• 제목/요약/키워드: Isotherms

검색결과 650건 처리시간 0.028초

Characterisation of Some Silica Samples Modified with Aluminium by Inverse Liquid Chromatography using Squalene as Probe - Part IV

  • Zhang Zhentao;Balard Henri;Donnet J. B.
    • 한국방사성폐기물학회:학술대회논문집
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    • 한국방사성폐기물학회 2005년도 Proceedings of The 6th korea-china joint workshop on nuclear waste management
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    • pp.107-116
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    • 2005
  • Precipitated silicas modified by aluminium were characterised using inverse liquid chromatography in anhydrous heptane with squalene as probes. Their monolayer capacities of adsorption, Langmuir's and Henry's constants were determined from the desorption isotherms according to frontal analysis. A narrow band consisting of isotherms was observed. The introduction of aluminium has little influence on the monolayer capacity, Langmuir's constants and the Henry constant. Experimental data show that neither the amounts of aluminium on the silica nor the methods of the introduction of aluminium into the silica influence the interactions between the squalene and the silicas.

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Isotherm for $Ni-O_2$ Adsorption System

  • Kyoung-Hee Ham;Woon-Sun Ahn
    • 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.

수소유기에 따른 Pd-Co합금들의 상 분리 현상에 대한 열역학적 고찰 (Thermodynamics of Hydrogen-Induced Phase Separation on Pd-Co Alloys)

  • 송도민;박충년;최전
    • 한국수소및신에너지학회논문집
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    • 제16권3호
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    • pp.244-252
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    • 2005
  • It is very interesting and important in the academic point of view and in practical use the hydrogen-induced phase separation(HIPS) which appears during hydrogen heat treatment. Since hydrogen can be removed very fast by pumping it out the hydrogen-induced new lattice phase which can not be obtained without hydrogen can be preserved as meta-stable state. In this study it has been investigated whether the HIPS appear in Pd-Al, Pd-Co, Pd-Cr, Pd-Ti, Pd-V and Pd-Zr alloys and discussed thermodynamic representation of the HIPS. The Pd alloys were arc-melted under argon atmosphere and remelted 4 or 5 times for homogenization. The alloys were annealed at 600$^{\circ}C$ under vacuum for 24 hrs and then subjected to pressure-composition isotherm measurements at 100$^{\circ}C$. The hydrogen heat treatment(HHT) of samples was carried out at 600$^{\circ}C$ under hydrogen pressure of 70 bar for 6 days and PC isotherms at 100$^{\circ}C$ were measured. By comparing the PC isotherms measured before and after HHT, occurrence of phase separation was determined. The experimental results showed that the HIPS appeared only in Pd-0.05Co alloy. For Pd-Co alloys with various composition the PC isotherms were measured. By adopting Park-Flanagan model for ternary thermodynamics the Gibbs free energy change for Pd-Co-H solid solution was calculated and subsequently with this the HIPS in Pd-Co alloy was explained fairly.

Frontal Analysis와 Pulse Input Method를 이용한 Loxoprofen의 등온흡착식 결정 (Determination of Loxoprofen Adsorption Isotherms by Frontal Analysis and Pulse Input Method)

  • 이은;박준섭;김인호
    • KSBB Journal
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    • 제21권5호
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    • pp.371-375
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    • 2006
  • 본 실험의 목적은 frontal analysis(FA)와 pluse input method(PIM) 방법으로 흡착분리공정에 있어서 중요한 전 단계의 하나인 등온흡착식을 결정하는데 있다. FA를 수행하기에 앞서 대상물질이었던 loxoprofen의 용해도를 측정하여 hexane/ethanol=95/5일 때 시료의 농도를 $0.2{\sim}3mg/ml$로 결정하고, pH조정을 위한 acetic acid는 0.5%로 결정하였다. 이동상의 주성분인 hexane의 조성이 증가함에 따라 용해도는 감소하였지만 분리도는 증가하는 경향을 확인하였다. 이런 용해도와 분리도 사이의 trade-off 또한 흡착분리과정에서의 조작변수가 될 수 있음을 의미한다. FA로 구한 이성분계 등온흡착식은 $$C_{S,re}=\frac{5.282C_{M,re}}{1+0.1412C_{M,re}+0.2139C_{M,ex}}$$, $$C_{S,ex}=\frac{6.413C_{M,ex}}{1+0.2139C_{M,ex}+0.1412C_{M,re}}$$로 결정하였고, PIM으로 구한 이성분계 등온흡착식은 $$C_{S,re}=\frac{5.245C_{M,re}}{1+0.1667C_{M,re}+0.2054C_{M,ex}}$$, $$C_{S,ex}=\frac{6.061C_{M,ex}}{1+0.2054C_{M,ex}+0.1667C_{M,re}}$$로 결정 하였다.

