• Bulletin of the Korean Chemical Society
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• v.11 no.5
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• pp.411-415
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• 1990

The dabsylation of amino acids has been applied to resolve their optical isomers with the use of chiral mobile phase in high performance liquid chromatography. The dabsyl amino acids were successfully separated on reversed phase column($C_{18}$) by adding a chiral L-benzylproline-Cu(II) chelate to the mobile phase. The separation selectivity of the dabsyl amino acid enantiomers was not less than that of dansyl amino acids. The retention order of the dabsyl amino acid enantiomers was as those of the dansyl amino acid enantiomers except dabsyl threonine. The optical selectivity of the dabsyl amino acids increase with pH of the mobile phase and concentration of the chelate, but slightly decreases with concentration of buffer and organic solvent composition. However serine, methionine, valine, and leucine showed a slight decrease in the optical selectivity with increase in pH. The retention times of the dabsyl amino acids decreases with increasing pH and acetonitrile concentration but increases with the concentration of the chiral chelate added. The mechanism of the optical resolution is based on a stereospecific interaction including a intramolecular hydrophobic effect and SN-2 reactivity of the ligand exchange chromatography.It is advantageous to detect absorption at 436 nm, which is less interferent them the other detection systems. The derivatized dabsyl amino acids are stable for a month.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.12
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• pp.37-42
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• 1999

In this paper, some of main processes for the next generation integrated circuits, such as Cu damascene process using CMP, electron beam lithography, $SiO_2$ CVD and RIE, Ti/Cu-CVD were carried cut and then, two level Cu interconnects were accomplished. In the results of CMP unit processes, a 4,635 ${\AA}$/min of removal rate, a selectivity of Cu : $SiO_2$ of 150:1, a uniformity of 4.0% are obtained under process conditions of a head pressure of 4 PSI, table and head speed of 25rpm, a oscillation distance of 40 mm, and a slurry flow rate of 40 ml/min. Also 0.18 ${\mu}m\;SiO_2$ via-line patterns are fabricated using 1000 ${\mu}C/cm^2$ dose, 6 minute and 30 second development time and 1 minute and 30 second etching time. And finally sub-0.2 ${\mu}$ twolevel metal interconnects using the developed processes were fabricated and the problems of multilevel interconnects are discussed.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.269-273
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• 2003

The synthesis and properties of 2,13-bis(3'-pyridylmethyl) $(L^3)$, 2,13-bis(4'-pyridylmethyl) $(L^4)$, and 2,13-bis(phenylmethyl) $(L^5)$ derivatives of 5,16-dimethyl-2,6,13,17-tetraazatrcyclo$[16.4.0.^{1.18}0^{7.12}]$docosane are reported. The 3- or 4-pyridylmethyl groups of $[ML^3](ClO_4)_2\;or\;[ML^4](ClO_4)_2$ (M = Ni(Ⅱ) or Cu(Ⅱ)) are not involved in coordination, and the coordination geometry (square-planar) and ligand field strength of the complexes are quite similar to those of $[ML^5](ClO_4)_2$, bearing two phenylmethyl pendant arms. However, the complex formation reactions of $L^3\;and\;L^4$ are strongly influenced by the pyridyl groups, which can interact with a proton or metal ion outside the macrocyclic ring. The macrocycle $L^5$ exhibits a high copper(Ⅱ) ion selectivity against nickel(Ⅱ) ion; the ligand readily reacts with copper(Ⅱ) ion to form $[CuL^5]^{2+}$ but does not react with hydrated nickel(Ⅱ) ion in methanol solutions. On the other hand, $L^3\;and\;L^4$ form their copper(Ⅱ) and nickel(Ⅱ) complexes under a similar condition, without showing any considerable metal ion selectivity. The ligands $L^3\;and\;L^4$ react with copper(Ⅱ) ion more rapidly than does $L^5$ at pH 6.4. At pH 5.0, however, the reaction rate of the former macrocycles is slower than that of the latter. The effects of the 3- or 4-pyridylmethyl pendant arms on the complex formation reaction of $L^3\;and\;L^4$ are discussed.

