• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.362-367
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• 1991

Rates of nucleophilic substitution reaction ([Pd (ONN) Cl] + Y$^-\;{\rightleftharpoons}$ [Pd (ONN)Y] + Cl$^-$ ; Y = SCN$^-$, CN$^-$, N$_3^-$, imidazole, pyridine) have been measured in methanol by spectrophotometric method at various temperatures. A set of nucleophilic reactivity constants, n$_{Pd}^{\circ}$ has been calculated. These values show an order of nucleophilicity CN$^-$ > SCN$^-$ > N$_3^-$ > Imidazole > Pyridine. The enthalpy of activation are small positive values and the entropy of activation are large negative values. From these results, it can be inferred that the nucleophilic substitution reaction proceeds through an associative (A) mechanism.

• Analytical Science and Technology
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• v.11 no.2
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• pp.92-95
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• 1998

K-SGICs(synthetic graphite intercalation compounds) were synthesized in a modified two-bulb pyrex tube. The pressure in the two-bulb tube was maintained at approximately $10^{-3}$ torr for the reaction of potassium and graphite. Deintercalation process of the K-SGlCs obtained by the modified method was heat-treated by keeping in liquid paraffin between $25^{\circ}C$ and $1400^{\circ}C$. The thermal stability and the temperature dependence of the K-SGICs were characterized using differential scanning calorimeter(DSC) analyzer. Enthalpy and entropy for K-SGIC formations were calculated by confirming the deintercalation and thermodynamic exothermic reactions depending on the various temperatures. The structure changes and thermal stability of K-SGICs during the deintercalation reaction of potassium ions and the interlayer spaces of the synthetic graphite were identified by X-ray diffraction(XRD).

• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.514-519
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• 2017

Adsorption characteristics of acid green 27 dye using activated carbon were investigated as function of adsorbent dose, pH, initial concentration, contact time and temperature. Freundlich isotherm explained adsorption of acid green 27 dye very well and Freundlich separation factors (1/n=0.293~0.387) were found that this process could be employed as effective treatment method. Kinetic studies showed that the kinetic data were well described by the pseudo second-order kinetic model. Pseudo second rate constant ($k_2$) decreased with the increase in initial acid green 27 concentration. Activation energy (10.457 kJ/mol) and enthalpy (79.946 kJ/mol) indicated that adsorption process was physisorption and endothermic. Since Gibbs free energy decreased with increasing temperature, spontaneity of adsorption reaction increased with increasing temperature in the temperature range of 298 K~318 K.

• Journal of the Korean Chemical Society
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• v.33 no.6
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• pp.607-613
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• 1989

The chemical equilibria of Ni(II)-tetraamine (tetraamine = 2,12-dimethyl-3,7,11,17-tetraazabicyclo-11,3,1-heptadeca-1(17),2,11,13,15-pentaene) complex ion in water, acetonitrile, acetone and nitromethane were investigated using spectrophotometric method, respectively. The equilibria between low-spin ($D_{4h}$) and high-spin ($O_h$) structures of Ni-tetraamine complex ion were presented in water, acetonitrile and acetone, but not in nitromethane. The eqilibrium constants, the reaction enthalpies and the reaction entropies were determined from analysis of the temperature dependence of the electronic spectra. The formation of the triplet species ($O_h$) was found to be exothermic. The solvent and electrolyte effects on the equilibrium constants could be explained by the dielectric constants of solvents and the reaction entropies.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.309-314
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• 2015

Adsorption of brilliant blue FCF dye from aqueous solution using coconut shell based activated carbon was investigated. Batch experiments were carried out as function of adsorbent dose, initial concentration, contact time and temperature. The equilibrium adsorption data were analyzed by Langmuir and Freundlich model. The results indicate that Freundlich model provides the best correlation of the experimental data. Base on the estimated Freundlich constant (1/n=0.129~0.212), this process could be employed as effective treatment method. Adsorption kinetics experimental data were modeled using the pseudo-first-order and pseudo-second-order kinetic equation. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. Base on the negative Gibbs free energy value (-4.81~-10.33 kJ/mol) and positive enthalpy value (+78.59 kJ/mol) indicate that the adsorption is spontaneous and endothermic process.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.255-261
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• 2016

Adsorption experiments of Acid Yellow 14 dye using activated carbon were carried out as function of adsorbent dose, pH, initial concentration, contact time and temperature. The equilibrium adsorption data were analyzed by Langmuir, Freundlich and Temkin isotherm model. The experimental data were best represented by Freundlich isotherm model. Base on the estimated Freundlich constant (1/n=0.129~0.212) and Langmuir separation factor ($R_L=0.202{\sim}0.243$), this process could be employed as effective treatment method. The heat of adsorption of Temkin isotherm model was 5.101~9.164 J/mol indicated that the adsorption process followed a physical adsorption. Adsorption kinetics experimental data were modeled using the pseudo-first-order and pseudo-second-order kinetic equation. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. Base on the negative Gibbs free energy (-4.81~-10.33 kJ/mol) and positive enthalpy (+78.59 kJ/mol) indicate that the adsorption is spontaneous and endothermic process.

