Mohammad K. Khoshkbarchi

University of Santiago de Compostela, Santiago de Compostela, Galicia, Spain

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Publications (32)48.35 Total impact

  • Sara Lago, Héctor Rodríguez, Mohammad K. Khoshkbarchi, Ana Soto, Alberto Arce
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    ABSTRACT: With a decrease in world oil reserves and a higher demand for petroleum and its derived products, the effective exploitation of oil reservoirs has become increasingly important. Enhanced oil recovery (EOR) assisted by surfactants is an effective method for recovering the oil from reservoirs that have lost their drive after the application of primary and secondary recovery methods. This research is aimed at showing the suitability of several ionic liquids as effective replacements for conventional surfactants in EOR. The reservoir fluid has been modelled as a ternary system of water (pure water or aqueous solution of NaCl) plus the ionic liquid trihexyl(tetradecyl)phosphonium chloride plus dodecane. Determination of its liquid–liquid phase equilibrium indicates the formation of a Winsor type III system, with a triphasic region and adjacent biphasic regions. The interfacial tensions in the system corroborate the ability of the ionic liquid to act as a surface active agent, as desirable for its use in an EOR process. A relevant transport property such as viscosity, in addition to density, has been experimentally measured for the equilibrium phases.
    RSC Advances 09/2012; 2(25):9392-9397. · 3.71 Impact Factor
  • Ana Soto, Alberto Arce, Mohammad K. Khoshkbarchi
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    ABSTRACT: Room temperature ionic liquids (RTIL) are a new class of molten salts that are liquid at ambient temperature and due to their many unique properties are safe and environmentally friendly chemicals. In this study investigation has been carried out to determine the suitability of an RTIL in replacing volatile organic solvents for the liquid–liquid extraction of antibiotics from aqueous solutions. New experimental data at 298.15 K for the partitioning of two antibiotics, amoxicillin and ampicillin, between water and an RTIL, 1-methyl-3-octylimidazolium tetrafluoroborate ([OMIM][BF4]), at two pH values of 4 and 8 have been reported. The results confirm the suitability of this RTIL for the extraction of the antibiotics studied. The results also show that the partitioning of antibiotics between [OMIM][BF4] and aqueous phase is highly influenced by the pH of the solution as well as their chemical structures. The NRTL model has been employed to correlate the experimental data.
    Separation and Purification Technology. 01/2005;
  • Mohammad K. Khoshkbarchi, Juan H. Vera
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    ABSTRACT: Activity-coefficient data were measured for NaCl in the system water–NaCl–DL-valine at 25°C. The activity coefficients of DL-valine were then calculated through rigorous thermodynamic relations. The activity coefficients of the amino acids in this and other aqueous systems containing electrolytes were modeled using an expression for the excess Gibbs free energy of the solution. The model combines a contribution for long-range interactions, given either by the Bromley equation or the K-V equation, and a contribution of short-range interactions represented by a ternary NRTL or Wilson expression. The model accurately correlates the activity coefficients of ten amino acids in aqueous solutions and of six amino acids in aqueous electrolyte solutions.
    AIChE Journal 06/2004; 42(8):2354 - 2364. · 2.58 Impact Factor
  • Mohammad K. Khoshkbarchi, Juan H. Vera
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    ABSTRACT: Ion-selective electrodes were used to measure the activity coefficients at 298.2 K of individual ions in aqueous solutions of NaCl and NaBr up to of 5 molal and of KCl up to 4 molal. The mean ionic activity coefficients of NaCl, NaBr, and KCl, obtained from the values of the activity coefficients of the individual ions, show good agreement with values reported in the literature. The experimental results show that the activity coefficients are different for the anion and the cation in an aqueous solution of a single electrolyte and that, as expected from the ion-ion and ion-solvent interactions, the activity coefficient of an ion depends on the nature of its counterion. A modified form of the Pitzer's model, which distinguishes between the activity coefficients of the anion and the cation, was used to correlate the experimental results.
