• Proceedings of the Korea Air Pollution Research Association Conference
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• 2010.04a
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• pp.526-527
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• 2010

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3659-3664
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• 2013

Eight representative explosives (ammonium perchlorate (AP), ammonium nitrate (AN), trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), cyclonite (RDX), cyclotetramethylenetetranitramine (HMX), pentaerythritol tetranitrate (PETN), and hexanitrostilbene (HNS)) were comprehensively analyzed with an ion trap mass spectrometer in negative ion mode using direct infusion electrospray ionization. MS/MS experiments were performed to generate fragment ions from the major parent ion of each explosive. Explosives in salt forms such as AP or AN provided cluster parent ions with their own anions. Explosives with an aromatic ring were observed as either $[M-H]^-$ for TNT and DNT or $[M]^{{\cdot}-}$ for HNS, while explosives without an aromatic ring such as RDX, HMX, and PETN were detected as an adduct ion with a formate anion, i.e., $[M+HCOO]^-$. These findings provide a guideline for the rapid and accurate detection of explosives once portable MS instruments become more readily available.

• Korean Journal of Materials Research
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• v.30 no.10
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• pp.533-541
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• 2020

UO₂ kernels, a key component of fuel elements for high temperature gas cooled reactors, have usually been prepared by sol-gel methods. Sol-gel processes have a number of advantages, such as simple processes and facilities, and higher sphericity and density. In this study, to produce 900 ㎛-sized UO₂ particles using an external gelation process, contact length extension of the NH₃ gas of the broth droplets pass and the improvement of the gelation device capable of spraying 14 M-NH₄OH solution are used to form 3,000 ㎛-sized liquid droplets. To produce high-sphericity and high-density UO₂ particles, HMTA, which promotes the gelation reaction in the uranium broth solution, is added to diffuse ammonium ions from the outside of the gelation solution during the aging process and generate ammonium ions from the inside of the ADU gel particles. Sufficient gelation inside of ADU gel particles is achieved, and the density of the UO₂ spheres that undergo the subsequent treatment is 10.78 g/㎤; the sphericity is analyzed and found to be 0.948, indicating good experimental results.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1119-1124
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• 2000

$\beta-Cyclodextrin$ derivatives connected with diaza-18-crown-6 through flexible bridges (R) at the secondary face 1a-c (1a: R = $-(CH_2)4-;$ 1b: R = $-CH_2CH_2OCH_2CH2-;$ 1c: R = $-(CH_2)8-)$ have been prepared. The associa tion constants of 1 with (2-naphthoxy)alkylammonium ions (2a: alkyl = butyl; 2b: alkyl = octyl) were determined by induced circular dichroism (ICD) spectroscopy and it was found that the derivatization of $\beta-CD$ with the diazacrown resulted in enhanced binding with 2, compared to the native $\beta-CD.$ ICD Characteristics of the host-guest complexes indicate that a part of the alkylammonium moiety of 2 is protruded from the secondary side of the $\beta-CD$ cavity, and the guest molecules 2a and 2b move to the secondary and primary side, respectively, to make the binding of the ammonium group with the diaza-18-crown-6 moiety more feasible. The energy accompanied by the relocation of the guest molecules inside $\beta-CD$ moiety is compensated by the interaction energy between the ammonium ion and diazacrown ether.

• Korean Journal of Materials Research
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• v.31 no.9
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• pp.481-487
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• 2021

