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    A new hydration model in correlating the mean ionic activity coefficient and density of aqueous electrolyte solutions

    , Article Journal of Dispersion Science and Technology ; Volume 31, Issue 5 , 2010 , Pages 641-649 ; 01932691 (ISSN) Pazuki, G. R ; Taghikhani, V ; Vossoughi, M ; Sharif University of Technology
    Abstract
    In this article, a new hydration model has been proposed to study the phase behavior of aqueous electrolyte solutions. The proposed model distinguishes between an anion and cation in the electrolyte solution. The model has three adjustable parameters which can be obtained using the experimental data of the mean ionic activity coefficients for 113 electrolyte solutions. The results of the proposed model were compared with those of obtained from the Pitzer, the E-NRTL and the E-Wilson models. The results showed that the proposed model can accurately correlate the mean ionic activity coefficients of the aqueous electrolyte solutions than the other models. Also, the proposed model was used in... 

    Activity coefficient prediction for binary and ternary aqueous electrolyte solutions at different temperatures and concentrations

    , Article Journal of Solution Chemistry ; Volume 41, Issue 1 , 2012 , Pages 75-88 ; 00959782 (ISSN) Sadeghi, M ; Ghotbi, C ; Abdekhodaie, M. J ; Sharif University of Technology
    Abstract
    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 the Ghotbi-Vera-MSA (GV-MSA) and Mansoori et al.-MSA (BMCSL-MSA), were directly used without introducing any new adjustable parameters for mixing of electrolyte solutions. In the correlation step, the anion diameters were considered to be constant, whereas the cation diameters were considered to be concentration dependent. The adjustable parameters were determined by fitting the models to the experimental mean ionic activity coefficients for single aqueous... 

    A new gibbs energy model for obtaining thermophysical properties of aqueous electrolyte solutions

    , Article Journal of Solution Chemistry ; Volume 38, Issue 2 , 2009 , Pages 171-186 ; 00959782 (ISSN) Khederlou, K ; Pazuki, G. R ; Taghikhani, V ; Vossoughi, M ; Ghotbi, C ; Sharif University of Technology
    2009
    Abstract
    In this paper, a new Gibbs energy model is proposed to study the thermophysical properties of aqueous electrolyte solutions at various temperatures. The proposed model assumes that the electrolytes completely dissociate in solution. The model also has two temperature-independent adjustable parameters that were regressed using experimental values of the mean ionic activity coefficients (MIAC) for 87 electrolyte solutions at 298.15 K. Results from the proposed model for the MIAC were compared with those obtained from the E-Wilson, E-NRTL, Pitzer and the E-UNIQUAC models, and the adjustable model parameters were used directly to predict the osmotic coefficients at this temperature. The results... 

    Prediction of hydrate formation for the systems containing single and mixed electrolyte solutions

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 26, Issue 1 , 2007 , Pages 35-45 ; 10219986 (ISSN) Shabani, M. M ; Rashtchian, D ; Ghotbi, C ; Taghikhani, V ; Khayat, G ; Sharif University of Technology
    Iranian Journal of Chemistry and Chemical Engineering  2007
    Abstract
    In this work the effect of electrolytes on hydrate formation was investigated. To do so, a new model was used in predicting the hydrate formation conditions in presence of both single and mixed electrolyte solutions. The new model is based on the van der Waals - Platteeuw hydrate equation of state. In order to evaluate the values for the activity of water in electrolyte solutions the simplified version of the Ghotbi-Vera Mean Spherical Approximation (SGV-MSA) model was used. According to the SGV-MSA model the ions in the solutions are considered as charged hard spheres with different sizes. The values of the parameters for the SGV-MSA model are independent of temperature and depend only on... 

    Extension of the dense system equation of state to electrolyte solutions

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 26, Issue 1 , 2007 , Pages 17-33 ; 10219986 (ISSN) Parsafar, G ; Panahi, A ; Sharif University of Technology
    2007
    Abstract
    In this work we have applied the Dense System Equation of State (DSEOS) to electrolyte solutions. We have found that this equation of state can predict the density of electrolyte solutions very accurately. It has been tested for different electrolytes solutions at different temperatures and compositions. A hypothetical binary model has been applied to find the dependencies of parameters of this equation of state on solution temperature and composition. Using such a simple model the heat capacity of NaCl solution was calculated for which the absolute percent deviation is less than 2 %. The DSEOS is tested for the following electrolytes: Na2SO4, MgCl2, MgSO4, KCl, NaCl, and NaBr. We found that... 

