• Title/Summary/Keyword: Gibbs′ free energy

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Effect of NaCl, n-Butanol, and Temperature on the Micellization of Ammonium Cationic Surfactants (DTAB, TTAB, and CTAB) in Aniline Solution (아닐린 수용액에서 암모늄형 양이온성계면활성제 (DTAB, TTAB, 및 CTAB)의 미셀화에 미치는 염, n-부탄올 및 온도의 효과)

  • Lee, Dong-Cheol;Lee, Byung-Hwan
    • Journal of the Korean Applied Science and Technology
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    • v.36 no.2
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    • pp.407-416
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    • 2019
  • The criticical micelle concentration (CMC) was measured by using the UV-Vis method for the micellization of the ammonium type cationic surfactants (DTAB, TTAB, and CTAB) in the aqueous aniline solution. The enthalpy change (${\Delta}H^0$) and entropy change (${\Delta}S^0$) were calculated from the dependence of Gibbs free energy change (${\Delta}G^0$) on the temperature for micellization of the cationic surfactants between 290K and 314K. The effects of n-butanol and sodium chloride on the micellization of cationic surfactants were measured and compared with the other thermodynamic functions. All the free energy changes (${\Delta}G^0$) of the micellization were negative, all the enthalpy change (${\Delta}H^0$) were negative, and all the entropy change (${\Delta}S^0$) were positive values, respectively. The micelle formation of cationic surfactant in aniline solution is a spontaneous exothermic reaction, and the iso-structural temperature calculated from the thermodynamic values show that enthalpy and entropy contribution to the micellization are almost the same for the micellization of cationic surfactants

Partial Miscibilities in Binary Solutions with Two Kinds of Specific Interactions (두 종류의 특정상호작용을 갖는 이성분 용액의 부분 혼합도)

  • Jung, Hae-Young
    • Journal of the Korean Chemical Society
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    • v.60 no.2
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    • pp.111-117
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    • 2016
  • In this article, new Gibbs free energy of mixing is derived when there are specific interactions between solvent-solute molecules and between solute-solute molecules in binary solutions. It is asssumed that a probability of specific interactions satisfies a binomial distribution. Using this Gibbs free energy of mixing, we investigate possible types of partial miscibilities and show that Ω-shaped temperature-composition phase diagrams can exist. We calculate Ω-shaped temperature-composition phase diagram of water-2-butanol system and compare that with result calculated by the method of Hino5 et al. and the experimental data.

Solvent Effect on Relative Gibbs Free Energy and Structural Property of $Eu^{3+}\;to\;Yb^{3+}$ Ion Mutation: A Monte Carlo Simulation Study

  • Kim, Hak Seong
    • Bulletin of the Korean Chemical Society
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    • v.22 no.8
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    • pp.877-882
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    • 2001
  • The solvent effects on the relative free energies of Eu3+ to Yb3+ ion mutation in solution have been investigated using a Monte Carlo simulation of statistical perturbation theory (SPT). Our results agree well with available data that were obtained by others. Particularly, the results of water (SPC/E) solvent are almost identical with experimental data. For the present Eu3+ and Yb3+ ions, the relative free energies of solvation vs. Born’s function of bulk solvents decrease with increasing Born’s function of bulk solvents. There is also good agreement between the calculated structural properties in this study and the published works obtained by computer simulation and experimental work.

Adsorption Equilibrium, Kinetics and Thermodynamic Parameters Studies of Bismarck Brown R Dye Adsorption on Granular Activated Carbon (입상 활성탄에 대한 비스마르크 브라운 R 염료의 흡착평형, 동력학 및 열역학 파라미터에 관한 연구)

  • Lee, Jong-Jib
    • Applied Chemistry for Engineering
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    • v.24 no.3
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    • pp.327-332
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    • 2013
  • Batch experiments were carried out for adsorption equilibrium, kinetics and thermodynamic parameters of the brilliant brown R onto granular activated carbon. The operating variables studied were the initial dye concentration, contact time and temperature. Experimental equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption isotherm by linear regression method. The equilibrium process was well described by Freundlich isotherm model and from the determined separation factor (1/n), granular activated carbon could be employed as an effective treatment for the removal of bismarck brown R. From kinetic experiments, the adsorption processes were found to confirm the pseudo second order model with a good correlation and the adsorption rate constant ($k_2$) increased with increasing adsorption temperature. Thermodynamic parameters like the activation energy, change of Gibbs free energy, enthalpy, and entropy were also calculated to predict the nature of adsorption in the temperature range of 298~318 K. The activation energy was determined as 8.73 kJ/mol for 100 mg/L. It was found that the adsorption of bismarck brown R on the granular activated carbon was physical process. The negative Gibbs free energy change (${\Delta}G$ = -2.59~-4.92 kJ/mol) and the positive enthalpy change (${\Delta}H$ = +26.34 kJ/mol) are indicative of the spontaneous and endothermic nature of the adsorption process.

