• Title, Summary, Keyword: Thermodynamic parameters

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Solubility of celecoxib in N-methyl-2-pyrrolidone + water mixtures at various temperatures: Experimental data and thermodynamic analysis

  • Nozohouri, Sarah;Shayanfar, Ali;Cardenas, Zaira Johanna;Martinez, Fleming;Jouyban, Abolghasem
    • The Korean Journal of Chemical Engineering
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    • v.34 no.5
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    • pp.1435-1443
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    • 2017
  • Solubility is one of the most significant physicochemical properties of drugs, and improving the solubility of drugs is still a challenging subject in pharmaceutical sciences due to requirements of enhancing their bioavailability. Celecoxib, according to the biopharmaceutics classification system (BCS), is a class 2 drug, possessing low water solubility (<$5{\mu}g{\cdot}mL^{-1}$) and high permeability. Increasing the solubility of this group can lead to improved bioavailability, dose reduction and subsequently, increased efficiency and reduced side effects. In this study, celecoxib solubility was determined in binary mixtures of N-methyl-2-pyrrolidone (NMP)+water at 293.2, 298.2, 303.2, 308.2 and 313.2 K. The solubility of celecoxib is increased with the addition of NMP to the aqueous solutions and reaches a maximum value in neat NMP. In addition, increased temperature leads to enhanced solubility of celecoxib in a given solvent composition. The solubility data of celecoxib in NMP+water at different temperatures were correlated using different mathematical models including, the Jouyban-Acree model and a combination of the Jouyban-Acree and van't Hoff models. Thermodynamic parameters, Gibbs energy, enthalpy and entropy of dissolution processes were performed based on Gibbs and van't Hoff equations. Thermodynamic analysis allowed observing two main entropy or enthalpy-driven dissolution mechanisms, varying according to the composition of aqueous mixtures. Moreover, preferential solvation of celecoxib by water is observed in water-rich mixtures but preferential solvation by NMP was seen in mixtures with similar composition and also in NMP-rich mixtures.

Kinetic and Thermodynamic Studies of Brilliant Green Adsorption onto Carbon/Iron Oxide Nanocomposite (탄소/산화철 나노복합재료의 Brilliant Green 흡착에 대한 반응속도론적, 열역학적 연구)

  • Ahmad, Rais;Kumar, Rajeev
    • Journal of the Korean Chemical Society
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    • v.54 no.1
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    • pp.125-130
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    • 2010
  • In the present work, we have investigated the adsorption efficiency of carbon/iron oxide nanocomposite towards removal of hazardous brilliant green (BG) from aqueous solutions. Carbon/iron oxide nanocomposite was prepared by chemical precipitation and thermal treatment of carbon with ferric nitrate at $750^{\circ}C$. The resulting material was thoroughly characterized by TEM, XRD and TGA. The adsorption studies of BG onto nanocomposite were performed using kinetic and thermodynamic parameters. The adsorption kinetics shows that pseudo-second-order rate equation was fitted better than pseudo-first-order rate equation. The experimental data were analyzed by the Langmuir and Freundlich adsorption isotherms. Equilibrium data was fitted well to the Langmuir model with maximum monolayer adsorption capacity of 64.1 mg/g. The thermodynamic parameters were also deduced for the adsorption of BG onto nanocomposite and the adsorption was found to be spontaneous and endothermic.

Spectroscopic investigations on the interaction of bovine serum albumin with amoxicillin and cloxacillin

  • BHALCHANDRA P. KAMAT,
    • Journal of Photoscience
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    • v.12 no.1
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    • pp.11-15
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    • 2005
  • The mechanism of interaction of two drugs viz., amoxicillin and cloxacillin with bovine serum albumin has been investigated using fluorescence absorption and circular dichroism spectroscopy. The quenching mechanism of fluorescence of bovine serum albumin by amoxicillin and cloxacillin was discussed. The binding sites number n and apparent binding constant Kwere measured by fluorescence quenching method. The thermodynamic parameters obtained from data at different temperatures were calculated. The distance r between donor (bovine serum albumin) and acceptor (amoxicillin and cloxacillin) was obtained according to Forster theory of non-radiative energy transfer. The effect of common ions on binding constant was also investigated. The results of synchronous fluorescence spectra, UV-vis absorption spectra and circular dichroism of BSA in presence of amoxicillin and cloxacillin show that the conformation of bovine serum albumin changed

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Binding of Acid Dyes by Crosslinked Poly(4-vinylpyridine) in Ethylene Glycol (에틸렌글리콜중에서 가교폴리(4-비닐피리딘)과 산성염료와의 결합)

  • Lee, Suk Kee;Kim, Woo Sik
    • Textile Coloration and Finishing
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    • v.9 no.3
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    • pp.27-32
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    • 1997
  • Two poly(4-vinylpyridines) having different degree of crosslinking were prepared by radical copolymerization of 4-vinylpyridine with N, N'-tetramethylenebis-acrylamide as a crosslinker. The abilities of these crosslinked polymers to bind acid dyes (methyl orange, ethyl orange, and propyl orange) were investigated at various temperatures in ethylene glycol as the binding medium. From the equilibrium amounts, the first binding constants and thermodynamic parameters for the bindings were evaluated. The first binding constants and thermodynamic parameters were not varied with these dyes. This result indicates that there is no hydrophobic interaction between the crosslinked polymers and the dyes in ethylene glycol. However, the first binding constants showed bell-shaped curves againtst the binding temperatures. This result could be explained in terms of the crosslinked hole size with temperature variation.