    Thermodynamic Properties of Aqueous Electrolyte Solutions Containing Urea

    , M.Sc. Thesis Sharif University of Technology Samieenasab, Ahmad Reza (Author) ; Ghotbi, Siroos (Supervisor) ; Taghikhani, Vahid (Supervisor)
    Abstract
    The behavior of biomolecules in mixtures is affected by the presence of electrolytes. For instance, in the presence of an electrolyte, solubility of most biomolecules like proteins,peptids and amino acids can be increased or decreased. As a biomolecule, urea is a protein denaturant and influences protein folding and protein-DNA binding. The presence of ions can affect the interactions between urea and water In this thesis, experimental data of density and electrical conductance of aqueous solutions of urea-NaCl were obtained at different physical conditions. Density measurement experiments were carried out at different temperatures from 20-40 oC. Apparent and infinite dilution molar volumes... 

    Experimental Study and Modeling of Saturation Molality of Inorganic Salts in formation water

    , M.Sc. Thesis Sharif University of Technology Sahraei, Sadegh (Author) ; Taghikhani, Vahid (Supervisor) ; Ghotbi, Sirous (Supervisor) ; Yousefi, Leyla (Co-Advisor)
    Abstract
    Saturation molality for a number of single and mixed aqueous electrolyte solutions containing NaCl, Na2CO3, and K2SO4, was measured at atmospheric pressure over a wide range of temperature. In order to check the repeatability of the experimental data, the experiments were replicated three times and average of the results was considered as final saturation molality. Experimental data of saturation molality for single electrolyte solutions were correlated using the modified UNIFAC–Dortmund model to account for the shortrange interaction. Binary interaction parameters, between water molecules and ionic species were also reported. For the long-range interactions between the ionic species in... 

    Correlation and prediction the activity coefficients and solubility of amino acids and simple peptide in aqueous solution using the modified local composition model

    , Article Fluid Phase Equilibria ; Volume 255, Issue 2 , 2007 , Pages 160-166 ; 03783812 (ISSN) Pazuki, G. R ; Taghikhani, V ; Vossoughi, M ; Sharif University of Technology
    2007
    Abstract
    In this work, the modified Wilson model was used to obtain the activity coefficients of amino acids and simple peptides in non-electrolyte aqueous solutions. The Wilson model was modified using the new local mole fraction proposed by Zhao et al. and non-random case for the reference state. The binary interaction parameters (BIP) of the modified Wilson model for amino acid-water pairs were obtained using the experimental data of the activity coefficients for amino acids available in the literature. The modified Wilson model was also used to correlate the solubility of amino acids in water and the values of Δh/R, Δs/R, and Δg/R of the solutions studied were reported. The results obtained... 

    Modeling electrolyte solutions with the SAFT-VR equation using Yukawa potentials and the mean-spherical approximation

    , Article Fluid Phase Equilibria ; Volume 236, Issue 1-2 , 2005 , Pages 241-255 ; 03783812 (ISSN) Behzadi, B ; Patel, B. H ; Galindo, A ; Ghotbi, C ; Sharif University of Technology
    Elsevier  2005
    Abstract
    An equation of state based on the statistical associating fluid theory for potentials of variable range (SAFT-VR) is used to model 7 hydrogen-bonding solvents and 23 electrolyte solutions. Solvent-solvent hydrogen bonding interactions are explicitly taken into account as in other versions of the SAFT approach. In addition, long-range Coulombic interactions between ionic species are accounted for using the non-restricted mean-spherical approximation, while solvent-solvent and solvent-ion dispersion interactions are included and are treated using Yukawa potentials. Previously a similar approach had been proposed in which the dispersion interactions were treated using square-well potentials. In... 

    Application of the MSA-based models in correlating the surface tension for single and mixed electrolyte solutions

    , Article Journal of Chemical Thermodynamics ; Volume 41, Issue 11 , 2009 , Pages 1264-1271 ; 00219614 (ISSN) Sadeghi, M ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
    2009
    Abstract
    Experimental values for surface tension of single and mixed electrolyte solutions were correlated using the models based on the perturbation theory. The Mean Spherical Approximation (MSA) model, coupled with the Ghotbi-Vera (GV) and the Mansoori et al. (BMCSL) equations of state, were used to correlate the experimental values of the surface tension. The results showed that the models can favourably correlate the experimental values for single electrolyte solutions. However, it was observed that the GV-MSA model can more accurately predict the surface tension for single electrolytes, especially at higher concentrations. Two different expressions for concentration dependency of cation hydrated... 

