• Bulletin of the Korean Chemical Society
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• v.3 no.2
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• pp.79-81
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• 1982

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3184-3190
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• 2012

Color impurity in industrial effluents pose a significant risk to human health and the environment, so much effort has been expended to degrade them using various methods, including the use of clay minerals as adsorbent. The purpose of this study was to advance understanding of the mechanisms for the removal of methylene blue (MB) from aqueous solutions onto montmorillonite as an adsorbent. Preliminary experiments showed that montmorillonite was effective for this purpose and adsorption equilibrium could be reached in about 24 h. Adsorption capacity of the clay decreased with increase in temperature and ionic strength, and increased with in pH. The fitness of equilibrium data to common isotherm equations such as the Langmuir, Freundlich, Elovich, Temkin and Dubinin-Radushkevich were tested. The Langmuir equation fitted to equilibrium data better than all tested isotherm models. Thermodynamic activation parameters such as ${\Delta}G^0$, ${\Delta}S^0$ and ${\Delta}H^0$ were also calculated and results were evaluated. As result montmorillonite clay was found as effective low cost adsorbent for removal of cationic dyes from waste waters.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.677-681
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• 1999

For the binary cyclohexanol-cyclohexanone system the vapor-liquid equilibrium data, which are the necessary ones for the design of the distillation columns in separation process of volatile liquid-mixtures, are measured at subatmospheric pressure of 150, 300 and 500 mmHg. An empirical relation between logarithmic values of relative volatility(log $\alpha$) and liquid phase composition(x), which predicts the vapor-liquid equilibrium data, is obtained from above measured data of 150, 300 and 500 mmHg and the published ones of 30, 100, 200, 395 and 750 mmHg. The predicted data are compared with the measured and published ones to be in good agreement.

• Resources Recycling
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• v.27 no.5
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• pp.9-13
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• 2018

The equilibrium constant of a chemical reaction is related to the standard Gibbs free energy change. Since equilibrium constant is defined as the ratio of the activities of the chemical species, it is necessary to consider the non-ideal behavior of the solutes as ionic strength of the solution increases. In this paper, the derivation of Debye-$H{\ddot{u}}ckel$ limiting law and its modification by which the activity coefficient of an ion can be calculated was explained. Moreover, the method to obtain the activity coefficient of an ion from the experimentally determined mean activity coefficients of an electrolyte was explained.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2471-2476
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• 2014

The aim of the present study is to explore the possibility of utilizing loess for the adsorption of total phosphorous (T-P) and total nitrogen (T-N) in water. Batch adsorption studies were performed to evaluate the influences of various factors like initial concentration, contact time and temperature on the adsorption of T-P and T-N. The adsorption data showed that loess is not effective for the adsorption of T-N. However, loess exhibited much higher adsorption capacity for T-P. At concentration of $1.0mgL^{-1}$, approximately 97% of T-P adsorption was achieved by loess. The equilibrium data were fitted well to the Langmuir isotherm model. The pseudo-second-order kinetic model appeared to be the better-fitting model because it has higher $R^2$ compared with the pseudo-first-order and intra-particle kinetic model. The theoretical adsorption equilibrium $q_{e,cal}$ from pseudo-second-order kinetic model was relatively similar to the experimental adsorption equilibrium $q_{e,exp}$. The thermodynamic parameters such as free energy ${\Delta}G$, the enthalpy ${\Delta}H$ and the entropy ${\Delta}S$ were also calculated.

• Advances in environmental research
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• v.1 no.2
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• pp.167-179
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• 2012

Pistachio shell (Pistacia vera) (PS), a low-cost material, has been utilized for the removal of the Cr(VI) ions after treatment with citric acid. Batch experimental steps were applied to obtain Cr(VI) ion adsorption details for the equilibrium between Cr(VI) and modified pistachio shell (MPS). The influences of contact time, pH, adsorbent dose and initial chromium concentration on the adsorption performance of MPS was investigated in detail. The results displayed that adsorption of Cr(VI) by MPS reached to equilibrium after 2 h and after that a little change of Cr(VI) removal efficiency was observed. The sorption percent is higher at lower pH and lower chromium concentration. Two possible mechanisms for reduction of Cr(VI) to Cr(III) can be suggested in Cr(VI) removal. In the first mechanism, Cr(VI) is reduced to Cr(III) by surface electron-donor groups of the adsorbent and the reduced Cr(III) forms complexes with adsorbent or remains in the solution. This Cr(III) is not adsorbed by adsorbent at pH 1.8. But in second mechanism, the adsorption-coupled reduction of Cr(VI) to Cr(III) occurred on the adsorbent sites. The equilibrium sorption capacity of Cr(VI) ion after 2 h was 64.35 mg/g for MPS.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.931-936
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• 2003