• Journal of environmental and Sanitary engineering
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• v.21 no.3 s.61
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• pp.52-60
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• 2006

The ion exchange resins have been synthesized from chlormethyl styrene-1,4-divinylbenzene(DVB) with 1%, 2%, and 20%-crosslinking and macrocyclic ligand of cryptand 21 by copolymerization method and the adsorption characteristics of uranium(VI), copper(II) and dysprosium(III) metallic ions have been investigated in various experimental conditions. The synthesis of these resins was confirmed by content of chlorine, element analysis, and IR-spectrum. The effects of pH, equilibrium time, dielectric constant of solvent and crosslink on adsorption of metallic ions were investigated. The metal ion was showed fast adsorption on the resins above pH 3. The optimum equilibrium time for adsorption of metallic ions was about two hours. The adsorption selectivity determined in ethanol was in increasing order uranium$(UO^{2+}_2)\;>\;copper(Cu^{2+})\;>\;dysprosium(Dy^{3+})$ ion. The adsorption was in order of 1%, 2%, and 20% crosslink resin and adsorption of resin decreased in proportion to order of dielectric constant of solvents.

• Clean Technology
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• v.13 no.4
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• pp.287-292
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• 2007

[ $M/Al_2O_3$ ] (M = Mn, Fe, Co, Ni, Cu) catalysts supported on commercial alumina ($Al_2O_3$) were prepared by an impregnation method, and were applied to the hydrogen production by auto-thermal reforming of ethanol. It was revealed that each catalyst retained its own metallic phase and product distribution strongly depended on the identity of active metal. Among the catalysts prepared, $Ni/Al_2O_3$ and $Co/Al_2O_3$ showed the best catalytic performance in the auto-thermal reforming of ethanol. However, the reaction mechanisms over these two catalysts were different. Ni/Al_2O_3 catalyst showed 100% ethanol conversion at $500^{\circ}C$, but it exhibited a rapid decrease in hydrogen selectivity. Although $Co/Al_2O_3$ catalyst showed an excellent performance in hydrogen selectivity, on the other hand, no significant improvement in hydrogen yield was observed due to the low ethanol conversion over the catalyst.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2726-2732
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• 2014

The promoting effect of rhodium on the structure and activity of the supported Cu-Co based catalysts for CO hydrogenation was investigated in detail. The samples were characterized by DRIFTS, $N_2$-adsorption, XRD, $H_2$-TPR, $H_2$-TPD and XPS. The results indicated that the introduction of rhodium to Cu-Co catalysts resulted in modification of metal dispersion, reducibility and crystal structure. DRIFTS results of CO hydrogenation at reaction condition (P=2 MPa, $T=260^{\circ}C$) indicated the addition of 1 wt % rhodium improved hydrogenation ability of Cu-Co catalysts. The ethanol selectivity and CO conversion were both improved by 1 wt % Rh promoted Cu-Co based catalysts. The alcohol distribution over un-promoted and rhodium promoted Cu-Co based catalysts obeys A-S-F rule and higher chain growth probability was got on rhodium promoted catalyst.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1222-1228
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• 2020

The adsorption and ion exchange properties of tin phosphate were studied in an aqueous solution of KCl, varing the pH and metal ion concentration in the solution. The data were explained on the basis of chemical equilibrium. Tin phosphate behaved as an acidic ion exchanger and had an adsorption selectivity toward the bivalent transition metal ions in the following order : Cu⁺² > Co⁺² > Ni⁺². As in the case of a weekly acidic exchanger, the change in hydration of metal ions played the dominant role in determining the selectivity of tin phosphate. In all cases the extent of adsorption increased with an increase in temperature and concentration. The apperance of irregular kinks in the titration curves justified the presence of several exchangeable adsorption sites with different pKa values.