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

    , Ph.D. Dissertation Sharif University of Technology Sadeghi, Masoud (Author) ; Abdekhodaie, Mohammad Jafar (Supervisor) ; Ghotbi, Cyrus (Co-Advisor)
    Abstract
    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... 

    Modification of the GV-MSA model in obtaining the activity and osmotic coefficients of aqueous electrolyte solutions

    , Article Fluid Phase Equilibria ; Volume 240, Issue 2 , 2006 , Pages 167-172 ; 03783812 (ISSN) Mortazavi Manesh, S ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
    2006
    Abstract
    In this work a modified form of the Ghotbi-Vera Mean Spherical Approximation model (MGV-MSA) has been used to correlate the mean ionic activity coefficients (MIAC) for a number of symmetric and asymmetric aqueous electrolyte solutions at 25 °C. In the proposed model the hard sphere as well as the electrostatic contributions to the MIAC and the osmotic coefficient of the previously GV-MSA model has been modified. The results of the proposed model for the MIAC of the electrolyte solutions studied in this work are used to directly calculate the values of the osmotic coefficients without introducing any new adjustable parameter. In the MGV-MSA model the cation diameter as well as the relative... 

    Application of the GV-MSA model to the electrolyte solutions containing mixed salts and mixed solvents

    , Article Fluid Phase Equilibria ; Volume 231, Issue 1 , 2005 , Pages 67-76 ; 03783812 (ISSN) Salimi, H. R ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
    2005
    Abstract
    In this work the Ghotbi-Vera mean spherical approximation (GV-MSA) model, coupled with two different expressions for the cation-hydrated diameters, was used in predicting the mean ionic activity coefficients (MIAC) of electrolytes for a number of the mixed-solvent and mixed-salt electrolyte solutions at 25 °C. In all cases the cation diameters in solutions changed with concentration of electrolyte while the anion diameters were considered to be constant and equal to the corresponding Pauling diameters. In application of the GV-MSA model to the electrolyte systems, two different expressions were used for concentration dependency of cation-hydrated diameters, i.e., the GV-MSA1 and GV-MSA2... 

    Application of the Pitzer and the MSA-based models in predicting the activity and the osmotic coefficients of aqueous electrolyte solutions

    , Article Scientia Iranica ; Volume 12, Issue 3 , 2005 , Pages 280-289 ; 10263098 (ISSN) Azimi, G ; Ghotbi, C ; Taghikhani, V ; Sharif University of Technology
    Sharif University of Technology  2005
    Abstract
    The GV-MSA, the BMCSL-MSA and the Pitzer models were used to correlate the individual, the mean ionic activity coefficients and the osmotic coefficients of symmetric and asymmetric electrolyte solutions. In order to compare the results obtained from the GV-MSA with those obtained from the Pitzer and the BMCSL-MSA models, the same experimental data and the same minimization procedure were used and the new sets of parameters for the BMCSL-MSA and the Pitzer models were also reported. The values for the osmotic coefficients of electrolyte solutions were calculated directly using the values of the mean ionic activity coefficients obtained from the models studied in this work. The results for the... 

    Measurement and correlation of surface tension for single aqueous electrolyte solutions

    , Article International Journal of Thermophysics ; Volume 31, Issue 4-5 , May , 2010 , Pages 852-859 ; 0195928X (ISSN) Sadeghi, M ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
    2010
    Abstract
    In this study, the values of the surface tension for a number of single aqueous electrolyte solutions were measured at various temperatures and electrolyte concentrations using the well-known and computer-aided pendant-drop method. In order to conduct the experimental measurements, a high-pressure IFT-700 apparatus, equipped with a view cell and a data acquisition system, was used. The systems studied in this study were aqueous solutions of KCl, NaCl, CaCl 2, and Na 2SO 4. The pooled standard deviation and the confidence limit of the surface-tension data for a 95 % confidence level were determined to be 0.17mN · m -1 and σ̄ ± 0.19, respectively. It should be noted that while the surface... 

