• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.477-480
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• 2007

Hydrate phase equilibrium for the binary CO2+water and CH4+water mixtures in silica gel pore of nominal 6, 30, and 100 nm were measured and compared with the cacluated results based on van der Waals and Platteeuw model. At a specific temperature three-phase hydrate-water-vapor (HLV) equilibrium curves for pore hydrates were shifted to the higher-pressure condition depending on pore sizes when compared with those of bulk hydrates. Notably, hydrate phase equilibria for the case of 100 nominal urn pore size were nealy identical with those of bulk hydrates. The activities of water in porous silica gels were modified to account for capillary effect, and the calculation results were generally in good agreement with the experimental data.

• 신재생에너지
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• 제3권2호
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• pp.47-52
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• 2007

Hydrate phase equilibrium for the binary $CO_{2}$+water and $CH_{4}$+water mixtures in silica gel pore of nominal 6, 30, and 100 nm were measured and compared with the cacluated results based on van der Waals and Platteeuw model. At a specific temperature three-phase hydrate-water-vapor (HLV) equilibrium curves for pore hydrates were shifted to the higher-pressure condition depending on pore sizes when compared with those of bulk hydrates. Notably, hydrate phase equilibria for the case of 100 nominal nm pore size were nearly identical with those of bulk hydrates. The activities of water in porous silica gels were modified to account for capillary effect, and the calculation results were generally in good agreement with the experimental data.

• Bulletin of the Korean Chemical Society
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• 제19권2호
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• pp.218-222
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• 1998

Removal of Cd(Ⅱ), Zn(Ⅱ) and Cu(Ⅱ) from aqueous solutions using the adsorption process on magadiite has been investigated. It was found that the removal percentage of metal cations at equilibrium increases with increasing temperature, and follows the order of Cd(Ⅱ) > Cu(Ⅱ) > Zn(Ⅱ). Equilibrium modeling of adsorption showed that the adsorptions of Cd(Ⅱ), Cu(Ⅱ), and Zn(Ⅱ) were fitted to Langmuir isotherm. Kinetic modeling of the adsorption showed that first order reversible kinetic model fitted to experimental data. From kinetic model and equilibrium data, the overall rate constant (k) and the equilibrium constant (K) for the adsorption process were calculated. The overall rates of adsorption of metal ions follow the order of Cd(Ⅱ) > Cu(Ⅱ) > Zn(Ⅱ). From the results of thermodynamic analysis, standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) of adsorption process were calculated.

• 공업화학
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• 제24권3호
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• pp.327-332
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• 2013

입상 활성탄에 대한 bismarck brown R의 흡착평형, 동력학 및 열역학 파라미터들을 회분식 실험을 통해 살펴보았다. 조작변수로서 초기농도, 접촉시간과 흡착온도의 영향을 조사하였다. 흡착평형자료는 선형회귀법을 사용하여 Langmuir와 Freundlich 흡착등온식에 대한 적합성을 평가하였다. 흡착평형은 Freundlich 흡착등온식이 더 잘 맞았으며, 계산된 분리계수(1/n) 값으로부터 입상 활성탄이 bismarck brown R을 효과적으로 처리할 수 있다는 것을 알 수 있었다. 동력학적 실험으로부터, 흡착공정은 유사이차반응속도식에 잘 맞으며, 속도상수($k_2$) 값은 온도가 증가할수록 증가하였다. 활성화에너지, 엔탈피, 엔트로피 및 Gibbs 자유에너지변화와 같은 열역학 파라미터들은 흡착공정의 특성을 평가하기 위하여 298~318 K의 온도 범위에서 조사하였다. 활성화 에너지의 계산값은 100 mg/L에서 8.73 kJ/mol로 입상 활성탄에 대한 bismarck brown R의 흡착이 물리적 공정임을 나타냈다. Gibbs 자유에너지변화의 음수값(${\Delta}G$ = -2.59~-4.92 kJ/mol)과 엔탈피변화의 양수값(${\Delta}H$ = +26.34 kJ/mol)은 흡착공정이 자발적이며 흡열과정으로 일어난다는 것을 나타냈다.

• 대한화학회지
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• 제23권4호
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• pp.187-197
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• 1979

ChIoroform과 chloroethanol 혼합용매속에서 Poly(cis-5-methylproIine)의 광회전을 측정하였다. 이 혼합용매속에 chloroethanol이 0.5∼10부피%일때 형태 A와 B사이에는 평형상태가 이루어졌다. 광회전을 이용하여 5, 25 및 45$^{circ}$C에서 평형정수를 측정하고 자유엔탈피, 엔탈피 및 엔트로피 변화를 계산하였다. 같은 몰수의 형태 A와 B에서 출발하면 chloroethanol이 3부피% 이상일때는 정방향 변광회전이 일어나고 이하일때는 역방향 회전이 일어났다. 엔탈피와 엔트로피 변화는 정방향 변광회전일때는 양수이고 역방향 변광회전일 때는 음수였다. 반응 추진역은 정방향 회전일때는 엔트로피의 증가이고 역방향 회전일때는 엔탈피의 감소였다. 측정된 열역학적 자료들은 폴리머와 용매사이의 상호작용 즉 용매중의 chloroethanol이 형태 B분자내의 카보닐기와 선택적으로 수소결합을 형성하며, 형태 A와 B의 헝태 에너지 차이에 있다는것을 설명한다