귀금속(Au, Rh) 전극계면에서 Langmuir 흡착등온식에 관한 위상이동방법 (The Phase-Shift Method for the Langmuir Adsorption Isotherms at the Noble Metal (Au, Rh) Electrode Interfaces)

  • 천장호;전상규;이재항
    • 전기화학회지
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    • 제6권2호
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    • pp.119-129
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    • 2003
  • The Langmuir adsorption isotherms of the over-potentially deposited hydrogen (OPD H) fur the cathodic $H_2$ evolution reaction (HER) at the poly-Au and $Rh|0.5M\;H_2SO_4$ aqueous electrolyte interfaces have been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift $(0^{\circ}{\leq}{-\phi}{\leq}90^{\circ})$ for the optimum intermediate frequency corresponds well to that of the fractional surface coverage $(1{\geq}{\theta}{\geq}0)$ at the interfaces. The phase-shift profile $({-\phi}\;vs.\;E)$ for the optimum intermediate frequency, i.e., the phase-shift method, can be used as a new electrochemical method to determine the Langmuir adsorption isotherm $({\theta}\;vs.\;E)$ of the OPD H for the cathodic HER at the interfaces. At the poly-Au|0.5M $H_2SO_4$ aqueous electrolyte interface, the equilibrium constant (K) and the standard free energy $({\Delta}G_{ads})$ of the OPD H are $2.3\times10^{-6}$ and 32.2kJ/mol, respectively. At the poly-Rh|0.5M $H_2SO_4$ aqueous electrolyte interface, K and ${\Delta}G_{ads}$ of the OPD H are $4.1\times10^4\;or\;1.2\times10^{-2}$ and 19.3 or 11.0kJ/mol depending on E, respectively. In contrast to the poly-Au electrode interface, the two different Langmuir adsorption isotherms of the OPD H are observed at the poly-Rh electrode interface. The two different Langmuir adsorption isotherms of the OPD H correspond to the two different adsorption sites of the OPD H on the poly-Rh electrode surface.

제올라이트: 압력순환형 흡착제로서의 특성과 CO2 흡착성능 (Zeolites: Their Features as Pressure Swing Adsorbents and CO2 Adsorption Capacity)

  • 김문현;조일흠;최상옥;추수태
    • 한국환경과학회지
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    • 제23권5호
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    • pp.943-962
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    • 2014
  • Industrial gas drying, dilute gas mixtures purification, air fractionation, hydrogen production from steam reformers and petroleum refinery off-gases, etc are conducted by using adsorptive separation technology. The pressure swing adsorption (PSA) has certain advantages over the other methods, such as absorption and membrane, that are a low energy requirement and cost-effectiveness. A key component of PSA systems is adsorbents that should be highly selective to a gas being separated from its mixture streams and have isotherms suitable for the operation principle. The six standard types of isotherms have been examined in this review, and among them the best behavior in the adsorption of $CO_2$ as a function of pressure was proposed in aspects of maximizing a working capacity upon excursion between adsorption and desorption cycles. Zeolites and molecular sieves are historically typical adsorbents for such PSA applications in gas and related industries, and their physicochemical features, e.g., framework, channel structure, pore size, Si-to-Al ratio (SAR), and specific surface area, are strongly associated with the extent of $CO_2$ adsorption at given conditions and those points have been extensively described with literature data. A great body of data of $CO_2$ adsorption on the nanoporous zeolitic materials have been collected according to pressure ranges adsorbed, and these isotherms have been discussed to get an insight into a better $CO_2$ adsorbent for PSA processes.

QSAR 방법을 이용한 가스 상태의 등온흡착선 예측 (Prediction of Gas Phase Sorption Isotherms on The Basis of QSAR Method)

  • 김종오
    • 대한토목학회논문집
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    • 제11권3호
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    • pp.11-18
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    • 1991
  • 휘발성 유기물질(VOC)은 많은 경로를 통해 발생되는데, 독성이 있을뿐 아니라 발암물질을 포함하고 있으므로, 이들 물질 제거는 매우 중요하다. 본 연구에서는 휘발성 유기물질 처리를 위해 활성탄을 사용할 경우 처리와 설계를 위해 흡착능력의 연구가 반드시 필요하다. 그러므로, 본 연구에서는 사용할 화합물에 대한 가스 상태의 등온흡착선을 물리적 특성과 액화상태의 등온흡착선으로 부터 예측하였다. 이를 위해 이용된 방법이 quantitative structure-activity relationships(QSAR) 방법이다. 가스 상태의 등온흡착선을 분자연결제수($^2{\chi}$)와 헨리의 계수, 또는 용해도와 가스 상태의 평형농도에 의해서 예측 할 수 있었다. 연구결과, Freundlich 모델을 근거로한 가스 상태의 등온흡착선은 ${\log}\;a_g=0.238\;^2{\chi}+0.573\;{\log}\;H_a+4.330(r^2=0.94)$ 이었다. 결과적으로, 저흡착능력 범위에서 Freundlich 이론을 근거로한 이 방법은 시간소비적 실험을 통하지 않고도 가스 상태의 등온흡착선을 예측할 수 있다는 것을 제시하고 있다.