    AIChE Journal 06/2004; 42(1):249 - 258. · 2.58 Impact Factor
  • H. R. Radfarnia, V. Taghikhani, C. Ghotbi, M. K. Khoshkbarchi
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    ABSTRACT: The generalized quasi-chemical (GEM-QC) model proposed by Wang and Vera is modified to correlate better the phase equilibrium and to overcome the shortcoming of the original model to predict the lower critical solution temperature (LCST) of binary polymer solutions. This shortcoming is mainly because the GEM-QC model does not consider the effect of free-volume, which is important in systems containing molecules with large size differences. The proposed modification is based on replacing the combinatorial term of the GEM-QC model by a term proposed by Kontogerogis et al., which includes the effect of the free-volume. The main advantage of the free volume generalized quasi-chemical (GEM-QC-FV) model over the original GEM-QC is its ability to predict the phase behaviour of binary polymer solutions with LCST behaviour. In addition, the free volume UNIQUAC (UNIQUAC-FV) model is used to correlate VLE and LLE experimental data for binary polymer solutions. The comparison of the results obtained from the GEM-QC-FV model and the UNIQUAC-FV model shows the superiority of the GEM-QC-FV model in correlating the VLE and LLE experimental data for binary polymer solutions.
    Journal of Chemical Thermodynamics - J CHEM THERMODYN. 01/2004; 36(5):409-417.
  • Ana Soto, Alberto Arce, Mohammad K. Khoshkbarchi
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    ABSTRACT: New experimental data for the density, speed of sound, and refractive index of aqueous solutions of diglycine + NaCl and triglycine + NaCl have been reported. The apparent molar volume and apparent molar isentropic compressibility of these peptides at various NaCl concentrations have been calculated from the measured properties. The results show that both peptides exhibit a positive volume transfer to solutions with higher NaCl concentrations and a negative apparent isentropic compressibility in the presence of NaCl. These effects indicate that the apparent volumes of the peptide molecules are larger in solutions with higher NaCl concentrations and that the water molecules around the peptide molecules are less compressible than the water molecules in the bulk solvent. These effects are attributed to the doubly charged nature of the peptides and the interactions between the charged groups and hydrocarbon backbone of peptides with the ions.
    Journal of Solution Chemistry 12/2003; 33(1):11-21. · 1.13 Impact Factor
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    ABSTRACT: Electrochemical cells with two ion-selective electrodes, a cation ion-selective electrode against an anion ion-selective electrode, were used to measure the activity coefficient of amino acids in aqueous electrolyte solutions. Activity coefficient data were measured for (H2O + NaBr + glycine) and (H2O + NaBr + l-valine) at T=298.15 K. The maximum concentrations of sodium bromide, glycine, and l-valine were (1.0, 2.4, and 0.4) mol · kg−1, respectively. The results show that the presence of an electrolyte and the nature of both the cation and the anion of the electrolyte have significant effects on the activity coefficients of amino acid in aqueous electrolyte solutions.
    The Journal of Chemical Thermodynamics 01/2003; 35(9):1553-1565. · 2.30 Impact Factor
  • Héctor Rodríguez, Ana Soto, Alberto Arce, Mohammad K. Khoshkbarchi
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    ABSTRACT: New experimental data at 25C for the density, velocity of sound, refractive index, and viscosity of aqueous solutions of DL-alanine and NaCl are reported. The apparent molar volume and isentropic compressibility of DL-alanine in aqueous electrolyte solutions have been calculated from the measured properties. The results show that DL-alanine exhibits a positive volume transfer to solutions of a higher NaCl concentration and a negative apparent isentropic compressibility for DL-alanine in the presence of NaCl. These effects indicate that the apparent volume of DL-alanine is larger in solutions with higher electrolyte concentration and the water molecules surrounding the DL-alanine molecules are less compressible than the water molecules in the bulk solution. The results also show an increase in the viscosity of the solution with an increase in both DL-alanine and NaCl concentrations. These effects are attributed to the two charged groups of DL-alanine and the interactions between the charged groups and the hydrocarbon backbone of DL-alanine with the ions. A model, consisting of a short-range interaction term represented by a virial expansion and a Debye-Hckel term that considers long-range interactions, has been developed to correlate the measured experimental data.
    Journal of Solution Chemistry 12/2002; 32(1):53-63. · 1.13 Impact Factor
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    ABSTRACT: The activity coefficient data were reported for (water + potassium chloride +dl -valine) at T= 298.15 K and (water + sodium chloride +l -valine) at T= 308.15 K. The measurements were performed in an electrochemical cell using ion-selective electrodes. The maximum concentrations of the electrolytes and the amino acids studied were 1.0 molality and 0.4 molality, respectively. The results of the activity coefficients of dl -valine are compared with the activity coefficients of dl -valine in (water + sodium chloride +dl -valine) system obtained from the previous study. The results show that the presence of an electrolyte and the nature of its cation have a significant effect on the activity coefficient of dl -valine in aqueous electrolyte solutions.
