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Noroozi J.,Sharif University of Technology | Ghotbi C.,Sharif University of Technology | Sardroodi J.J.,Shahid Madani University of Azarbaijan | Karimi-Sabet J.,Jaber Ebne Hayyan National Research Laboratory | Robert M.A.,Rice University
Journal of Supercritical Fluids | Year: 2016

Classical molecular dynamics simulations are used to compute the solvation free energy of two pharmaceutical solids, namely ibuprofen and acetaminophen in carbon dioxide (CO2), over the density range of interest in supercritical processes. In order to examine the influence of the solvent model on the resulting free energies, three popular CO2 models (Zhang, EPM2, and TraPPE) are studied. Relatively large discrepancies for the solvation free energy exist between these CO2 models, suggesting that the former is sensitive to the different balances between dispersive and electrostatic forces used in these models. In particular, for the solvation of the highly polar (dipole moment of ∼5.2 Debye) acetaminophen molecule, such discrepancies are more pronounced than for the moderately polar ibuprofen (dipole moment of ∼1.6 D) molecule. Since there is an exponential relationship between the solvation free energy and solubility, the choice of the solvent model substantially affects the predicted solubility. For the solubility of the studied solutes, the value obtained using the TraPPE model is the highest, that of the EPM2 model is intermediate, and that of the Zhang model is the lowest. Generally, the simulations results show that the model with the largest quadrupole moment leads to a more negative solvation free energy and a higher solubility over the entire density range. Further, the decomposition of the solvation free energy into contributions stemming from electrostatics and dispersion interactions shows that the electrostatic interactions are important for a quantitative prediction of solid solubility, while the Lennard-Jones parameters of the solute and solvent are more important for qualitative agreement. Additionally, the infinite-dilution partial molar volume of the two solutes is estimated from the pressure derivative of the solvation free energies. With density increasing beyond the value corresponding to the zero partial molar volume of the solute (minimum solvation free energy), the repulsive part of Lennard-Jones potential wins over the attractive interactions, and the solvent strength of supercritical CO2 decreases; however, due to the increase in the chemical potential of the pure solid (effect of the Poynting correction), the solubility further increases. Overall, these results demonstrate the importance of a proper choice of quadrupole moment of the solvent model, which is crucial for quantitative predictions of the solid solubility in supercritical CO2. © 2015 Published by Elsevier B.V. Source


Masoodiyeh F.,University of Kashan | Mozdianfard M.R.,University of Kashan | Karimi-Sabet J.,Jaber Ebne Hayyan National Research Laboratory
Journal of Chemical Thermodynamics | Year: 2014

Presence of minute amount of inorganic salts in supercritical water (SCW) can cause equipment scaling, erosion and corrosion, reaction disturbance and process malfunctions. Thermodynamic modeling reduces experimental measurements; hence, solubility of several inorganic salts with available empirical solubility data (NaH2PO4, Na2HPO4, NaCl, CaCl2, MgCl2 and MgSO4) within temperature and pressure ranges of (623-823) K and (9.0-25.0) MPa, respectively, is estimated following determination of the dissociation constant, K, in SCW using three known models, namely, R-HKF, Sue-Adschiri-Arai (SAA) and Density model. Results obtained are compared with the experimental data to assess the suitability of the models in predicting the solubility of these inorganic salts in SCW, which indicate that R-HKF model is satisfactorily capable of correlating solubility for these salts. In almost every case except NaCl, SAA has provided similar estimation to R-HKF model. The Density model however, has offered the least accurate estimation in all cases. © 2014 Elsevier Ltd. All rights reserved. Source


Sadeghi M.H.,Sharif University of Technology | Outokesh M.,Sharif University of Technology | Karimi-Sabet J.,Jaber Ebne Hayyan National Research Laboratory
Separation Science and Technology (Philadelphia) | Year: 2016

ABSTRACT: Experimental study of the performance of a gas centrifuge can be appreciably simplified if instead of isotopic mixtures, a binary mixture of gases with large molecular weight difference is used. The current study undertook this approach by injecting a 53%–47% (w/w) mixture of “Freon12-Freon22” into a gas centrifuge. The two parameters, whose investigation was the objective of the current study were: the feed flow rate (F), and the clearance between tail scoop and the rotor wall (d). The results demonstrated that changing the scoop-wall clearance has the most significant effect on the cut (θ), so that by fixing “d”, “θ” becomes nearly invariant. The head separation factor (α) exhibited the same dependency, but it was more influenced by the “F” than the “d”. Apparently the following regression exists between the inspected parameters: Decreasing “d” → Decreasing “θ” → Increasing “α”. Variations of the tail separation factor (β) with “F” or “d” was quite slight, even though similar to “α”, it was lowered with increasing of the “F”. The separation capacity (δU) as the most significant parameter of a centrifuge was optimised at the highest value of “F = 40.5 g/h”, and lowest value of “d = 3 mm”. The study achieved a separation capacity and an overall separation factor equal to 195.53 kg Freon/y and 16.87, respectively. These values are several times larger than those of the isotopic mixtures, demonstrating that application of Freons is a useful mean for magnifying the features of a gas centrifuge. © 2016 Taylor & Francis. Source


Amanlou M.,Tehran University of Medical Sciences | Karimi-Sabet J.,Jaber Ebne Hayyan National Research Laboratory | Golestani A.,Tehran University of Medical Sciences
Journal of Nano Research | Year: 2015

The purpose of this study was to prepare ibuprofen loaded solid lipid nanoparticles (IBUSLNs) that is, effective in oral drug delivery. IBU-SLNs were synthesized by co-precipitation of rapid expansion of supercritical solution (CO-RESS). The produced SLNs consisted of stearic acid as lipid matrix. The unprocessed stearic acid, ibuprofen and IBU-SLNs were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), fourier transform infrared spectrophotometry (FTIR) and high performance liquid chromatography (HPLC). XRD patterns along with DSC showed that ibuprofen was present in both amorphous and crystalline form within lipid matrix. FTIR showed that molecular interactions that could alter the chemical structure of the IBU did not occur. The RESS process could produce ultrafine spherical particles of SLNs with high drug loading capacity. The IBU dissolution profile showed that the formulated SLNs have effectively increased the IBU solubility. © (2015) Trans Tech Publications, Switzerland. Source


Outokesh M.,Sharif University of Technology | Naderi A.,Sharif University of Technology | Khanchi A.R.,Sharif University of Technology | Khanchi A.R.,Jaber Ebne Hayyan National Research Laboratory | Karimi Sabet J.,Sharif University of Technology
Industrial and Engineering Chemistry Research | Year: 2014

Continuous adsorption in stirred reactors in the form of carbon in pulp (CIP) and resin in pulp (RIP) is an established process for the extraction of gold and uranium. Under the circumstance of intraparticle diffusion resistance, CIP and RIP have been accurately modeled by the Boyd's series (reversible adsorption) and shrinking core model (irreversible adsorption). The present study, in its first part, introduces an analytical formula that most closely approximates both models. Using such formula, the study addresses a basic algorithm for optimization of single-stage continuous adsorption systems through linking of the major process variables. Furthermore, this study is devoted to developing an "analytical kinetics approach" for the design of multistage CIP and RIP processes via application of Glauekauf's multiple series. Advantages of the new approach over the McCabe-Thiele "Equilibrium Approach" are (1) the incorporation of the kinetics and equilibrium into one unified model, and (2) accurate determination of the number of stages, reactor size, and optimum operational conditions. © 2013 American Chemical Society. Source

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