• Economic and Environmental Geology
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• v.33 no.1
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• pp.31-40
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• 2000

Sorption characteristics of Pb, Cu, Cd, and Zn onto Ca- and Na-bentonites were investigated by the batch experiments in the condition of various pHs and concentrations of groundwater major anions (${So_4}^{2-}$ and ($HCO_3$), which can form a complex with heavy metals. The sorption removal of heavy metals steadily increases as pH increases. The sorption capability about heavy metals of both Ca-bentonite and Na-bentonite is in the order of Pb>Cu>Zn>Cd. The effect of pH and selectivity of heavy metals of bentonites were explained by the change of surface charge of bentonite and the speciation of heavy metals. Na-bentonite has a little higher sorption ability about heavy metals than that of Ca-bentonite. A high sorption removal of Pb in 0.1M sulfate solution may be attributed to the precipitation of $PbSo_4$(anglesite). However, sulfate has a slight effect on the sorption of CU, Cd and Zn. More than 99% of heavy metals were removed from the 0.1 M bicarbonate solution. However, the efficiency of sorption removal of heavy metals highly decreases in the bicarbonate solution of $10^{-2}$M to $10^{-4}$M. The speciation and saturation index calculated by the WATEQ4F program indicate that the sorption of anionic complexes such as ${Pb(CO_3)_2}^{2-}$, ${Cd(CO_3)_2}^{2-}$, ${Zn(CO_3)_2}^{2-}$, ${Cu(CO_3)_2}^{2-}$ and the precipitation of the solid phases such as $PbCO_3$(cerrusite), $ZnCO_3$(smithsonite), $CdCO_3$(obtavite) are involved in sorption removal of heavy metals in bicarbonate solution. The sorption capability about heavy metals of bentonites in the presence of anions shows the following order: Pb>Cu Cd>Zn.

• Journal of Environmental Science International
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• v.8 no.3
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• pp.387-391
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• 1999

$Pb^{2+}$ and $Cr^{3+}$ uptake capacity by Sargassum horneri was 185.5 mg $Pb^{2+}$/g biomass and 102.6 mg $Cr^{3+}$/g biomass, respectively. An adsorption equilibria were reached within about 0.5 hr for $Pb^{2+}$ and 1 hr for $Cr^{3+}$. The adsorption parameters for $Pb^{2+}$ and $Cr^{3+}$ were determined according to Langmuir and Freundlich model. With an increase in pH values of 2 to 5, $Pb^{2+}$ uptake was increased, however $Cr^{3+}$ uptake jwas constant. The selectivity of mixture solution showed the uptake order of $Pb^{2+}$>$Cu^{2+}$>$Cr^{3+}$>$Cd^{2+}$. $Pb^{2+}$ and $Cr^{3+}$ adsorbed by S. horneri could be recovered from 0.1M HCl, 0.1M ${HNO}_3$ and 0.1M EDTA by desorption process, and the efficiency of $Pb^{2+}$ desorption was above 98%, whereas the efficiency of $Cr^{3+}$ desorption was below 34%.

• Clean Technology
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• v.22 no.3
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• pp.196-202
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• 2016

In this study, ceria- based catalysts were prepared for dimethyl carbonate (DMC) synthesis and reaction conditions were evaluated for finding the optimal reaction route. In order to find optimal catalysts for DMC synthesis, calcination temperature and Cu(II) impregnation amount were evaluated. The oxidative carbonylation using methanol, carbon monoxide and oxygen and the direct synthesis using methanol and carbon dioxide were introduced for producing DMC. Following the law of Le Chatelier, the dehydration reaction was applied for enhancing the reactivity (methanol conversion) as removing water during the reaction. 2-cyanopyridine, as a chemical dehydration agent, was used. In the case of the oxidative carbonylation, methanol conversion rate increased from 15.1% to 38.7% and the DMC selectivity increased from 0% to 98.8%. In the case of the direct synthesis, methanol conversion rate increased from 1.0% to 77.8% and the DMC selectivity increased from 41.2% to 100.0%.