    Journal of Chemical Thermodynamics - J CHEM THERMODYN. 01/2002; 34(8):1297-1309.
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    ABSTRACT: Liquid−liquid equilibria of water + propionic acid + methyl butyl ketone (2-hexanone) and of water + propionic acid + methyl isopropyl ketone (3-methyl-2-butanone) systems were measured at the temperatures (25, 35, and 45) °C. Complete phase diagrams were obtained by determining solubility and the tie-line data. The reliability of the experimental tie-line data was determined through the Othmer−Tobias plots. Distribution coefficients and separation factors were evaluated over the immiscibility regions. It is concluded that both methyl butyl ketone and methyl isopropyl ketone are suitable separating agents for dilute aqueous propionic acid.
    Journal of Chemical and Engineering Data - J CHEM ENG DATA. 07/2001; 46(5).
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    ABSTRACT: Electrochemical cells with two ion-selective electrodes against a single-junction reference electrode were used to obtain the activity coefficients of glycine in aqueous electrolyte solutions. Activity coefficient data were presented for {H2O + KCl (mS) + glycine (mA)}, and {H2O + NaCl (mS) + glycine (mA)} atT = 298.15 K and T = 308.15 K, respectively. The results show that the presence of an electrolyte and the nature of its cation have a significant effect on the activity coefficient of glycine in aqueous electrolyte solutions and, in turn, on the method of separation from its culture media. The results of the mean ionic activity coefficients of KCl were compared with those values reported in the literature, which were obtained by the isopiestic method. It was found that the method applied in this study provides accurate activity coefficient data. The effect of temperature on the mean ionic activity coefficient of NaCl in presence of glycine was also investigated.
    The Journal of Chemical Thermodynamics 07/2001; 33(7):821–836. · 2.30 Impact Factor
  • Vahid Taghikhani, Hamid Modarress, Mohammad K Khoshkbarchi, Juan H Vera
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    ABSTRACT: The mean spherical approximation (MSA) has been applied to accurately correlate the activity coefficients of individual ions in aqueous solutions of single 1:1 electrolytes. The size parameters of the ions are considered to be composition-dependent in order to account for changes in the hydration of the ions. The values of the size parameters show that the hydration of the ions decreases as the electrolyte concentration increases. The dehydration of a particular ion depends on the nature of its counterion. The results obtained from the full MSA and from a simplified version of MSA (SMSA), are compared. The use of the simplified version has small effect on the final results and dramatically reduces the computational effort. The results obtained from the MSA compare favorably with those of the Bates' and the Pitzer's models.
    Fluid Phase Equilibria 01/2000; 167(2):161-171. · 2.38 Impact Factor
  • A Soto, A Arce, M K Khoshkbarchi
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    ABSTRACT: Experiments at 298.15 K have been performed to measure the density, velocity of sound and refractive index in three water+glycine+electrolyte systems. The electrolytes studied were KCl, KNO3 and NaNO3. The values of apparent molar volume and isentropic compressibility of glycine in aqueous electrolyte solutions were calculated from the measured data. The results obtained in this study and those reported previously for water+glycine+NaCl system have been comparatively studied. The results show that the nature of both the cation and the anion of an electrolyte influence the behaviour of glycine in aqueous solutions. For all four electrolytes studied, the comparison shows a positive volume transfer for glycine from an electrolyte solution to a more concentrated solution of the same electrolyte. The results also show a negative apparent isentropic compressibility for glycine in the presence of the electrolytes studied. These effects indicate that the volume of a glycine molecule is larger in solutions with higher electrolyte concentration and the water molecules around the glycine molecules are less compressible than the water molecules in the bulk solution. These effects were attributed to the doubly charged behaviour of glycine and to the formation of physically bonded ion-pairs between the charged groups of glycine and the cation and the anion of the electrolyte.