ZnO particles are successfully synthesized at 150 ℃ for 30 min using zinc acetate as the Zn source and 1,4-butanediol as solvent using a relatively facile and convenient glycol process. The effect of ammonium hydroxide amounts on the growth behavior and the morphological evolution of ZnO particles are investigated. The prepared ZnO nanoparticle with hexagonal structure exhibits a quasi-spherical shape with an average crystallite size of approximately 30 nm. It is also demonstrated that the morphology of ZnO particles can be controlled by 1,4-butanediol with an additive of ammonium hydroxide. The morphologies of ZnO particles are changed sequentially from a quasi-spherical shape to a rod-like shape and a hexagonal rod shape with a truncated pyramidal tip, exhibiting preferential growth along the [001] direction with increasing ammonium hydroxide amounts. It is demonstrated that much higher OH^- amounts can produce a nano-tip shape grown along the [001] direction at the corners and center of the (001) top polar plane, and a flat hexagonal symmetry shape of the bottom polar plane on ZnO hexagonal prisms. The results indicate that the presence of NH⁴⁺ and OH^- ions in the solution greatly affects the growth behaviors of ZnO particles. A sharp near-band-edge (NBE) emission peak centered at 383 nm in the UV region and a weak broad peak in the visible region between 450 nm and 700 nm are shown in the PL spectra of the ZnO synthesized using the glycol process, regardless of adding ammonium hydroxide. Although the broad peak of the deep-level-emission (DLE) increases with the addition of ammonium hydroxide, it is suggested that the prominent NBE emission peaks indicate that ZnO nanoparticles with good crystallization are obtained under these conditions.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.543-550
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• 2009

The single-crystal structure of largely ammonium-exchanged zeolite Y dehydrated at room temperature (293 K) and 1 ${\times}\;10^{-6}$ Torr. has been determined using synchrotron X-radiation in the cubic space group $Fd\overline{3}m\;(a=24.9639(2)\AA)$ at 294 K. The structure was refined to the final error index $R_1$ = 0.0429 with 926 reflections where $F_o>4\sigma(F_o)$; the composition (best integers) was identified as |$(NH_4)_{60}Na_{11}$|[$Si_{121}Al_{71}O_{384}$]-FAU. The 11 $Na^{+}$ ions per unit cell were found at three different crystallographic sites and 60 ${NH_4}^{+}$ ions were distributed over three sites. The 3 $Na^{+}$ ions were located at site I, the center of the hexagonal prism ($Na-O\;=\;2.842(5)\;\AA\;and\;O-Na-O\;=\;85.98(12)^{\circ}$). The 4 $Na^{+}$ and 22 ${NH_4}^{+}$ ions were found at site I' in the sodalite cavity opposite the double 6-rings, respectively ($Na-O\;=\;2.53(13)\;\AA,\;O-Na-O\;=\;99.9(7)^{\circ},\;N-O\;=\;2.762(11)\;\AA,\;and\;O-N-O =\;89.1(5)^{\circ}$). About 4 $Na^{+}$ ions occupied site II ($(Na-O\;=\;2.40(4)\;\AA\;and\;O-Na-O\;=\;108.9(3)^{\circ}$) and 29 ${NH_4}^{+}$ ions occupy site II ($N-O\;=\;2.824(9)\;\AA\;and\;O-N-O\;=\;87.3(3)^{\circ}$) opposite to the single 6-rings in the supercage. The remaining 9 ${NH_4}^{+}$ ions were distributed over site III' ($N-O\;=\;2.55(3),\;2.725(13)\;\AA\;and\;O-N-O\;=\;94.1(13),\;62.16(15),\;155.7(14)^{\circ}$).

• Journal of Korean Society of Environmental Engineers
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• v.32 no.7
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• pp.730-737
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• 2010

It is very important to remove fluoride ion before treating semiconductor wastewater containing high concentration of ammonia, phosphates, and fluoride ions by struvite formation. Calcium ion was generally added for the removal of fluoride ion. However, calcium ions remained after removal of fluoride ion can deteriorate the performance of struvite crystalization. It should be removed completely before struvite formation. In this study, the effect of fluoride and calcium ion concentration on the struvite crystalization was investigated. Removal efficiencies of ortho-phosphate with struvite formation were more abruptly decreased than those of ammonium nitrogen, as increase of fluoride ion concentration in synthetic wastewater. The structures of struvite formed in synthetic wastewater containing calcium ion of up to 500 mg/L were identical. Purity of struvite was deteriorated as increase of calcium ion over 500 mg/L. Removal efficiencies of ammonium nitrogen were more decreased than those of phosphate ions as increase of cacium ion in synthetic wastewater.

