• Clean Technology
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• v.27 no.3
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• pp.261-268
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• 2021

Equilibrium, kinetics, and thermodynamics of adsorption of acid black 1 (AB1) by coal-based granular activated carbon (CGAC) were investigated with the adsorption variables of initial concentration of dye, contact time, temperature, and pH. The adsorption reaction of AB1 by activated carbon was caused by electrostatic attraction between the surface (H⁺) of activated carbon and the sulfite ions (SO₃^-) and nitrite ions (NO₂^-) possessed by AB1, and the degree of reaction was highest at pH 3 (97.7%). The isothermal data of AB1 were best fitted with Freundlich isotherm model. From the calculated separation factor (1/n) of Freundlich, it was confirmed that adsorption of AB1 by activated carbon could be very effective. The heat of adsorption in the Temkin model suggested a physical adsorption process (< 20 J mol^-1). The kinetic experiment favored the pseudo second order model, and the equilibrium adsorption amount estimated from the model agreed to that given by the experiments (error < 9.73% ). Intraparticle diffusion was a rate controlling step in this adsorption process. From the activation energy and enthalpy change, it was confirmed that the adsorption reaction is an endothermic reaction proceeding with physical adsorption. The entropy change was positive because of an active reaction at the solid-liquid interface during adsorption of AB1 on the activated carbon surface. The free energy change indicated that the spontaneity of the adsorption reaction increased as the temperature increased.

• Journal of the Korean Ceramic Society
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• v.23 no.1
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• pp.33-43
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• 1986

The synthesis of high-purity AlN by a vapor-phase reaction was investigated using the $NH_3-AlCl_3-H_2$ reacting system. The theoretical yields of AlN were determined from th thermodynamic equilibrium composi-tions. It was shown that the yields above 90% could by obtained even in the range of relatively low temper-ature of 600-1200K. The reaction temperature and the initial amounts/ratios of the reacting gases showed significant effects on the yields but the total pressure did not. The experimental results showed that a high-purity AlN having a needle shape was the only product as a solid phase and its amount produced increased with the reaction temperature. While the degree of agglmera-tion of the synthesized AlN increased with the reaction temperature the size of each particle consisting of the agglomerates was independent of the temperature but grew from 0.09 to 0.115${\mu}{\textrm}{m}$ with the flow rate of NH3. These experimental results were compared with the theoretical aspects for the synthesis of a high-purity AlN.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.222-227
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• 2007

The adsorption features of fluoride ion on the oyster shell have been investigated for the purpose of the employment of waste oyster shell as an adsorbent for the treatment of fluoride ion-containing wastewater. The major component of oyster shell was examined to be Ca with minor components of Na, Si, Mg, Al, and Fe. As the initial concentration of fluoride ion was raised, its absorbed amount was enhanced at equilibrium, however, the adsorption ratio of fluoride ion compared with its initial concentration was shown to be decreased. Also, adsorption of fluoride ion onto the oyster shell resulted in the formation of $CaF_2$ in the morphological structure of adsorbent. Kinetic analysis showed that the adsorption reaction of fluoride ion generally followed a second order reaction with decreasing rate constant with the initial concentration of adsorbate. Freundlich model agreed well with the adsorption behavior of fluoride ion at equilibrium and the adsorption reaction of fluoride ion was examined to be endothermic. Several thermodynamic parameters for the adsorption reaction were calculated based on thermodynamic equations and the activation energy for the adsorption of fluoride ion onto oyster shell was estimated to be ca. 13.589 kJ/mole.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.50-57
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• 1989

A pressure effect of the dehydrogenation of ethylalcohol catalyzed by alcoholdehydrogenase was observed in Tris-HCl buffer, pH 8.8 from $25^{\circ}C$ to $35^{\circ}C$ under high pressure system by using our new theory. The theory makes it possible for us to obtain all rate and equilibrium constants for each step of all enzymatic reaction with a single intermediate. We had enthalpy and volume profiles of the dehydrogenation to suggest a detail and reasonable mechanism of the reaction. In these profiles, both enthalpy and entropy of the reaction are positive and their values decrease with enhancing pressure. It means that the first step is endothermic reaction, and its strength decrease with elevating pressure. At the same time, all activation entropies have large negative values, which prove that not only a ternary complex has a more ordered structure at transition state, but also water molecules make a iceberg close by the activated complex. In addition to this fact, the first and second step equilibrium states are controlled by enthalpy. The first step kinetic state is controlled by enthalpy but the second step kinetic state is controlled by entropy.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.144-148
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• 2006

Characteristics of a plasma reactor for partial oxidation of methane, especially focused on the role and effectiveness of plasma chemistry, is investigated. Partial oxidation of methane is investigated using a rotating arc which is a three dimensional version of a typical glidingarc. The rotating arc has both the characteristics of equilibrium and non-equilibrium plasma. Non-equilibrium characteristics of the rotating gliding arc can be increased by rotating an elongated arc string attached at both the tip of inner electrode and the edge of outer electrode. In this way, plasma chemistry can be enhanced and hydrogen selectivity can reach almost 100% that is much higher than thermal equilibrium condition. As a result, the present study enables the strategic approach of the plasma reforming process by means of appropriate reactor design to maximize plasma effect and resulting in maximized reaction efficiency.

