• KSBB Journal
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• 제13권2호
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• pp.162-167
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• 1998

The adsorption behaviors of two major cellulase components, endo I and exo II, from Trichoderma viride were investigated using $\alpha$-celluloses with different correlation crystallinity index(Cc) as substrates. The adsorption of cellulase enzyme components was significantly affected by the reaction condition and the physicochemical properties of the cellulose. The $\alpha$-cellulose was hydrolyzed in the presence of cellulase for various periods. The correlation crystallinity index of $\alpha$-cellulose increased with increasing the hydrolysis time. The adsorption was apparently found to obey the first-order kinetics, and the adsorption activation energy(Ea) was calculated from the adsorption rate constant(ka). The value of adsorption rate constant for endo I was larger than that of exo II. This means that endo I are adsorbed more rapidly than exo II. With the increase in correlation crystallinity index, the values of the adsorption rate constants for endo I and exo II decreased, respectively. The activation energy for the adsorption of exo II on the cellulose also was larger than that of endo I. Also adsorption activation energy of endo I and exo II increased with an increase in the crystallinity of sample cellulose.

• Bulletin of the Korean Chemical Society
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• 제11권3호
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• pp.231-235
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• 1990

The activation energy of dissociative adsorption of oxygen on polycrystalline nickel surface is calculated from adsorption isotherms obtained using X-ray photoelectron spectroscopy. Negative value of this activation energy (-5.9 kJ/mol) indicates that the adsorption takes place through an undissociated precursor state. An adsorption energy for this precursor state is calculated assuming the precursor state as a moleculary physisorbed state ($E_{ad}$ = -7.9 kJ/mol). Finally, an adsorption isotherm equation is derived as a function of the gas exposure, which agrees with the experimental isotherms reasonably good.

• Current Applied Physics
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• 제18권12호
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• pp.1528-1533
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• 2018

The trajectories of adsorption and dissociation process of $O_2$ on the Al (111) surface were studied by the spinpolarized ab initio molecular dynamics method, and the adsorption activation energy was clarified by the NEB method with hybrid functionals. Three typical dissociation trajectories were found through simulation of $O_2$ molecule at different initial positions. When vertically approaches to the Al surface, the $O_2$ molecule tends to rotate, and the activation energy is 0.66eV. If $O_2$ molecule does not rotate, the activation energy will increase to 1.43 eV, and it makes the O atom enter the Al sublayer eventually. When the $O_2$ molecules parallel approach to the Al surface, there is no activation energy, due to the huge energy released during the adsorption process.

• 자원리싸이클링
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• 제12권3호
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• pp.13-24
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• 2003

폐호도껍질을 원료로 활성탄을 제조하는 과정에서 활성화 온도, 활성화 시간, 활성화제의 양, 그리고 활성화제의 종류 등을 변수로 하여 활성화 특성을 조사하였다. 인산을 활성화제로 사용하여 제조된 활성탄은 그 흡착능이 온도가 증가함에 따라 증가하여 약 $550^{\circ}C$부근에서 최대 흡착능을 보였으며 그 수율은 온도 상승에 따라 지속적으로 감소하였다. 활성화 시간은 약 2시간 정도에서 최적의 조건을 보였으며 시간이 증가함에 따라 활성탄의 수율은 계속 감소하였다. 활성화제의 농도 증가에 따라 수율은 지속적으로 상승하였으며 흡착능 또한 증대되다가 약 1.5M $H_3PO_4$ 이상의 조건에서는 오히려 흡착능이 감소하였다. SEM으로 관찰한 조건에 따른 활성탄의 미세구조의 변화는 조건별 흡착능의 변화와 잘 일치되었으며 활성화제의 종류는 활성화 과정에서 중요한 영향을 미치는 것으로 조사되었다. 제조된 활성탄의 흡착특성을 파악하기 위해 $Cu^{2+}$ 이온을 흡착질로 하여 흡착반응을 조사한 결과, 흡착반응은 전체적으로 2차식을 따르는 것으로 관찰되었으며 흡착질의 초기 농도가 감소함에 따라 반응상수는 점차 증가하였다. 평형흡착량은 Freundlich Model 을 잘 따르는 것으로 나타났으며 온도별 흡착반응을 검토한 결과, 중금속 이온의 흡착은 흡열반응의 특성을 나타내었다. 흡착에 따른 Activation Energy는 약 13.07kcal/mol로 산출되었으며 van't Hoff Equation을 이용하여 흡착반응의 열역학적 인자들을 계산하였다.