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Approximate Nonrandom Two-Fluid Lattice-Hole Theory. Thermodynamic Properties of Real Mixtures

  • 유기풍;신훈용;이철수
    • Bulletin of the Korean Chemical Society
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    • v.18 no.8
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    • pp.841-850
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    • 1997
  • A simple molecular theory of mixtures is formulated based on the nonrandom two-fluid lattice-hole theory of fluids. The model is applicable to mixtures over a density range from zero to liquid density. Pure fluids can be completely characterized with only two molecular parameters and an additional binary interaction energy is required for a binary mixture. The thermodynamic properties of ternary and higher order mixtures are completely defined in terms of the pure fluid parameters and the binary interaction energies. The Quantitative prediction of vapor-liquid, and solid-vapor equilibria of various mixtures are demonstrated. The model is useful, in particular, for mixtures whose molecules differ greatly in size. For real mixtures, satisfactory agreements are resulted from experiment. Also, the equation of state (EOS) is characterized well, even the liquid-liquid equilibria behaviors of organic mixtures and polymer solutions with a temperature-dependent binary interaction energy parameter.

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A Study on the Polymerization of Energetic Poly(NEO) (에너지를 함유한 선 폴리머인 poly(NEO) 제조 공정 연구)

  • Cheun Young Gu;Kim Jin Seuk
    • Journal of the Korea Institute of Military Science and Technology
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    • v.7 no.2
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    • pp.109-117
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    • 2004
  • We synthesized energetic prepolymer(2-nitrato ethyl oxirane, NEO) for plastic-bonded explosive and measured its thermodynamic parameters. 2-Nitrato ethyl oxirane(NEO) as a monomer was synthesized from 4-butene-ol, the first-step was preparation of 1-nitrate-3-butene and second-step was synthesized 2-nitrate-ethyl oxirane from 1nitrate-3-butene and then polymerized by cationic ring opening polymerization. The unreacted monomer concentration was measured by GC. The thermodynamic parameters were obtained from the ceiling temperature(Tc) values of 1 mole monomer at each reaction temperature. We varied feed rate of monomer, concentration of initiator and monomer to control molecular weight and polydispersity of perpolymer(NEO). Number average molecular weight(Mn), polydispersity(PD), and glass transition temperature(Tg), viscosity of prepolymer(NEO) were 2000, 1.07, $-55^{\circ}C$ and 300 poise respectively.

Solvent Extraction of Zinc from Strong Hydrochloric Acid Solution with Alamine336

  • Lee, Man-Seung;Nam, Sang-Ho
    • Bulletin of the Korean Chemical Society
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    • v.30 no.7
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    • pp.1526-1530
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    • 2009
  • Solvent extraction reaction of Zn(II) by Alamine336 from strong HCl solution up to 10 M was identified by analyzing the data reported in the literature. The equilibrium constant of this reaction was estimated by considering the complex formation between zinc and chloride ion. The necessary thermodynamic parameters, such as equilibrium constant for the formation of complexes and the interaction parameters, were evaluated from the thermodynamic data reported in the literature. The following solvent extraction reaction and the equilibrium constant was obtained by considering the activity coefficients of solutes present in the aqueous phase with Bromley equation. $Zn^{2+}\;2Cl^{-}\;+\;R_3NHCl_{org}\;=\;ZnCl_3R_3NH_{org},\;K_{ex}\;=\;6.33\;{\times}\;10^2$ There was a good agreement between measured and calculated distribution coefficients of Zn(II).

Thermodynamic Performance Characteristics of Organic Rankine Cycle (ORC) using LNG Cold Energy (LNG 냉열을 이용하는 유기랭킨사이클(ORC)의 열역학적 성능 특성)

  • Kim, Kyoung Hoon;Ha, Jong Man;Kim, Kyung Chun
    • Journal of the Korean Institute of Gas
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    • v.18 no.2
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    • pp.41-47
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    • 2014
  • In this work a thermodynamic performance analysis is carried out for a combined cycle consisted of an organic Rankine cycle (ORC) and a LNG cycle. The combined system uses a low grade waste heat in the form of sensible energy and the LNG cold energy is used for power generation as well as for heat sink. The effects of the key parameters of th system such as turbine inlet pressure, condensation temperature and source temperature on the characteristics of system are throughly investigated. The simulation results show that the thermodynamic performance of the combined system can be significantly improved compared to the normal ORC which is not using the LNG cold energy.

Performance Characteristics of a Combined Regenerative Ammonia-Water Based Power Generation Cycle Using LNG Cold Energy (LNG 냉열을 이용하는 암모니아-물 복합 재생 동력 사이클의 성능 특성)

  • Kim, Kyounghoon;Oh, Jaehyeong;Jeong, Youngguan
    • Transactions of the Korean hydrogen and new energy society
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    • v.24 no.6
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    • pp.510-517
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    • 2013
  • The ammonia-water based power generation cycle utilizing liquefied natural gas (LNG) as its heat sink has attracted much attention, since the ammonia-water cycle has many thermodynamic advantages in conversion of low-grade heat source in the form of sensible energy and LNG has a great cold energy. In this paper, we carry out thermodynamic performance analysis of a combined power generation cycle which is consisted of an ammonia-water regenerative Rankine cycle and LNG power generation cycle. LNG is able to condense the ammonia-water mixture at a very low condensing temperature in a heat exchanger, which leads to an increased power output. Based on the thermodynamic models, the effects of the key parameters such as source temperature, ammonia concentration and turbine inlet pressure on the characteristics of system are throughly investigated. The results show that the thermodynamic performance of the ammonia-water power generation cycle can be improved by the LNG cold energy and there exist an optimum ammonia concentration to reach the maximum system net work production.