    Biophysical Chemistry 02/1999; 76(1):73-82. · 2.28 Impact Factor
  • Ana Soto, Alberto Arce, Mohammad K. Khoshkbarchi, Juan H Vera
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    ABSTRACT: Measurements were performed to determine the solubilities at 298.2 K of two pairs of amino acids in aqueous solutions. The systems studied were water+glycine+dl-aspartic acid and water+glycine+dl-phenylalanine. The results show that for these systems the solubility of an amino acid increases as the concentration of the other amino acid increases. The solubility of dl-phenylalanine passes through a maximum with an increase in the glycine concentration. Comparison of the results obtained in this work with those reported in previous studies, indicates that the solubility of an amino acid in the presence of another amino acid depends not only on the concentration of the second amino acid, but also on the chemical structure of both amino acids. A model has been developed to correlate the solubilities of an amino acid in aqueous solutions of another amino acid. The activity coefficients of the amino acids, required to correlate the solubility were represented by two different models. An NRTL and a perturbed hard sphere model, with two amino acid–amino acid adjustable interaction parameters, were used. The water–amino acid interaction parameters in the NRTL model for the amino acids with low solubilities, namely dl-aspartic acid and dl-phenylalanine, were set to zero. Both activity models can accurately correlate the solubility of an amino acid in aqueous solutions of another amino acid. It was found that, at amino acid concentrations higher than the saturation in pure water, the NRTL model can extrapolate the activity coefficients of amino acids better than the perturbed hard sphere model.
    Fluid Phase Equilibria 01/1999; 158(1):893-901. · 2.38 Impact Factor
  • Ana Soto, Alberto Arce, Mohammad K Khoshkbarchi
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    ABSTRACT: Experiments have been performed at 298.15 K to measure the density, sound velocity and refractive index of glycine in aqueous solutions of NaCl over a wide range of both glycine and NaCl concentrations. The values of apparent molar volume and isentropic compressibility of glycine were calculated from the measured data. The results show a positive transfer volume of glycine from an NaCl solution to a more concentrated NaCl solution. This indicates that the size of a glycine molecule is larger in a solution with higher NaCl concentration. The negative values of apparent isentropic compressibility imply that the water molecules around the glycine molecules are less compressible than the water molecules in the bulk solution. These effects are attributed to the doubly charged behaviour of glycine and to the formation of physically bonded ion-pairs between the charged groups of glycine and sodium and chloride ions. The formation of ion-pairs, whose extents of binding reactions depend on the concentrations of both NaCl and glycine, alter the hydration number of glycine. This also explains the reason for the increase in the size of glycine with an increase in the NaCl concentration. A model based on the Pitzer formalism has been developed to correlate the activity coefficient, apparent molar volume and isentropic compressibility of glycine in aqueous solutions of NaCl. The results show that the model can accurately correlate the interactions in aqueous solutions of glycine and NaCl.
    Biophysical Chemistry 10/1998; · 2.28 Impact Factor
  • A Soto, A Arce, M K Khoshkbarchi, J H Vera
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    ABSTRACT: The solubilities at 298.2 K of dl-aminobutyric acid in aqueous solutions of NaCl, KCl, NaNO(3) and KNO(3) were measured. The solubility of DL-aminobutyric acid was found to be influenced by the concentration and by the nature of both the cation and the anion of the electrolyte. Comparison of the results obtained in this study and those for other amino acids reported in the literature, indicates that the structure of the hydrocarbon backbone of an amino acid plays an important role in the interactions of an amino acid with an electrolyte. A thermodynamic model has been used to correlate the solubilities of DL-aminobutyric acid in aqueous electrolyte solutions. The activity coefficients of the amino acid in the electrolyte solutions, were represented by a model proposed by Khoshkbarchi and Vera [M.K. Khoshkbarchi, J.H. Vera, AIChE J. 42 (1996) 2354; M.K. Khoshkbarchi, J.H. Vera, Ind. Eng. Chem. Res. 35 (1996) 4755]. This model, which considers a combination of both long- and short-range interactions, contains only two adjustable parameters. All other parameters are available in the literature. The model can accurately correlate the solubility of dl-aminobutyric acid in aqueous solutions of electrolytes.
    Biophysical Chemistry 08/1998; 73(1-2):77-83. · 2.28 Impact Factor
  • Mohammad K. Khoshkbarchi, Juan H. Vera
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    ABSTRACT: An analogical approach has been used to extend to mixtures the radial distribution function of Percus–Yevick type of equations of state for hard spheres. The proposed approach follows the same formalism employed by Mansoori et al. to extend to mixtures the Carnahan–Starling equation of state. The generality of the proposed method permits to extend to mixtures equations of state with different singularities. In this work, it is applied to an equation of state which meets the correct low density and high density limits, previously proposed by Khoshkbarchi and Vera. The results show that both the radial distribution function and the resulting equation of state for a mixture of hard spheres, developed in this study, can accurately represent the computer simulation data while satisfying the correct limit at close-packing.