• Korean Journal of Microbiology
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• v.21 no.3
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• pp.135-142
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• 1983

The presence of polyphosphate phosphohydrolase (PPPH) and tripolyphosphate phosphohydrolase (TPPH) in Chlorella ellipsoidea were confirmed from the cell-free extract of the algal cells and three forms of PPPH were isolated, purified, and measured Km-Vmax value and inhibitory effect by metal ions, respectively. PPPH was most active at pH7.2, whereas TPPH at pH 7.6. Both enzymes exhibited their maximum activity at $37^{\circ}C$. For the manifestation of catalytic activity, divalent, divalent metal ions are needed, and the best activator for both enzymes was $Co^{++}\;ions\;(10^{-3}M)$. These enzymes were inhibited by $Hg^{++}\;ions\;(10^{-3}M)$ considerably. PPPH from Chlorella ellipsoidea was purified by ammonium sulfate fractionation, ion-exchange chromatography on DEAE-Sephadex A-25, and gel filtration on Sephadex G-100, and some properties of the three different fraction with PPPH activity $(PPPH_1,\;PPPH_2,\;and\;PPPH_3)$ were found, i.e, PPPH has multiple form. The Km values of $PPPH_1,\;PPPH_2,\;and\;PPPH_3$ obstained were $6.25{\times}10^{-4}M,\;10^{-4}M-4/M,\;and\;3.33{times}10^{-4}M$ and Vmax were 3.33 mM/min, 3.33 mM/min, and 2.67 mM/min, respectively. It was shown that the types of inhibition of $Hg^{++} on the activities of three forms of PPPH were competitive inhibition.

• Journal of Environmental Science International
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• v.25 no.5
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• pp.727-736
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• 2016

The ambient mass concentration and chemical composition of the $PM_{2.5}$ were determined at the highland site with 1,100 m above sea level on Jeju Island from June 2013 to November 2014. Yearly averaged mass concentration of $PM_{2.5}$ was $11.97{\pm}8.63{\mu}g/m^3$. $PM_{2.5}$ concentrations were highest during the spring, while they tended to be lowest during the summer. Eight water soluble ionic species attributed 45.5% to $PM_{2.5}$ mass. $SO{_4}^{2-}$, $NO_3{^-}$ and $NH_4{^+}$ were major ions, which occupied to 27.9%, 3.7% and 12.3%, respectively. The greatest contributors to total mass concentration of water-soluble ions contained in $PM_{2.5}$ were sulfate, ammonium and nitrate. These three ions accounted for 96.6% in total ions mass concentration of $PM_{2.5}$. We could infer that these three secondary ions exist mostly in the form of $(NH_4)_2SO_4$ and $NH_4NO_3$. $Ca^{2+}$ and $Mg^{2+}$ had a good relationship and with r=0.9. The molar ratio of $Mg^{2+}/Ca^{2+}$ in this study was lower than the value observed in sea water and higher than that in soil dust, indicating that these two ions originated from other sources rather than ocean and soil dust in this study.

• Journal of the Korean Applied Science and Technology
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• v.25 no.1
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• pp.65-72
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• 2008

The ion exchangers supported on silica gel containing primary, secondary, or tertiary amine groups show a behaviour that is weakly acidic, while the quaternary salts are strongly acidic. These properties change according to the hydrophilicities of the modifier functional groups. Ammonium salt derivatives supported on silica gel were prepared from silica modified with 3-Aminopropyltriethoxysiliane and N-3-(Trimethoxysilyl)propylehtylene diamine. The preparation and the ion exchange properties of two systems were discussed. Two systems have different hydrophilicities and contain ammonium chloride derivatives of 3-amminopropyltriethoxysilane and N-3-(triehtoxysilyl)propyl ethylene diamine supported on silica gel, $SA^+/Cl^-$ and $SA^+/Cl^-$, respectively. The high affinity to perchlorate ion presented by the $SA^+/Cl^-$ through the equilibrium studies of ion exchange led us to its application as an ion selective electrode for the perchlorate ion. The determination of the perchlorate ion in the presence of other anions and in complexes is very difficult. Few analytical methods are available and most of them are indirect. Both materials showed potential use as an ion exchanger; they are thermically stable, achieve equilibrium rapidly in the presence of suitable exchanger ions, and are easily recovered.