• Composites Research
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• v.21 no.1
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• pp.16-21
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• 2008

The cure behavior of epoxy resin with a conventional amide-type hardener(HD) was investigated in the presence of castor oil(CO), cashew nut shell liquid(CNSL) and CNSL-formaldehyde resin(CFR) by using a dynamic differential scanning calorimetry(DSC). The activation energy of curing reaction was also calculated based on the non-isothermal DSC thermograms at various heating rates. An one-stage curing was noted in the case of epoxy resin filled with CO, while the epoxy resin with CNSL and CFR showed a two-stage curing process. A competitive cure reaction was noted for the epoxy resin/CNSL(or CFR)/HD blends. In the absence of HD, the CFR showed lower values of curing enthalpy than that of CNSL. The activation energy of epoxy resin curing increased with increasing the CNSL and CFR loading.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.279-284
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• 2023

Isothermal titration calorimetry (ITC) is a useful technique to obtain thermodynamic binding properties such as enthalpy, Gibbs free energy, entropy, and stoichiometry of the chelation reaction. A single independent binding site model was used to evaluate the thermodynamic binding properties in BaCl₂ and ethylenediaminetetraacetic acid (EDTA) in Trince and HEPES buffers. ITC enables us to elucidate the binding mechanism and find an optimal chelation condition for BaCl₂ and EDTA in the pH range of 7~11. Chelation of BaCl₂ and EDTA is a spontaneous endothermic reaction. As pH increased, entropic contributions dominated. The optimal pH range is narrow around pH 9.0, where 1:1 binding between BaCl₂ and EDTA occurs.

• Journal of the Korean Chemical Society
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• v.32 no.6
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• pp.593-602
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• 1988

Polymer-supported crown ethers (Ps-CE) which can be used for phase-transfer catalyst (PTC) were synthesized for the purpose of allowing reusable function to ordinary crown ethers, and the kinetics of the liquid-solid-liquid triphase-catalyzed nucleophilic displacement reaction of iodide (aqueous phase) on 1-bromooctane (organic phase) using synthesized Ps-CE (solid) were studied. Ps-CE were obtained by grafting of hydroxymethyl crown ethers to 1~2% cross-linked chloromethylated polystyrene. All reactions followed a pseudo-first order dependency on the 1-bromooctane concentration and the observed rate constants $(k_{obsd})$ were linearly related to the molar equivalents of Ps-CE, and were subjected to the influence of cross-linking density of polymer backbone, solvent and the reaction temperature. The catalytic activity of Ps-CE was also compared with that of structurally similar soluble crown ethers, and used Ps-CE were easily recovered after the reaction by simple filtration and could be reused without loss of catalytic activity in the same anionic displacement reaction. Enthalpies and entropies of activation associated with the displacement were 10~20kcal $mol^{-1}, 20~55eu. respectively, and the free energy of activation was ~30kcal mol^{-1}$.

• Clean Technology
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• v.20 no.1
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• pp.35-41
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• 2014

Batch adsorption studies were carried out for equilibrium, kinetic and thermodynamic parameters for quinoline yellow adsorption by granular activated carbon ($8{\times}30mesh$, $1,578m^2/g$) with varying the operating variables like initial concentration, contact time and temperature. Equilibrium adsorption data were fitted into Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms. From estimated Langmuir constant ($R_L=0.0730{\sim}0.0854$), Freundlich constant (1/n = 0.2077~0.2268), this process could be employed as effective treatment for removal of quinoline yellow. From calculated Temkin constant (B = 15.759~21.014 J/mol) and Dubinin-Radushkevich constant (E = 1.0508~1.1514 kJ/mol), this adsorption process is physical adsorption. From kinetic experiments, the adsorption process were found to confirm to the pseudo second order model with $r^2$ > 0.99 for all concentrations and temperatures. Thermodynamic parameters like activation energy, change of free energy, enthalpy, and entropy were also calculated to predict the nature adsorption. The activation energy value (+35.137 kJ/mol) and enthalpy change (35.03 kJ/mol) indicated endothermic nature of the adsorption process. Entropy change (+134.38 J/mol K) showed that increasing disorder in process. Free energy change found that the spontaneity of process increased with increasing adsorption temperature.