By the use of multi-loop thermodynamic boxes developed here by us, we show that models of enzyme catalysis (e.g., split-site model) developed in an attempt to emphasize the importance of the reactant-state destabilization and, thus, demonstrate misleading nature of the fundamentalist position which defines Pauling's transition-state stabilization as the entire and sole source of enzyme catalytic power, should be reduced to the fundamentalist formulation which completely neglects dynamical aspects of mechanism between the reactant and the transition states and dwells only on events restricted to the reactant and transition states alone, because the splitsite (and other canonical) formulations as well as fundamentalist formulations are based, in common, on equilibrium assumptions stipulated by the thermodynamic box logics. We propose to define the equilibrium assumptions as the requisite and sufficient conditions for the fundamentalist position to enjoy its primacy as central dogma, but not as sufficient conditions for its validity, because it is subjected to contradictions presented by existing data.

• Bulletin of the Korean Chemical Society
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• v.2 no.2
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• pp.37-41
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• 1981

The elution behaviors of molybdate and tungstate through anion exchange column have been investigated in the various concentration of hydrochloric and perchloric acid. A discussion is made to evaluate the existing these equilibrium and constant according to acidity. In both acids of 0.01-2.0 M concentration range, the existing equilibrium for molybdate and its constant calculated at $20^{\circ}C$ is $10^{18.9}$ for $Mo_8O_2^{4-} + 20H^+ {\rightleftharpoons} 8MoO_2^{2+} + 10H_2O$. In the 3-3.5 M hydrochloric acid it is 0.16 for $MoO_2Cl_2 + Cl^- {\rightleftharpoons} MoO_2Cl^{3-}$ and for the case of tungstate, in the both acids of 0.01-1.0 M concentration range $10^{6.6}$ for $W_{12}O_{39}^{6-} + 6H^+ {\rightleftharpoons} 12WO_3{\cdot}3H_2O$. In higher concentration than 1.0 M both acids the following equilibrium seems to be existed. $12WO_3{\cdot}3H_2O {\rightleftharpoons} 12WO_3 + 3H_2O$

• Journal of Hydrogen and New Energy
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• v.13 no.1
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• pp.42-51
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• 2002

Methane can be converted directly to hydrogen by pyrolysis. The reaction is highly endothemic and heat must be supplied at high temperatures. Gibbs free energy minimization calculations have been carried out for the methane pyrolysis to determine equilibrium products. The calculation parameters are the temperature, the initial H/C ratio, the pressure and Gibbs energies of each substance. Methane, ethylene, acetylene, benzene, naphthalene, and hydrogen are the main products. Excluding hydrogen, it is observed that ethylene and aromatics(benzene+naphthalene) are predominant products below 1400K, whereas acetylene is significantly formed above 1400K. Hydrogen dilution increases the selectivities for ethylene and acetylene and decreases the selectivity for aromatics. Increasing the pressure also decreases the decomposition of methane.

• Journal of Environmental Science International
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• v.15 no.7
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• pp.695-699
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• 2006

This study is to investigate the relationship between pore structures of activated carbons and adsorption characteristics of toluene vapor using dynamic adsorption method. The surface areas of below $10{\AA}$ in the pore diameter of activated carbons used in this experiment were in the range of 72 -93 % of total cumulative surface area and the toluene vapor equilibrium adsorption capacities were in the range of 350 - 390mg/g. Activated carbons having larger toluene adsorption capacity than the compared activated carbons had relatively pores in the pore diameter range of $7-10{\AA}$. Linear relationship between equilibrium adsorption capacity and cumulative sur- face area was in the diameter range of over $7{\AA}$. It was thought that toluene vapor was relatively well adsorbed on surfaces of pores of over $7{\AA}$.