• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.24-27
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• 1992

Silver sols are aggregated by a Cu or Zn rod. This is maybe due to the reduction of $Ag^+$ ion on the surfaces of silver sols to Ag metal by oxidation-reduction reaction with Cu or Zn metal. Raman spectra of silver sols aggregated by a Cu rod have been studied. The evidence of borate and nitrate ions adsorbed on silver colloid surfaces is found. It is also found that these ions adsorbed on silver colloid surfaces are easily replaced by adsorbated added.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.125-131
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• 2009

Reductive dechlorination of polychlorinated dibenzo-p-dioxins (PCDDs) and its toxicity change were predicted by the linear free energy relationship (LFER) model to assess the zero-valent iron (ZVI) and anaerobic dechlorinating bacteria (ADB) as electron donors in PCDDs dechlorination. Reductive dechlorination of PCDDs involves 256 reactions linking 76 congeners with highly variable toxicities, so is challenging to assess the overall effect of this process on the environmental impact of PCDD contamination. The Gibbs free energies of PCDDs in aqueous solution were updated to density functional theory (DFT) calculation level from thermodynamic results of literatures. All of dechlorination kinetics of PCDDs was evaluated from the linear correlation between the experimental dechlorination kinetics of PCDDs and the calculated thermodynamics of PCDDs. As a result, it was predicted that over 100 years would be taken for the complete dechlorination of octachlorinated dibenzo-p-dioxin (OCDD) to non-chlorinated compound (dibenzo-p-dioxin, DD), and the toxic equivalent quantity (TEQ) of PCDDs could increase to 10 times larger from initial TEQ with the dechlorination process. The results imply that the single reductive dechlorination using ZVI or ADB is not suitable for the treatment strategy of PCDDs contaminated soil, sediment and fly ash. This LFER approach is applicable for the prediction of dechlorination process for organohalogen compounds and for the assessment of electron donating system for treatment strategies.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.3
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• pp.323-330
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• 2008

The study presents the results of 1,4-dioxane degradation using zero valent (Fe$^0$) or Fe$^{2+}$ ions with and without UV. During the reaction, the change of [Fe$^{2+}$] and [Fe$^{2+}$]/[Fe(t)], the concentration ratio of ferrous ion to total iron ion in solution was measured. Less than 10% degradation of 1,4-dioxane was observed by UV-only, Fe$^0$-only, and Fe$^{2+}$-only conditions, and also the changes of [Fe$^{2+}$] and [Fe$^{2+}$]/[Fe(t)] were minimal in each reaction. However, the oxidation of Fe$^0$ was enhanced with the irradiation of UV by approximately 25% and the improvement of 1,4-dioxane degradation was observed. Fenton reaction ($Fe^{2+}+H_2O_2$) showed higher degradation efficiency of 1,4-dioxane until 90 min, which of the degradation was stopped after that time. In the reaction of Fe$^{2+}$ and UV, the ratio of [Fe$^{2+}$]/[Fe(t)] decreased then slowly increased after a certain time indicating the reduction of Fe3+ to Fe$^{2+}$. In case of Fe$^0$ in the presence of UV, the first-order rate constant was found to be 1.84$\times$10$^{-3}$ min$^{-1}$ until 90 min, and then changed to 9.33$\times$10$^{-3}$ min$^{-1}$ when the oxidation of Fe$^{2+}$ mainly occurred. In this case [Fe$^{2+}$]/[Fe(t)] kept decreasing for the reaction. However, the addition of perchlortae (ClO$_4^-$) in the reaction of Fe$^0$ and UV induced the continuous increase of [Fe$^{2+}$]/[Fe(t)] ratio. The results mean the primary degradation factor of 1,4-dioxane is the oxidation by the radicals generated from the redox reaction between Fe$^{2+}$ and Fe$^{3+}$. Also, both UV and ClO$_4^-$ played the role inducing the reduction of Fe$^{3+}$, which is important to degrade 1,4-dioxane by enhancing the generation of radicals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5610-5614
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• 2012

Performance of catalyst was studied with various operating conditions for selective catalytic reduction of $NO_x$ with $NH_3$. It is confirmed that catalysts containing Mn and Cu have a good efficiency in the usage of oxygen by the $H_2$-TPR analysis. In the case of catalyst #1, $NO_x$ conversion was decrease with the increase of reaction temperature. But in the case of catalyst #2, $NO_x$ conversion was increased and then remained constant with the increase of reaction temperature. This phenomenon is due to the difference of the $NH_3$ oxidation of both catalysts.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.45-49
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• 2016

In the presence of poly(4-styrene sulfonate) (PSS) and excess amount of graphene oxide (GO), we conducted in-situ polymerization of 3,4-ethylenedioxythiophene (EDOT) without an oxidant. XPS and IR spectroscopies of the product (GO-P) showed that PEDOT/PSS was successfully synthesized by oxidative polymerization of EDOT and hybridized with GO. GO-P displayed a stable aqueous suspension, however, the high content (42%) of GO in GO-P diminished electrical conductivity down to $15S{\cdot}m^{-1}$. Annealing of GO-P films at $200^{\circ}C$ for 8 hr induced partial reduction of GO and finally enhanced electrical conductivity up to $212S{\cdot}m^{-1}$.

