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Prediction of Thermodynamic Parameters in Solutions with Similar Composition to Plasma or Blood

Sadeghi, Masoud | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 44283 (06)
  4. University: Sharif University of Technology
  5. Department: chemical and petroleum engineering
  6. Advisor(s): Abdekhodaie, Mohammad Jafar; Ghotbi, Cyrus
  7. Abstract:
  8. Serum osmolality is an important physiological quantity that is directly related to health condition of human body. Glucose, urea, and NaCl are the main components which determine the value of serum osmolality. Besides, calcium and potassium are vital inorganic cations for the body. Thus, it is of high importance to investigate the interactions between these physiological solutes in aqueous solution. Thermodynamic quantities like osmotic and activity coefficients contain enthalpic and entropic information and thus are a direct measure of interactions in these complex systems. Thus, theoretical and experimental methods were applied to investigate these thermodynamic parameters in multi-solute aqueous solutions containing vital components for alive bodies.
    In the first step, the mean spherical approximation (MSA) model, coupled with two hard sphere models, was used to predict the activity coefficients of mixtures of electrolyte solutions at different temperatures and concentrations. The models, namely Ghotbi-Vera-MSA (GV-MSA) and Mansoori et al.-MSA (BMCSL-MSA), were directly used without introducing any new adjustable parameters for mixtures of electrolyte solutions. The results showed that the studied models predict accurately the activity coefficients for single electrolyte aqueous solutions at different temperatures. In the systems of binary aqueous electrolyte solutions with a common anion, the GV-MSA model has slightly better accuracy in predicting the activity coefficients. Also, it was observed that the GV-MSA model can more accurately predict the activity coefficients for ternary electrolyte solutions with a common anion, especially at higher concentrations.
    In second step, osmotic coefficients were measured and modeled in aqueous solutions of urea and different salts. These data were obtained at 310.15 K by using the vapor-pressure osmometry. Ternary aqueous urea solutions containing NaCl, KCl, NaBr, KBr, LiBr, NaNO3, and LiNO3 at two different concentrations of urea (0.3 and 1 molal) as well as at three salt concentrations (0.25, 0.5, and 0.75 molal) were considered. Experimental data obtained in this work showed that the solute with higher concentration determines the behavior of osmotic coefficients in these solutions. Also, ion-specific effects were observed in these systems. The ePC-SAFT model (without any adjustable mixture parameter) was used to accurately predict the experimental osmotic coefficients of the studied mixtures.
    In the final step, cryoscopic osmometer was used to measure the osmotic coefficient in ternary NaCl or KCl or CaCl2/urea or glucose/ water and quaternary NaCl/urea/glucose/water systems at physiologically relevant concentrations. The results showed that NaCl determines the osmotic coefficients in the urea/glucose/water/NaCl system. At physiologically important solute concentrations the value was found to be ~0.93.
    Finally, the ePC-SAFT equation of state was applied to model these biological systems. Therefore, a modeling strategy for glucose was used in a first step. Applying appropriate mixing rules allows for quantitatively predicting properties of multi-solute aqueous solutions
  9. Keywords:
  10. Electrolyte Solution ; Activity Coefficient ; Osmotic Coefficient ; Complex System ; Salt-Biomolecule Interaction ; ePC-SAFT Model

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