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  • Chemical Engineering  (5)
  • 1990-1994  (5)
  • 1
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The incompressible lattice-gas model by ten Brinke and Karasz is adopted to introduce the effect of specific interactions into a recently-presented Monte-Carlobased lattice expression for the Helmholtz energy of nonrandom mixing. While the lattice remains incompressible, intermolecular forces consist of two types: London dispersion forces and specific (chemical) forces. The specific interactions between similar components, as well as those between dissimilar components, are incorporated in a systematic manner. Closed-loop temperature-composition phase diagrams are obtained. The theory is compared with experimental data for several binary systems, including polymer solutions, which exhibit closed-loop coexistence curves. Theoretical and experimental results are in good agreement.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A molecular-thermodynamic model is developed for representing thermodynamic properties of aqueous two-phase systems containing polymers, electrolytes, and proteins. The model is based on McMillan-Mayer solution theory and the generalized mean-spherical approximation to account for electrostatic forces between unlike ions. The Boublik-Mansoori equation of state for hard-sphere mixtures is coupled with the osmotic virial expansion truncated after the second-virial terms to account for short-range forces between molecules.Osmotic second virial coefficients are reported from low-angle laser-light scattering (LALLS) data for binary and ternary aqueous solutions containing polymers and proteins. Ion-polymer specific-interaction coefficients are determined from osmoticpressure data for aqueous solutions containing a water-soluble polymer and an alkali chloride, phosphate or sulfate salt.When coupled with LALLS and osmotic-pressure data reported here, the model is used to predict liquid-liquid equilibria, protein partition coefficients, and electrostatic potentials between phases for both polymer-polymer and polymer-salt aqueous two-phase systems. For bovine serum albumin, lysozyme, and α-chymotrypsin, predicted partition coefficients are in excellent agreement with experiment.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1401-1409 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A thermodynamic analysis unambiguously relates interfacial-electrostatic-potential differences measured with Ag/AgCl capillary electrodes to the equilibrium properties of an aqueous two-phase system. Interfacial electrostatic potentials were measured as a function of total α-cyclodextrin concentration in an aqueous two-phase system containing 9.1 wt. % poly (ethylene glycol), 6.1 wt. % Dextran T-70, and 1-mM potassium iodide. An order-of-magnitude increase in the interfacial electrostatic potential was observed as the total concentration of α-cyclodextrin increased from 0 to 1 mM. Measured partition coefficients for α-chymotrypsin, lysozyme, and bovine serum albumin depend strongly on α-cyclodextrin concentration. For example, as the concentration of α-cyclodextrin rises from 0 to 1 mM, the partition coefficient of lysozyme decreases from 1.7 to 0.55. These measurements are in good agreement with theoretical expectations.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 215-223 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple statistical-mechanical theory, known as the random-phase approximation, is applied to study liquid-liquid phase separations in solutions of globular proteins. Phase separation may be induced by addition of nonionic polymer or/and ordinary electrolytes. In this analysis, the osmotic-attraction mechanism, whereby the depletion of “solvent” particles between two proteins causes an attractive force, is primarily responsible for phase separation. For one-component models of protein solutions, the theory yields simple algebraic expressions for the equation of state and for the chemical potential of the protein. This analytical theory describes the observed solubility behavior of proteins, including the effect of protein and polymer size, protein charge and concentration, and concentration of simple electrolytes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 676-691 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A semiempirical thermodynamic method is developed to establish a framework for calculating vapor-liquid and liquid-liquid equilibria in ternary systems containing water, an organic solvent, and a salt. Careful attention is given to precise definition of standard states. Short-range ion-solvent forces are taken into account primarily by a chemical-equilibrium method based on stepwise ion solvation; however, physical contributions also contribute. Water-cosolvent nonideality is described by an extended equation of the van Laar form. Long-range electrostatic forces between ions are taken into account by an extended Debye-Hückel equation with corrections for transferring from a McMillan-Mayer to a Lewis-Randall framework.The new method is illustrated with results for several systems including saturated aqueous mixtures of LiBr or LiCl with methanol where the salt concentration exceeds 20 molal. The method developed here is of particular interest for process calculations in extractive crystallization, a low-energy operation for producing salt from aqueous solution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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