• Journal of the Korean Institute of Gas
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• v.4 no.1 s.9
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• pp.40-48
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• 2000

A fuel cell is an electrochemical device continuously converting the chemical energy in a fuel and an oxidant to electrical energy by going through an essentially invariant electrode-electrolyte system. Phosphoric acid fuel cell employs concentrated phosphoric acid as an electrolyte. The cell stack in the fuel cell, which is the most important part of the fuel cell system, is made up of anode where oxidation of the fuel occurs cathode where reduction of the oxidant occurs; and electrolyte, to separate the anode and cathode and to conduct the ions between them. Fuel cell performance is associated with many parameters such as operating and design parameters associated with the system configuration. In order to understand the design concepts of the phosphoric fuel cell and predict it's performance, we have here introduced the simulation of the fuel-cell stack which is core component and modeled in a 3-dimensional grid space. The concentration of reactants and products, and the temperature distributions according to the flow rates of an oxidant are computed by the help of a computational fluid dynamic code, i.e., FLUENT.

• Journal of the Korean Chemical Society
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• v.56 no.6
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• pp.731-738
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• 2012

The purpose of this study is to analyze the understandings of science high school students on the conception of chemical cell in relation to chemical equilibrium from the microscopic viewpoint at molecular level through questionnaires and follow-up interviews. The results show that they have high understandings on the chemical equilibrium states in the electrochemical cell and on the redox reaction taking place simultaneously when a metal electrode is immersed in the metal ion solution. However, they do not fully comprehend the development of electrical potential difference, electron movement, electrode potential measurement in the half-cells, and calculation of the net cell voltage between anode and cathode in the chemical cell because of difficulties in the microscopic understanding the interaction on the interface at the electrode and the electrolyte solution.

• Journal of the Korean Applied Science and Technology
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• v.34 no.3
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• pp.487-494
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• 2017

Since nitrate nitrogen is quite stable in aqueous solution, considerable skill is required to remove it. Low concentrations of nitrate nitrogen are easily removed, while high concentrations of nitrate nitrogen are difficult to remove. This study is to show that nitrate nitrogen in the form of gaseous nitrogen can be removed by using zinc ball with a diameter of about 3mm and to test the removal characteristics of nitrate nitrogen under various reaction conditions. As a result of this study, the treatment efficiency of nitrate nitrogen by continuous treatment with zinc ball was about 80%. However, there is a problem that the wastewater must be maintained in an acidic atmosphere of about pH 2, and the treated wastewater must be neutralized and discharged.

• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.624-628
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• 2008

Nitrous oxide ($N_2O$), known as one of the major greenhouse gases, is an important component of the earth's atmosphere, and gives rise to precursor of acid rain and photochemical smog. For the removal of $N_2O$ and other nitrogen oxides, the SCR reaction system with various reductants is widely used. This study is based on the results of experimental and theoretical examinations on the catalytic decomposition of sole nitrous oxide ($N_2O$) and selective catalytic reduction of $N_2O$ with $CH_4$ in the presence of oxygen using mixed metal oxide catalysts obtained from hydrolatcite-type precursors. When $CH_4$ is fed together with a reductant, it affects positively on the $N_2O$ decomposition activity. At an optimum ratio of $CH_4$ to $O_2$ mole ratio, the $N_2O$ conversion activity is enhanced on the SCR reaction with partial oxidation of methane.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.512-518
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• 2008

The present work studied the selective catalytic reduction (SCR) of NO to $N_2$ by $NH_3$ over $V/TiO_2$ focusing on NOx control for the stationary sources. The SCR process depends mainly on the catalyst performance. The reaction characteristics of SCR with $V/TiO_2$ catalysts were closely examined at low and high temperature. In addition, adsorption and desorption characteristics of the reactants on the catalyst surface were investigated with ammonia. Seven different $TiO_2$ supports containing the same loading of vanadia were packed in a fixed bed reactor respectively. The interaction between $TiO_2$ and vanadia would form various non-stoichiometric vanadium oxides, and showed different reaction activities. There were optimum calcination temperatures for each samples, indicating different reactivity. It was finally found from the $NH_3-TPD$ test that the SCR activity was nothing to do with $NH_3$ adsorption amount.