    Fluid Phase Equilibria 01/1998; · 2.38 Impact Factor
  • Ana M. Soto-Campos, Mohammad K. Khoshkbarchi, Juan H. Vera
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    ABSTRACT: The effects of the nature of the cation and the anion of three electrolytes on the activity coefficient of dl-alanine in aqueous solutions at 25°C, are investigated. The electrolytes studied are NaCl, KCl and NaNO3. The study covers up to 1.6 molality dl-alanine and up to 1.0 molality electrolyte. An electrochemical cell with two ion selective electrodes, a cation and an anion ion selective electrode, versus a double junction reference electrode, was used to measure the activity coefficients of dl-alanine in aqueous electrolyte solutions. Experimental data for the activity coefficients of dl-alanine in water+KCl+dl-alanine and water–NaNO3+dl-alanine systems measured at 25°C are reported. Experimental data for the activity coefficients of dl-alanine in water+NaCl+dl-alanine system were obtained from a previous study. Measurement of activity coefficients of amino acids in aqueous electrolyte solutions: experimental data for the systems H2O+NaCl+glycine and H2O+NaCl+dl-alanine at 25°C. Ind. Eng. Chem. Res. 35, pp. 2735–2742.]. The results of the activity coefficients of dl-alanine in the presence of different 1:1 electrolytes are compared and discussed. The results show that the nature of both the cation and the anion of an electrolyte have significant effects on the activity coefficients of dl-alanine in aqueous electrolyte solutions.
    Fluid Phase Equilibria 01/1998; 142(1):193-204. · 2.38 Impact Factor
  • A M Soto-Campos, M K Khoshkbarchi, J H Vera
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    ABSTRACT: The activity coefficients at 298.15 K of glycine in water + NaNO(3) + glycine system and dl-methionine in water + NaCl + dl-methionine system are reported. The measurements were performed in an electrochemical cell with two ion selective electrodes, a cation and an anion ion selective electrode, each versus a double junction reference electrode. The concentrations of the electrolytes and the amino acids studied covered up to 1.0 molality electrolyte, 2.4 molality glycine and 0.2 molality dl-methionine. The results of the activity coefficients of glycine are compared with the activity coefficients of glycine in water + NaCl + glycine and water + KCl + glycine systems, obtained from the previous studies. The results show that the nature of both the cation and the anion of an electrolyte have significant effects on the activity coefficient of glycine in aqueous electrolyte solutions. The results also show that there are attractive interactions between the molecules of glycine and NaNO(3) and repulsive interactions between the molecules of dl-methionine and NaCl.
    Biophysical Chemistry 10/1997; 67(1-3):97-105. · 2.28 Impact Factor
  • Mohammad K. Khoshkbarchi, Ana M. Soto-Campos, Juan H. Vera
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    ABSTRACT: The activity coefficients at 25‡C of DL-serine and L-serine in aqueous solutions of NaCl and KC1 were measured. This study examines the effect of the nature of the cation of the electrolyte on the activity coefficients of the optical-isomers of serine in aqueous solutions for molality of serine up to 0.4 and molality of electrolyte up to 1. An electrochemical cell with two ion-selective electrodes, a cation, and an anion ion selective electrode,vs. a double-junction reference electrode was used to measure the activity coefficients of the electrolyte and the results were converted to the activity coefficients of serine in the aqueous electrolyte solution. The comparison of the results obtained for DL- and L-serine indicates that the two optical isomers have identical interactions with electrolytes in aqueous solutions and that for this amino acid the effect of the cation of the electrolyte is not significant. Comparison of these results with previous measurements for DL-alanine in aqueous solutions of the same electrolytes show the notable effect of the backbone of the amino acid.
    Journal of Solution Chemistry 09/1997; 26(10):941-955. · 1.13 Impact Factor

Publication Stats

193 Citations
48.35 Total Impact Points

Institutions

  • 1997–2005
    • University of Santiago de Compostela
      • Departamento de Ingeniería Química
      Santiago de Compostela, Galicia, Spain
  • 2004
    • Sharif University of Technology
      • Department of Chemical and Petroleum Engineering
      Tehrān, Ostan-e Tehran, Iran
  • 1995–2004
    • McGill University
      • Department of Chemical Engineering
      Montréal, Quebec, Canada
  • 1996
    • Universidad de Valladolid
      Valladolid, Castille and León, Spain