Hydrogen Production by Pyrolysis of Natural Gas : Thermodynamic Analysis (천연가스 열분해에 의한 수소 생산 : 열역학적 해석)

  • Yoon, Y.H.;Park, N.K.;Chang, W.C.;Lee, T.J.;Hur, T.;Lee, B.G.;Baek, Y.S.
    • Transactions of the Korean hydrogen and new energy society
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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.

Study on Adsorption Equilibrium, Kinetic and Thermodynamic Parameters of Murexide by Activated Carbon (입상 활성탄에 의한 Murexide의 흡착 평형, 동력학 및 열역학 파라미터에 관한 연구)

  • Lee, Jong-Jib
    • Clean Technology
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    • v.25 no.1
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    • pp.56-62
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    • 2019
  • The equilibrium, kinetic and thermodynamic parameters of adsorption of murexide by granular activated carbon were investigated. The experiment was carried out by batch experiment with the variables of the amount of the adsorbent, the initial concentration of the dye, the contact time and the temperature. The isothermal adsorption equilibrium was best applied to the Freundlich equation in the range of 293 ~ 313 K. From the separation factor (${\beta}$) of Freundlich equation, it was found that adsorption of murexide by granular activated carbon could be the appropriate treatment method. The adsorption energy (E) obtained from the Dubinin- Radushkevich equation shows that the adsorption process is a physical adsorption process. From the kinetic analysis of the adsorption process, pseudo second order model is more consistent than pseudo first order model. It was found that the adsorption process proceeded to a spontaneous process and an endothermic process through Gibbs free energy change ($-0.1096{\sim}-10.5348kJ\;mol^{-1}$) and enthalpy change ($+151.29kJ\;mol^{-1}$). In addition, since the Gibbs free energy change decreased with increasing temperature, adsorption reaction of murexide by granular activated carbon increased spontaneously with increasing temperature. The entropy change ($147.62J\;mol^{-1}\;K^{-1}$) represented the increasing of randomness at the solid-solution interface during the adsorption reaction of murexide by activated carbon.

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

  • Song, D.M.;Park, C.N.;Choi, J.
    • Transactions of the Korean hydrogen and new energy society
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    • v.16 no.3
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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.

A Study on Real-time Data Acquisition System and Denoising for Energy Saving Device (에너지 절약 장치용 실시간 데이터 획득 시스템 구현과 잡음제거에 관한 연구)

  • Huh, Keol;Choi, Yong-Kil;Jeong, Won-Kyo;Hoang, Chan-Ku
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.05b
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    • pp.47-53
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    • 2004
  • The paper shows that the combination of the hardware, NI PCI 6110E board and the software, Fourier and continuous wavelet transform(CWT) can be used to implement for extracting the important features of the real-time signal. The results confirmed that CWT produces the fast computation enough for the application of the real-time signal processing except the negligible time delay. In denoising case, because of the lack of translation invariance of wavelet basis, traditional wavelet thresholding leads to pseudo-Gibbs phenomena in the vicinity of discontinuities of signal. In this paper, in order to reduce the pseudo-Gibbs phenomena, wavelet coefficients are threshold and reconstruction algorithm is implement through shift-invariant gibbs free denoising algorithm based on wavelet transform footprint. The proposed algorithm can potentially be extended to more general signals like piecewise smooth signals and represents an effective solution to problems like signal denoising.

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Combustion Analysis Program of Liquid Propellant Rocket Engine (액체추진제 로켓엔진의 연소해석 프로그램)

  • Jung, Tae-Kyu
    • Aerospace Engineering and Technology
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    • v.7 no.2
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    • pp.157-161
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    • 2008
  • This study introduce a newly developed program to calculate the combustion process of combustion chamber and gas generator of liquid rocket engine by use of Gibbs free energy minimization method based on chemical equilibrium. The simulation results of the new program and CEA code of NASA were compared and showed good agreement, thus proving the validity of the newly developed in-house program for combustion analysis.

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Transformation of the enthalpy and the entropy in BSCCO:2212-2223 (BSCCO:2212-2223 박막의 엔탈피와 엔트로피 변화)

  • Cheon, Min-Woo;Park, No-Bong;Park, Yong-Pil
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.07a
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    • pp.589-590
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    • 2005
  • BSCCO:2212-2223 thin films were fabricated by using the ion beam sputter with a evaporation method at various substrate temperatures, $T_{sub}$, and ozone gas pressures, $pO_3$. The correlation diagrams of the BSCCO phases with Tsub and $pO_3$ are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 as well as Bi2212 phases come out as stable phases depending on Tsub and $pO_3$. From these results, the thermodynamic evaluation of ${\Delta}H$ and ${\Delta}S$, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase, was performed.

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