pm3^m at 21 ℃. In all structures, each unit cell contained three M+ ions all located at one crystallographically distinct position on 8-rings. Rb+ ions are 3.12 and 3.21 Å away respectively from O(1) and O(2) oxygens, about 0.40 Å away from the centers of the 8-rings, and K+ ions are 2.87 and 2.81 Å apart from the corresponding oxygens. These distances are the shortest ones among those previously found for the corresoponding ones. Eight 6-rings per unit cell are occupied by eight Na+ ions, each with a distance of 2.31 Å to three O(3) oxygens. The twelfth cation per unit cell is found as Na+ opposite 4-ring in the large cavities of M3Na9-A and assumed to be H+ for M3Na8H-A. With these noble non-framework cationic arrangements, larger M+ ions preferably on all larger 8-rings and the compact Na+ ions on all 6-rings, the bond angles in the 8-rings of M3-A, 145.1 and 161.0 respectively for (Si,Al)-O(1)-(Si,Al) and (Si,Al)-O(2)-(Si,Al), turned out to be remarkably stable and smaller, by more than 12 to 17°, than the corresponding angles found in the crystal structures of zeolites A with high concentration of M+ ions. It is to achieve these remarkably relaxed 8-rings, the main windows for the passage of gas molecules, with simultaneously maximized cavity volumes that M3-A have been selected as one of the efficient zeolite A systems for gas encapsulation.

• Bulletin of the Korean Chemical Society
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• 제14권5호
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• pp.603-610
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• 1993

The crystal structure of dehydrated $Ag_{5.6}K_{6.4}-A$, zeolite A ion-exchanged with $K^+\;and\;Ag^+$ as indicated and dehydrated at 360$^{\circ}$C, has been determined by single-crystal X-ray diffraction techniques. Also determined were the structures of the products of the reactions of this zeolite with 0.1 Torr of Cs vapor at 250$^{\circ}$C for 48 h and 72 h, and with 0.1 Torr of Rb vapor at 250$^{\circ}$C for 24 h. The structures were solved and refined in the cubic space group Pm3m at 21(l)$^{\circ}$C (a= 12.255(l) ${\AA}$ , 12.367(l) ${\AA}$, 12.350(l) ${\AA}$, and 12.263(l) ${\AA}$, respectively). Dehydrated $Ag_{5.6}K_{6.4}$-A was refined to the final error indices $R_1= 0.044\;and\;R_2=0.037$ with 202 reflections for which I>3${\sigma}$(I). The crystal structures of the reaction products were refined to $R_1=0.087\;and\;R_2= 0.089$ with 157 reflections, $R_1=0.080\;and\;R_2= 0.087$ with 161 reflections, and $R_1= 0.071\;and\;R_2=0.061$ with 88 reflections, respectively. In the structure of $Ag_{5.6}K_{6.4}-A,\;K^+$ ions block all 8-oxygen rings, and one reduced Ag atom is found per sodalite cavity. Also, ca. 4.6 $Ag^+ ions\;and\;3.4 K^+ ions$ are found at 6-ring sites in the large cavity. The crystal structures of the reaction products show that all $K^+$ and $Ag^+$ ions have been reduced, and that all K^+$ atoms have left the zeolite. Cs or Rb species are found at three different crystallographic sites: 3.0 $Cs^+\;or\;3.0Rb^+$ ions per unit cell occupy 8-ring centers, ca. 8.0 $Cs^+ ions\;or\;5.7 Rb^+$ ions, are found on threefold axes opposite 6-rings deep in the large cavity, and ca. 2.5 $Cs^+\;or\;2.3 Rb^+ ions are found on threefold axes in the sodalite unit. Also, 1 $Rb^+$ ion lies opposite a 4-ring. Silver atoms, corresponding to 75% or 40% occupancy of hexasilver clusters stabilized by coordination to $Cs^+\;or\;Rb^+$ ions, are found at the centers of the large cavities. In the crystal structures of dehydrated Ag_{5.6}K_{6.4}-A$ reacted with Cs vapor, excess Cs atoms are absorbed and these form (locally) cationic clusters such as $(Cs_4)3^+\;and\;(Cs_6)4^+$.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권11호
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• pp.24-30
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• 2018

Various investigations of vegetable oil extracted from natural resources are underway because of their low cost and environmental value. On the other hand, the double bonds in vegetable oil should be substituted to other high reactive functional groups due to their low reactivity for synthesizing bio-polymeric materials. ${\alpha}$-eleostearic acid, which consists of a conjugated triene, is the main component of tung oil, and the conjugated triene allows tung oil to have higher reactivity than other vegetable oils. In this study, tung oil was copolymerized with styrene and divinylbenzene to make a thermoset resin without any substitution of functional groups. The thermal and mechanical properties were measured to examine the effects of the composition of each monomer on the synthesized thermoset resin. The results showed that the products have only one Tg, which means the synthesized thermoset resins are homogeneous at the molecular level. The mechanical properties show that tung oil acts as a soft segment in the copolymer and makes a more elastic product. On the other hand, divinylbenzene acts as a hard segment and makes a more brittle product.