• Polymer(Korea)
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• v.26 no.4
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• pp.422-430
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• 2002

The kinetics of polycondensation of bishydroxyethyl naphthalate has been studied in the range of 241 -$260^{\circ}C$ using antimony trioxide catalyst. The reaction was performed in a batch reactor and the concentration of reaction mixture was measured with HPLC. The activation energy values of forward and reverse reaction determined from molecular species model were found to be 19.7 and 31.4 kcal/mole, respectively, and the equilibrium constants were in the range of 1.4-2.0, which were larger than that of polycondensation of PET and varied to some degree with temperature. It was confirmed by applying the Flory's distribution function that the reaction rate of the hyroxyethyl group does not depend on the molecular size. By applying functional group model, we observed that there was few difference between the activation energy of the forward reaction and that of reverse reaction, therefore the equilibrium constant has almost constant value of 1.4. The rate constants obtained from functional group model was about 3-4 times larger than that from molecular species model, which showed that both model explains the reaction system well. Although the molecular species model should predict the concentration of as many as ten molecules, it fits for the experimental results well.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.1051-1054
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• 2008

The entropy production in a non-equilibrium state based on the reversible Oregonator model of the Belousov-Zhabotinskii (BZ) reaction system has been studied. The reaction affinity and the reaction rate for the individual steps have been calculated by varying the concentrations of key variables in the system. The result shows a linear relationship between the reaction affinity and the reaction rate in the given concentration range. However, the overall entropy calculated on the basic assumption that the entropy in a reaction system corresponds to the summation of a product of reaction affinity and reaction rate of individual steps shows a nonlinearity of the reaction system. The results well agrees with the fact that the entropy production is not linear or complicated function in a non-linear reaction system.

• Journal of the Korean Ceramic Society
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• v.45 no.2
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• pp.90-93
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• 2008

The oxygen gas behavior in PDP (plasma Display Panel) glass melts doped with sulfate ($SO_4^{-2}$) or blast furnace slag (BFS, $S^{2-}$) or both by means of yttria-stabilized zirconia (YSZ) electrodes was observed after the first fining. The temperature dependence of oxygen equilibrium pressure ($P_{O2}$) in each melt showed typical behavior, namely $P_{O2}$ decreased as temperature decreased. This suggests that an oxidation of $S^{4+}$ to $S^{6+}$ took place. However, the $P_{O2}$-value at constant temperature increased in the following order: BFS$P_{O2}$ of the melt doped with sulfate+BFS was much lower than that of the melt with only sulfate, although only 10% of sulfur was added by the BFS. This behavior can be explained by the redox reaction between sulfide ions in the BFS and dissolved oxygen ions in the melt during the first fining.

• Journal of the Korean Ceramic Society
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• v.44 no.8
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• pp.419-423
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• 2007

The behavior of oxygen gas participating in fining was observed in CRT (Cathode Ray Tube) glass melts doped with $Sb_2O_5\;or\;CeO_2$ by means of a yttria-stabilized zirconia (YSZ) electrode. The temperature dependence of the oxygen equilibrium pressure ($P_{o2}$) or the activity in both melts showed typical behavior corresponding to a theoretical redox reaction. In other words, the $P_{o2}$ value of melts with $CeO_2$ was lower than that of melts with $Sb_2O_5$ above $1250^{\circ}C$. The result implies that $Sb_2O_5$, is more efficient as a fining agent compared to $CeO_2$. On the other hand, melts from a batch containing $Sb_2O_5\;and\;KNO_3$ showed much higher $P_{o2}$ values compared to melts without $KNO_3$ above $1350^{\circ}C$. It is suggested that the addition of $KNO_3$ to CRT glass batch contributes partly to the first fining of the melts.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.218-221
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• 2008

A $Fe(OH)_2$ suspension was prepared by mixing iron sulfate and a weak alkali ammonia solution. Following this, iron oxides were synthesized by passing pure oxygen through the suspension (oxidation). The effects of different reaction temperatures ($30^{\circ}C$, $50^{\circ}C$, $70^{\circ}C$) and equivalent ratios ($0.1{\sim}10.0$) on the formation of iron oxides were investigated. An equilibrium phase diagram was established by quantitative phase analysis of the iron oxides using the Rietveld method. The equilibrium phase diagram showed a large difference from the equilibrium phase diagram of Kiyama when the equivalent ratio was above 1, and single $Fe_3O_4$ phase only formed above an equivalent ratio 2 at all reaction temperatures. Kiyama synthesized iron oxide using iron sulfate and a strong alkali NaOH solution.