• 에너지공학
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• 제13권2호
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• pp.166-172
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• 2004

The activated carbon was produced from Sancheong bamboo by steam and carbon dioxide gas activation methods. The carbonization of raw material was conducted at 90$0^{\circ}C$ and gas activation reactions were conducted with respect to various conditions. -activation temperature 750-90$0^{\circ}C$, the flow rate of steam 0.5-2g-$H_2O$/g-char$.$hr, the flow rate of carbon dioxide 5-30$m\ell$-$CO_2$/g-char-min and activation time 1-5 hr. The prepared activated carbons were measured yield, the adsorption capacity of iodine and methylene blue, BET specific surface area and pore size distribution. The adsorption capacity of iodine (680.5-1526.1 mg/g) and methylene blue (18.3-221.5 mg/g) increased with creasing activation temperature and activation time. The adsorption capacity of iodine and methylene blue increased with the activation gas quantity in the range of 0.5-1.5g-$H_2O$/g-charㆍhr, 5-18.9$m\ell$-Co$_2$/g-charㆍmin. But those decreased over those range due to the pore shrinkage. The steam activation method was superior in efficiency to carbon dioxide activation method.

• Bulletin of the Korean Chemical Society
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• 제19권7호
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• pp.733-737
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• 1998

Using an atom superposition and electron delocalization molecular orbital (ASED-MO) method, we have compared adsorption properties of adsorbates on the Pt(Ill) surface with the Pt(lll)/γ-Al203 surface in the ethylene hydrogenation reaction. In two-layer thick model systems, the calculated activation energy of the hydrogenation by the surface platinum hydride is equal to the energy by the hydride over supported platinum/γ-alumina. The transition structure on platinum is very close to the structure on the supported platinum/γ-alumina surface. Hydrogenation by the surface hydride on platinum can take place easily because the activation energy is about 0.5 eV less than hydrogenation by ethylidene. On supported platinum/,y-alumina the activation energy of the hydride mechanism is about 0.61 eV less than that of ethylidene mechanism. In one-layer thick model systems, the activation energy of hydrogenation by ethylidene is about 0.13 eV less than the activation energy of hydride reaction. The calculated activation energy by the hydride over the supported platinum y-alumina is 0. 24 eV higher than the platinum surface. We have found from this result that the catalytic properties of one-layer thick model systems have been influenced by the support but the two-layer thick model systems have not been influenced by the support.

• Journal of the Korean Wood Science and Technology
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• 제20권4호
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• pp.21-30
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• 1992

An activation energy equation for moisture diffusion in wood was developed with an assumption that activation energy is directly proportional to wood specific gravity. Theoretical activation energies obtained from the activation energy equation were revealed to be always lower than actual activation energies, which implies that activation energy isn't affected only by wood specific gravity. The other affecting factors are possibly anatomical structures of wood which determine a ratio of vapor diffusion to bound water diffusion in wood. For the convenience of estimating actual activation energy by using the activation energy equation, thirteen kinds of species were categorized into three groups according to their anatomical structures.

