• 전기화학회지
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• 제10권3호
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• pp.219-228
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• 2007

The phase-shift method and correlation constants, i.e., the electrochemical impedance spectroscopy (EIS) techniques for studying linear relationships between the behaviors (${\varphi}\;vs.\;E$) of the phase shift ($0^{\circ}{\leq}-{\varphi}{\leq}90^{\circ}$) for the optimum intermediate frequency and those (${\theta}\;vs.\;E$) of the fractional surface coverage ($1{\geq}{\theta}{\geq}0$), have been proposed and verified to determine the Langmuir, Frumkin, and Temkin adsorption isotherms (${\theta}\;vs.\;E$) of H for the cathodic $H_2$ evolution reaction (HER) at noble and transition-metal/aqueous solution interfaces. At the Pt/0.1 MKOH aqueous solution interface, the Langmuir, Frumkin, and Temkin adsorption isotherms (${\theta}\;vs.\;E$), equilibrium constants ($K=5.6{\times}10^{-10}\;mol^{-1}\;at\;0{\leq}{\theta}<0.81$, $K=5.6{\times}10^{-9}{\exp}(-4.6{\theta})\;mol^{-1}\;at\;0.2<{\theta}<0.8$, and $K=5.6{\times}10^{-10}{\exp}(-12{\theta})\;mol^{-1}\;at\;0.919<{\theta}{\leq}1$, interaction parameters (g = 4.6 for the Temkin and g = 12 for the Frumkin adsorption isotherm), rates of change of the standard free energy ($r=11.4\;kJ\;mol^{-1}$ for g=4.6 and $r=29.8\;kJ\;mol^{-1}$ for g=12), and standard free energies (${\Delta}G_{ads}^0=52.8\;kJ\;mol^{-1}\;at\;0{\leq}{\theta}<0.81,\;49.4<{\Delta}G_{\theta}^0<56.2\;kJ\;mol^{-1}\;at\;0.2<{\theta}<0.8$ and $80.1<{\Delta}_{\theta}^0{\leq}82.5\;kJ\;mol^{-1}\;at\;0.919<{\theta}{\leq}1$) of OH for the anodic $O_2$ evolution reaction (OER) are also determined using the phase-shift method and correlation constants. The adsorption of OH transits from the Langmuir to the Frumkin adsorption isotherm (${\theta}\;vs.E$), and vice versa, depending on the electrode potential (E) or the fractional surface coverage (${\theta}$). At the intermediate values of ${\theta}$, i.e., $0.2<{\theta}<0.8$, the Temkin adsorption isotherm (${\theta}\;vs.\;E$) correlating with the Langmuir or the Frumkin adsorption isotherm (${\theta}\;vs.\;E$), and vice versa, is readily determined using the correlation constants. The phase-shift method and correlation constants are accurate and reliable techniques to determine the adsorption isotherms and related electrode kinetic and thermodynamic parameters. They are useful and effective ways to study the adsorptions of intermediates (H, OH) for the sequential reactions (HER, OER) at the interfaces.

• 전기화학회지
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• 제12권1호
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• pp.26-33
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• 2009

The phase-shift method and correlation constants, i.e., the unique electrochemical impedance spectroscopy (EIS) techniques for studying the linear relationship between the behavior ($-{\varphi}$ vs. E) of the phase shift ($90^{\circ}{\geq}-{\varphi}{\geq}0^{\circ}$) for the optimum intermediate frequency and that ($\theta$ vs. E) of the fractional surface coverage ($0{\leq}{\theta}{\leq}1$), have been proposed and verified to determine the Langmuir, Frumkin, and Temkin adsorption isotherms of H and related electrode kinetic and thermodynamic parameters at noble metal (alloy)/aqueous solution interfaces. At a Zr/0.2 M ${H_2}{SO_4}$ aqueous solution interface, the Frumkin and Temkin adsorption isotherms ($\theta$ vs. E), equilibrium constants (K = $1.401{\times}10^{-17}\exp(-3.5{\theta})mol^{-1}$ for the Frumkin and K = $1.401{\times}10^{-16}\exp(8.1{\theta})mol^{-1}$ for the Temkin adsorption isotherm), interaction parameters (g = 3.5 for the Frumkin and g = 8.1 for the Temkin adsorption isotherm), rates of change of the standard free energy (r = $8.7\;kJ\;mol^{-1}$ for g = 3.5 and r = $20\;kJ\;mol^{-1}$ for g = 8.1) of H with $\theta$, and standard free energies ($96.13{\leq}{\Delta}G^0_{\theta}{\leq}104.8\;kJ\;mol^{-1}$ for K = $1.401{\times}10^{-17}\exp(-3.5{\theta})mol^{-1}$ and $0{\leq}{\theta}{\leq}1$ and ($94.44<{\Delta}G^0_{\theta}<106.5\;kJ\;mol^{-1}$ for K = $1.401{\times}10^{-16}\exp(-8.1{\theta})mol^{-1}$ and $0.2<{\theta}<0.8$) of H are determined using the phase-shift method and correlation constants. At 0.2 < $\theta$ < 0.8, the Temkin adsorption isotherm correlating with the Frumkin adsorption isotherm, and vice versa, is readily determined using the correlation constants. The phase-shift method and correlation constants are probably the most accurate, useful, and effective ways to determine the adsorption isotherms of H and related electrode kinetic and thermodynamic parameters at highly corrosion-resistant metal/aqueous solution interfaces.

• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1549-1553
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• 2008

A molecular imprinted polymer (MIP) using (+)catechin ((+)C) as a template and acrylamide (AM) as a functional monomer was prepared. Acetonitrile was used as the porogen with ethylene glycol dimethacrylate (EGDMA) as the crosslinker and 2,2'-azobis(isobutyronitrile) (AIBN) as the initiator. The adsorption isotherms in the MIP were measured and the parameters of the equilibrium isotherms were estimated by linear and nonlinear regression analyses. The linear equation for original concentration and adsorpted concentrations was then expressed, and the adsorption equilibrium data were correlated into Langmuir, Freundlich, quadratic, and Langmuir Extension isotherm models. The mixture compounds of (+)C and epicatechin (EC) show competitive adsorption on specific binding sites of the (+)catechin-MIP. The adsorption concentrations of (+)C, epicatechin (EC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG), on the (+)catechin-molecular imprinted polymer were compared. Through the analysis, the (+)catechin-molecular imprinted polymer showed higher adsorption ability than blank polymer which was synthesized molecular imprinted polymer without (+)catechin. Furthermore, the competitive Langmuir isotherms were applied to the mixture compounds of (+)C and EC.

• 한국환경농학회지
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• 제24권2호
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• pp.123-131
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• 2005

살균제 procymidone의 토양 중 행적에 관한 흡 탈착, 용탈실험과 광분해 및 가수분해 실험을 통한 농업환경 중 동태를 구명코자 하였으며, 그 결과는 다음과 같다. 흡착은 직선식과 Freundlich식에 부합하였고, 분배계수는 $2.75{\sim}12.18$, Kf값은 $1.99{\sim}9.98$로 토양유기물 함량에 비례하였다. 토양별 탈착율은 백산>지곡>남계통의 순서로 높게 나타났다. 자연광 하에서의 광분해는 느려 자연광에 의한 직접적인 분해는 적을 것으로 사료되었으며, 용탈 이동성은 낮아 Macall총설 및 SSLRC 이동성 분류에 따라 low class에 속했고 특히 유기물 함량이 높은 남계통은 2주 경과후에도 농약이 용탈되지 않았다. 가수분해 실험결과 procymidone은 산성 및 중성보다 알칼리 조건에서 가수분해가 빨랐으며, 높은 온도에서 분해가 빨랐다. 이상의 결과 procymidone은 토양환경에서 흡착량이 높고 이동성이 낮아 타 환경계로의 전이 정도는 매우 낮다고 평가되었다.

• 청정기술
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• 제7권2호
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• pp.127-132
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• 2001

수소 등 다성분 혼합가스로부터 고순도의 수소를 얻기 위한 PSA 조업에 있어서 흡착탑 내 활성탄 층 충전길이의 효과를 연구하였다. 기-고상 간 물질전달은 LDF 식을 사용하였고 각 조성물질의 비선형 흡착등온선으로 변형 Langmuir 식을 사용하였다. 각각 다른 흡착성능을 가진 활성탄과 제올라이트 2개의 흡착제를 한 개의 흡착탑 내에 연속 충전시킨 결과 제품의 순도와 회수율 면에서 흡착제의 충전길이 비가 매우 중요하였다. 120 cm인 흡착탑 내 최적의 활성탄 층 길이는 $CO_2$ 농도가 최종 제거되는 부위로 결정되는데 이 때 제품의 최고 순도를 나타내는 지점이 65cm였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제9권1호
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• pp.63-69
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• 2004