• Applied Chemistry for Engineering
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• 제22권2호
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• pp.173-177
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• 2011

In this study, the formation of $AlPO_4$-type porous materials from alum sludge was investigated. The materials were synthesized by the reaction of aluminum hydroxide and phosphoric acid with an organic template. Cationic surfactant, natural humic acid, and amino acids were used for the organic template. The residual organic templates were removed by calcination at $600^{\circ}C$ in the air. Powder X-ray diffraction patterns showed the charicteristic patterns of the $AlPO_4$-type porous materials. The morphology of the material was examined using a scanning electron microscopy. The coordination environment of $Al^{3+}$ ion was investigated by $^{27}Al$ MAS NMR technique. Both tetrahedrally and octahedrally coordinated$Al^{3+}$ ions were found in the as-synthesized samples while all $Al^{3+}$ ions were tetrahedrally coordinated in the calcined products. The development of mesopore in the solid material was confirmed by the measurement of BET specific surface area. Finally, they were used for removal of toxic formaldehyde from the air and the formaldehyde molecules were adsorbed on the surface of pores. In conclusion, $AlPO_4$-type porous materials from alum sludge might be applicable in the removal of toxic volatile organic compounds from the air.

• The Korea Journal of Herbology
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• 제27권6호
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• pp.37-42
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• 2012

Objectives : Angelica Gigantis Radix is prescribed as the root of different Angelica species on the pharmacopoeia in Korea, Japan and China. Chemical components and their biological activities were also different according to their species. A study for the development of simple method to compare Angelica roots was needed. In order to classify them, the methods such as DNA sequencing analysis and taste sensor were applied to three Angelica species like Angelica gigas, Angelica acutiloba and Angelica sinensis. Methods : PCR amplification of intergenic transcribed spacer (ITS) region was performed using ITS1 and ITS4 primer from nine Angelica roots, and then nucleotide sequence was determined. Taste pattern of samples were measured using the taste-sensing system SA402B equipped with a sensing unit, which consists of artificial lipid membrane sensor probes of anionic bitterness, astringency, saltiness, umami, and cationic bitterness (C00, AE1, CT0, AAE, and AN0, respectively). Results : As a result of comparing the similarity of the ITS region sequences, A. sinensis was discriminated from the others (A. gigas and A. acutiloba). Equally this genetic result, A. gigas and A. acutiloba showed similar taste pattern as compared to A. sinensis. Sourness, bitterness, aftertaste of bitterness, astringency, and aftertaste of astringency of A. sinensis were significantly high as compared with A. gigas and A. acutiloba. In contrast, richness was significantly low. Conclusions : These taste pattern can be used as a way of comparison of Angelica species and this technic could be applied to establish a taste pattern marker for standardization of herbs in various purposes.

• Clean Technology
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• 제15권1호
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• pp.47-53
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• 2009

Mesoporous aluminas (A-C, A-A, and A-N) were prepared by a templating method using cationic(C), anionic(A), and non-ionic(N) surfactant as a structure-directing agent, respectively. Nickel catalysts supported on mesoporous alumina (Ni/A-C, Ni/A-A, and Ni/A-N) were then prepared by an impregnation method, and were applied to hydrogen production by steam reforming of liquefied natural gas (LNG). Regardless of surfactant type, nickel species were finely dispersed on the surface of mesoporous alumina in the calcined catalysts. It was revealed that interaction between nickel species and support in the reduced catalysts was strongly dependent on the identity of surfactant. LNG conversion and $H_2$ composition in dry gas increased in the order of Ni/A-C < Ni/A-A < Ni/A-N. It was found that catalytic performance increased with increasing nickel surface area in the reduced catalyst. Among the catalyst tested, Ni/A-N catalyst with the highest nickel surface area showed the best catalytic performance.

• Journal of the Korean Electrochemical Society
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• 제26권4호
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• pp.43-55
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• 2023

Mass transport through nanoporous structures such as nanopores or nanochannels has fundamental electrochemical implications and many potential applications as well. These structures can be particularly useful for water treatment, energy conversion, biosensing, and controlled delivery of substances. Earlier research focused on creating nanopores with diameters ranging from tens to hundreds of nanometers that can selectively transport cationic or anionic charged species. However, recent studies have shown that nanopores with diameters of a few nanometers or even less can achieve more complex and versatile transport control. For example, nanopores that mimic biological channels can be functionalized with specific receptors to detect viruses, small molecules, and even ions, or can be made hydrophobic and responsive to external stimuli, such as light and electric field, to act as efficient valves. This review summarizes the latest developments in nanopore-based systems that can control mass transport based on the size of the nanopores (e.g., length, diameter, and shape) and the physical/chemical properties of their inner surfaces. It also provides some examples of practical applications of these systems.

• Journal of the Korean Electrochemical Society
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• 제26권4호
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• pp.71-79
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• 2023

In this study, we employed anionic, cationic, and nonionic surfactants for the hydrophilization of porous substrates used in the fabrication of pore-filling membranes. We investigated the extent of hydrophilization based on the type of surfactant, its concentration, and immersion time. Furthermore, we used the hydrophilized substrates to produce pore-filling anion exchange membranes and compared their ion conductivity to determine the optimal hydrophilization conditions. For the ionic surfactants used in this study, we observed that hydrophilization progressed rapidly from the beginning of immersion when the applied concentration was 3.0 wt%, compared to lower concentrations (0.05, 0.5, and 1.0 wt%). In contrast, for the relatively larger molecular weight non-ionic surfactants, smooth hydrophilization was not observed. There was no apparent correlation between the degree of hydrophilization and the ion conductivity of the anion exchange membrane. This discrepancy suggests that an excessive hydrophilization process during the treatment of porous substrates leads to excessive adsorption of the surfactant on the sparse surfaces of the porous substrate, resulting in a significant reduction in porosity and subsequently decreasing the content of polymer electrolyte capable of ion exchange, thereby greatly increasing the electrical resistance of the membrane.