    Prediction of the aqueous solubility of BaSO4 using pitzer ion interaction model and LSSVM algorithm

    , Article Fluid Phase Equilibria ; Vol. 374, issue , July , 2014 , p. 48-62 ; ISSN: 03783812 Safari, H ; Shokrollahi, A ; Jamialahmadi, M ; Ghazanfari, M. H ; Bahadori, A ; Zendehboudi, S ; Sharif University of Technology
    Abstract
    Deposition of barium sulfate (or BaSO4) has already been recognized as a devastating problem facing process industries and oilfield operations, mainly owing to its low solubility in aqueous solutions. Predicting and also preventing the overall damage caused by BaSO4 precipitation requires a profound knowledge of its solubility under different thermodynamic conditions. The main aim of this study is to develop a solubility prediction model based on a hybrid of least squares support vector nachines (LSSVM) and coupled simulated annealing (CSA) aiming to predict the solubility of barium sulfate over wide ranges of temperature, pressure and ionic compositions. Results indicate that predictions of... 

    A new model in correlating the activity coefficients of aqueous electrolyte solutions with ion pair formation

    , Article Fluid Phase Equilibria ; Volume 261, Issue 1-2 , December , 2007 , Pages 313-319 ; 03783812 (ISSN) Mortazavi Manesh, S ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
    2007
    Abstract
    In this work, the Ion Pair Modified Ghotbi-Vera Mean Spherical Approximation (IP-MGV-MSA) model was proposed to correlate the mean ionic activity coefficients (MIAC) for a number of symmetric and asymmetric aqueous electrolyte solutions at 25 °C. The new model is based on the recently proposed MGV-MSA model by Mortazavi-Manesh et al. In the IP-MGV-MSA model, the effects arising from the ion pair formation in the electrolyte solution was taken into account. Also, in the proposed model, while the cation diameter as well as the relative permittivity of water was considered to be dependent on electrolyte concentration, the anion diameter was independent of electrolyte concentration. The results... 

    Experimental study and modelling of saturation molality of NaCl in quaternary aqueous electrolyte solutions at various temperatures

    , Article Desalination ; Volume 267, Issue 2-3 , February , 2011 , Pages 228-232 ; 00119164 (ISSN) Yousefi, L ; Roayaei, E ; Taghikhani, V ; Safekordi, A ; Zahedzadeh, M ; Sharif University of Technology
    2011
    Abstract
    Saturation molality of sodium chloride in mixed aqueous electrolyte solutions containing NaCl, CaSO4 and Na2SO4 was measured at atmospheric pressure over the wide range of temperatures using an equilibrium cell equipped with an accurate temperature control system. The measurements were carried out at different CaSO4 and Na2SO4 concentrations. In order to check the repeatability of the experimental data for the saturation molality of NaCl, the experiments were replicated three times and the values reported were the average of the replicas. To model the data generated in this work, the PDH+UNIFAC-Dortmund activity coefficient model was used. The model used to predict the mean ionic activity... 

    Thermodynamics and Kinetics Study of Gas Hydrates in Presence of Ionic Liquids

    , M.Sc. Thesis Sharif University of Technology Sahraei, Vahab (Author) ; Ghotbi, Cyrus (Supervisor) ; Taghikhani, Vahid (Supervisor) ; Nazari, Khodadad (Supervisor)
    Abstract
    Gas hydrates are ice-like clathrate compounds. Methane, carbon dioxie and natural gas compounds can form gas hydrate and plug pipelines, in order to preventing of gas hydrate formation, inhibitors like electrolytes are added to the natural gas pipelines. In this work a model proposed to predict the hydrate formation conditions in presence of some inhibitors such as NaCl, KCl, NaBr, KBr, [BMIM][BF4] and [BMIM][Br]. So a new equation of state that can be applied to both electrolyte and associating solutions called GV-SAFT-MSA is developed. Two dialkylimidazolium ionic liquids [BMIM][BF4] and [BMIM][MS] have been investigated for their potential application as novel gas hydrate inhibitors. The... 

    Heat transfer characteristics of mixed electroosmotic and pressure driven flow of power-law fluids in a slit microchannel

    , Article International Journal of Thermal Sciences ; Volume 53 , 2012 , Pages 71-79 ; 12900729 (ISSN) Babaie, A ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
    2012
    Abstract
    Thermal transport characteristics of electroosmotic flow of power-law fluids in the presence of pressure gradient through a slit microchannel are studied in this paper. Considering a fully developed flow with a constant wall heat flux as the boundary condition, the governing equations are numerically solved by means of the finite difference method. A complete parametric study is done in order to investigate the effects of different flow parameters on the thermal behaviors of the flow. The results show that the non-Newtonian characteristic of the fluid can influence the thermal behaviors of the flow by affecting the rate of heat convection and viscous dissipation; however, its influence...