• Korean Chemical Engineering Research
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• 제58권3호
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• pp.458-465
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• 2020

활성탄에 의한 acid fuchsin (AF) 염료의 흡착에 대한 등온선, 동력학 및 열역학적 특성치를 흡착제의 양, pH, 초기 농도, 접촉시간 및 온도를 변수로 하여 수행하였다. 활성탄을 사용한 AF의 흡착에 대한 pH의 영향은 산성(pH 8)에서 흡착백분율이 높은 욕조 현상을 나타냈다. 등온흡착 데이터는 Freundlich, Langmuir, Dubinin-Radushkevich 등온흡착식에 맞춰 보았다. Freundlich 식이 가장 높은 일치도를 나타냈으며, 흡착메카니즘이 다분자층 흡착임을 알았다. 흡착용량은 온도증가와 함께 증가하였다. Freundlich의 분리계수는 이 흡착공정이 적합한 처리공정임을 나타냈다. Dubinin-Radushkevich 등온흡착식에 의해 평가된 흡착 에너지는 활성탄에 의한 AF의 흡착이 물리 흡착임을 확인시켰다. 흡착동력학은 유사이차반응속도식에 잘 맞았다. 입자내 확산 모델에 의해 흡착점에서의 표면 확산이 율속단계로 평가되었다. 흡착공정의 활성화 에너지와 엔탈피 변화는 각각 21.19 kJ/mol, 23.05 kJ/mol 이었다. Gibbs 자유 에너지 변화는 흡착반응이 온도가 높아질수록 자발성이 더 진다는 것을 알려주었다. 양의 엔트로피는 이공정이 비가역적이라는 것을 나타냈다. 등량 흡착열은 본질덕으로 물리흡착임을 나타냈다.

• Corrosion Science and Technology
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• 제21권5호
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• pp.381-389
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• 2022

Cyclic Voltammetry and weight loss measurements were used to investigate corrosion prevention of tin in a 0.5M citric acid solution containing Anthocyanins extracted from grapes at various concentrations and temperatures. Results showed that the investigated chemicals, Anthocyanins extracted from grapes, performed well as tin corrosion inhibitors in 0.5M citric acid. Increasing the concentration of Anthocyanins increased their corrosion inhibition efficiencies. When the temperature dropped, their inhibition efficiencies, increased indicating that higher temperature tin dissolution predominated the adsorption of Anthocyanins at the surface of tin metal. When inhibitor concentrations were increased, their inhibition efficiencies were also increased. These results revealed that corrosion of tin metal was inhibited by a mixed type of adsorption on the metal surface. The adsorption isotherm of Langmuir governed the adsorption of Anthocyanins. Thermodynamic parameters such as the enthalpy of adsorption, the entropy of adsorption, and Gibbs free energy and kinetic parameters such as activation energy, enthalpy of activation, and entropy of activation were computed and discussed in this study.

• 청정기술
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• 제18권1호
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• pp.76-82
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• 2012

폐수로 부터 유독한 말라카이트 그린 성분을 제거하는데 있어서 제올라이트의 활용가능성을 살펴보았다. 흡착실험은 298, 308 및 318 K에서 수행하였으며, 흡착에 대한 온도, 접촉시간과 초기농도의 영향을 조사하였다. 흡착자료를 기초로 Langmuir와 Freundlich 흡착등온식에 대한 적합성을 평가하였다. 흡착공정은 Freundlich 흡착등온식이 잘 맞았으므로 제올라이트 표면의 불균일한 에너지에 의해 선택적인 흡착이 이루어짐을 알았다. 계산된 흡착등온선의 상수 값으로부터 제올라이트에 의해서 말라카이트 그린의 효과적인 처리가 가능하다는 것을 알 수 있었다. 동력학적 실험으로부터, 흡착공정은 유사이차반응속도식에 잘 맞으며, 속도상수($k_2$) 값은 말라카이트 그린의 초기농도가 증가할수록 감소하였다. 활성화에너지, 엔탈피, 엔트로피 및 자유에너지변화와 같은 열역학 파라미터들은 흡착공정의 특성을 평가하기 위하여 조사하였다. 활성화에너지의 계산값은 제올라이트에 대한 말라카이트 그린의 흡착이 물리적 공정임을 나타냈다. 자유에너지변화값(${\Delta}G^{\circ}$ = -6.47~-9.07 kJ/mol)과 엔탈피변화값(${\Delta}H^{\circ}$ = +32.414 kJ/mol)은 흡착공정이 298~318 K 범위에서 자발적이고 흡열과정이라는 것을 나타냈다.