금속광산 일대의 비소오염 지중 복원기술로써 투수성 반응벽체의 흡착제로 철산화물인 적철석 피복 모래의 적용가능성을 평가했다. 이를 위해서 흡착곡선실험, 비소제거속도실험 및 컬럼내 비소 제거 실험을 통해서 철산화물 피복 모래에 의한 비소 3가와 비소 5가의 제거 효율 및 유동환경에서의 비소 제거능력에 대해 고찰하였다. 적철석 피복 모래는 1.0 mg/L 수준의 낮은 비소 농도에서 높은 흡착력을 보이는 선형 등온 흡착곡선을 보였다. 컬럼실험에서 높은 피복모래의 안은 비소제거효율을 높였으나, 비소 3가가 비소 5가보다 흡착력이 떨어지고 지하수의 유동적인 환경에서 비소의 물리적 확산 현상으로 흡착반응속도의 저하 때문에 제거양이 감소했다. 따라서, 유동적인 환경에서 피복모래의 상대적인 양, 비소화학종의 흡착력, 흡착반응속도가 제거 효율을 좌우했다.

• 한국물환경학회지
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• 제26권2호
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• pp.332-342
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• 2010

A model has been developed to investigate in-river sediment and phosphorus dynamics. This advective-dispersive model is coupled with hydrodynamics and sediment transport submodels to simulate suspended sediment, total dissolved phosphorus, total phosphorus, and particulate phosphorus concentrations under unsteady flow conditions. It emphasizes sediment and phosphorus dynamics in unsteady flow conditions, in which the study differs from many previous solute transport studies, conducted in relatively steady flow conditions. The diffusion wave approaximation was employed for unsteady flow simulations. The first-order adsorption and linear adsorption isotherm model was used on the basis of the three-layered riverbed submodel with riverbed sediment exchange and erosion/deposition processes. Various numerical methods were tested to select a method that had minimal numerical dispersion under unsteady flow conditions. The responses of the model to the change of model parameter values were tested as well.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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• pp.277-284
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• 2004

Batch experiments were conducted to investigate the sorption and desorption behaviors of PAHs (naphthalene, phenanthrene and pyrene) in soils. Three different soils montmorillonite KSF (foc =0.14%), masato (foc =0.08%), and diatomite (foc =0.007%) were investigated. The results of sorption-desorption experiment indicate that the sorption affinity of PAHs was in the order of montmorillonite > masato > diatomite. The Freundlich model was well fitted to the sorption and desorption data. Sorption affinity increased as loc increased. Desorption of PAHs from soils was biphasic composed of reversible and irreversible compartments. Desorption-resistance of phenanthrene in soils was also determined. The biphasic desorption model was used to explain desorption-resistance of phenanthrene in soils. The linear term represents reversible sorption fraction and Langmuinian-type term represents desorption-resistant fraction.

• 한국대기환경학회지
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• 제17권4호
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• pp.355-362
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• 2001

Adsorption isotherms of dichloromethane and 1, 1, 2-trichloro-1,2,2-trifluoroethane on an activated carbon pellet, Norit B4, were studied. For these chemicals, Sips equation gave the best fit for the single component adsorption isotherm. The adsorption affinity on activated carbon was greater for dichloromethane than that of 1, 1, 2-trichloro-1,2,2-trifluoroethane. An experimental and theoretical study was made for the adsorption of dichloromethane and 1, 1,2-trichloro-1,2,2-trifluoroethane in a fixed bed. Experimental results were used to examine the effect of operation variables, such as feed concentration, flow rate and bed height. Intraparticle diffusion was able to be explained by surface diffusion mechanism. An adsorption model baked on the linear driving force approximation (LDFA) was found to be applicable to fit the experimental data.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
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• pp.128-131
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• 2001

We evaluated natural attenuation of petroleum hydrocarbons in a shallow aquifer using a modeling study. The studied shallow aquifer was severely contaminated with petroleum hydrocarbons, especially toluene, ethylbenzene and xylenes (i.e, TEX). The exact spill history was not known. Therefor we used a contaminant level in May 1999 (the first sampling date of our integrated study) as an initial contaminant concentration. we calibrated required transport parameters using the contamination levels obtained from groundwater analyses in September of 1999. For fate and transport of the petroleum contaminants, five case 2 with sorption and degradation. case 3 with sorption and degradation (half decay constant compared with case 2), case 4 with degradation but no sorption, and case 5 with sorption but no degradation. For sorption and degradation, a linear sorption isotherm and first order irreversible decay was assumed, respectively and no additional contamination source to groundwater is also assumed.