• 분석과학
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• 제22권2호
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• pp.159-165
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• 2009

기능성 염료의 일종인 fluoran계 염료의 열 변색현상으로부터 열역학적인 함수들을 구하였다. 양성자성 용매와 비양성자성 용매에서 온도변화에 따른 UV-Vis 스펙트럼을 측정함으로서 평형상수와 엔탈피 값을 측정하였다. 양성자성 용매에서는 락톤형으로만 존재하나 비양성자성 용매에서는 락톤형과 쯔비터 이온형이 같이 존재함을 확인하였다. 평형 상수를 결정하는 요인은 용매의 극성도가 아니라 수소결합 주게의 성질에 큰 영향을 받음을 확인하였다. 엔탈피 변화량도 측정하였다. 온도 변화에 따라 열 변색 현상이 잘 일어나므로 엔탈피 변화량은 약 -2.0 kJ/mol정도이며, 따라서 열린형이 닫힌형보다도 에너지가 안정함을 확인하였다. 산에 의한 엔탈피 변화량은 양성자성 용매에서는 거의 0 kJ/mol에 가까우며 비양성자성 용매에서는 일정한 경향성을 찾기 어려웠으며. 또한 엔트로피와 깁스 자유에너지도 일정한 경향성을 보이지 않았다. 이러한 열역학적인 분석 결과는 기능성 염료의 디자인이나 합성에서 중요한 정보를 제공할 수 있다.

• 한국응용과학기술학회지
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• 제18권4호
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• pp.325-331
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• 2001

The critical micelle concentration (CMC) at which micelles start to form from a surfactant solution is usually measured in terms of conventional concentration units. However, the thermodynamic potentials are expressed in terms of mole fraction $X_{CMC}$ and $X_{CMC}$ cannot be directly measured experimentally. The Gibbs free energy, ${\Delta}G^{\ast}_{mic}$, in particular is related to $X_{CMC}$ through ${\Delta}G^{\ast}_{mic}$ = $RTlnX_{CMC}$. When it comes to CMC, the molar CMC, $C_{CMC}$, differs only by the proportionality $C^{-1}_{w}$ with $C_{w}$ being the molarity of water. Hence, $C_{CMC}$ is found to be a proper representation of CMC. However, in calculation of ${\Delta}G^{\ast}_{mic}$ and other thermodynamic potentials from the CMC, $X_{CMC}$ or $C_{CMC}/C_{w}$ should be used.

• Korean Chemical Engineering Research
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• 제62권2호
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• pp.173-180
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• 2024

Under ordinary atmospheric circumstances, the gravimetric technique was used to measure the solubility of L-cysteine (L-Cys) and L-alanine (L-Ala) in various solvents, including methyl alcohol, ethyl acetate, and mixtures of the two, in the range o 283.15 K to 323.15 K. Both individual solvents and their combinations showed a rise in the solubility of L-Cys and L-Ala with increasing temperature, according to the analyzed data but when analyzed at a constant temperature in the selected mixed solvents, the solubility declined with decreasing of initial mole fractions of methyl alcohol. To further assess, the relative utility of the four solubility models, we fitted the solubility data using the Jouyban-Acree (J-A), van't Hoff-Jouyban-Acree (V-J-A), Apelblat-Jouyban-Acree (A-J-A), and Ma models followed by evaluation of the values of the RAD information criteria and the RMSD were. The dissolution was also found to be an entropy-driven spontaneous mixing process in the solvents since the thermodynamic parameters of the solvents were determined using the van't Hoff model. In order to support the industrial crystallization of L-cysteine and L-alanine and contribute to future theoretical research, we have determined the experimental solubility, correlation equations, and thermodynamic parameters of the selected amino acids during the dissolution process.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2004년도 학술논문집
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• pp.105-114
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• 2004

This study investigated the thermal behavior of the nuclear graphite waste generated from the decommissioning of the Korean nuclear research reactor, The first part study investigated the decomposition rate of the nuclear graphite waste up to $1000^{\circ}C$ under various oxygen partial pressures using a thermo-gravimetric analyzer (TGA). Tested graphite waste sample not easily destroyed in the oxygen-deficient condition. However, the gas-solid oxidation reaction was found to be very effective in the presence of oxygen. No significant amount of the product of incomplete combustion was formed even in the limited oxygen concentration of 4% $O_2$. The influence of temperature and oxygen partial pressure was evaluated by the theoretical model analysis of the thermo-gravimetric data. The activation energy and the reaction order of graphite oxidation were evaluated as 128 kJ/mole and 1.1, respectively. The second part of this study investigated the behavior of radioactive elements under graphite oxidation atmosphere using thermodynamic equilibrium model. $^{22}Na$, $^{134}Cs$ and $^{137}Cs$ were found be the semi-volatile elements. Since volatile uranium species can be formulated at high temperatures above $1050^{\circ}C$, the temperature of incinerator furnace should be minimized. Other corrosion/activation products, fission products and uranium were found to be the non-volatile species.

• 한국수소및신에너지학회논문집
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• 제13권1호
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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.