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잎담배의 흡습 및 탈습에 관한 연구 (Moisture Sorption and Desorption Isotherms of Various Leaf Tobaccos)

  • 진학용;최승찬;이태호;유광근
    • 한국연초학회지
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    • 제3권1호
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    • pp.30-40
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    • 1981
  • The moisture sorption and desorption isotherms of various tobaccos were obtained over a relative humidity range from 0 to 90% at $20^{\circ}C$ and $30^{\circ}C$. The hysteresis effect, constant and rate of moisture sorption and desorption, monomolecular-layer moisture content, and specific surface area were analyzed from the obtained data. The moisture sorption and desorption isotherms showed a different characteristics for different tobacco varieties. At a lower humidity range below 50% RH, Burley tobacco had higher moisture sorption and desorption figures than Hicks and Basma, while, at a higher humidity range above 50% RH, Hicks had higher values than the others. The hysteresis effect of tobacco were greater in an intermediate humidity range (40-70% RN), and Basma showed a greater effect than the others. The sorption and desorption constant (K) increased with temperature, but decreased with RH, and Burley tobacco had larger K values, while Hicks had smaller K values than others. The sorption and desorption rate of Burley tobacco were greater than the other tobaccos. The monomolecular-layer moisture was 27.8 and 51.4mg/g, and the specific surface was 101 and $186m^2/g$, for Basma and Burley, respectively.

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혼합용매중에서의 Poly(ethylene terephthalate)섬유의 팽윤성(II) ―평형팽윤 및 수축거동― (Swelling Properties of Poly(ethylene terephthalate) Fiber in Mixed Solvent(II) ―Equilibrium Swelling and Shrinkage―)

  • Lee, Mun Cheul;Pak, Pyong Ki;Cho, Hyun Hok
    • 한국염색가공학회지
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    • 제6권4호
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    • pp.17-26
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    • 1994
  • Poly(ethylene terephthalate)(PET) filaments were treated in binary mixtures of organic solvents such as benzyl alcohol/perchloroethylene(BA/PER), benzyl alcohol/trichloroethylene(BA/TRI), benzyl alcohol/ethylene chloride(BA/EC), methanol/perchloroethylene (ME/PER), and methanol/trichloroethylene(ME/TRI). From the equilibrium swelling of PET, total and partial isotherms of PET for sorption of solvent mixtures and isotherms for distribution of the components between the phases were taken. Also the shrinkage and the crystallinity of PET treated with binary mixtures were investigated. The results obtained were summerized as follows: 1. All isotherms for distribution of the components between the phase deviated from the diagonal in system of PET-binary mixtures. Especially in the binary mixtures of ME/PER or ME/TRI, selectivo sorption of chlorinated hydrocarbon PER and TRI by PET occured. 2. The shrinkage of PET treated in binary mixrures was increased to compare with single solvent-treated, but the composition of binary mixtures corresponding to maximum values of shrinkage was not always agreed with the composition of binary mixtures corresponding to maximum values of shrinkage was not always agreed with the composition of binary mixtures exhibiting of the maximum swelling of PET. 3. The crystallinity of PET treated in binary mixtures generally increased than that of single solvent-treated.

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$\pi$-A Isotherms and Electrical Properties of Polyamic acid Alkylamine salts(PAAS) Langmuir-Blodgett Films

  • Kim, Tae-Wan;Park, Jun-Su;Cho, Jong-Sun;Kang, Dou-Yol
    • E2M - 전기 전자와 첨단 소재
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    • 제11권10호
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    • pp.60-65
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    • 1998
  • Deposition conditions, surface morphology, and electrical properties of polyamic acid alkylamine salts (PAAS) Langmuir-Blodgett(LB) films have been investigated through a study of surface pressure-area $\pi$-A isotherms, AFM (atomic force microscopy), and current-voltage characteristics. To obtain the optimum conditions of film deposition, the $\pi$-A isotherms were examined by varying temperature, barrier moving speed, dipping speed, spreading amount of solution etc. The Z-type LB films were made at the surface pressure of 5 mN m-1 and 25 mN m-1 for the AFM study; the former surface pressure forms the gas phase and the latter one forms the solid phase. The LB film made in the gas phase show domains with a size of about 200 A diameter and 70 A height. However, the LB films made in the solid phase show a very smooth surface with 2 A surface roughness. In the current-voltage characteristics measured along the perpendicular direction of the films, ohmic conduction has been observed below 105 V cm-1 and the calculated electrical conductivity is about 10-13 S cm-1. Nonohmic conduction has been observed above = 10-11 V cm and the conduction mechanism can be explained by the Schottky effect.

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