Eva Rodil

Physical and equilibrium properties of diisopropyl ether+isopropyl alcohol+water system

Abstract Molar volume, isentropic compressibility, and molar refraction changes of mixing of the system diisopropyl ether (DIPE)+isopropyl alcohol (IPA)+water were determined at 298.15 K. These deviational properties were satisfactorily correlated with the composition data by means of Redlich–Kister polynomials. Tie line data have been determined at 298.15, 308.15, and 318.15 K for the ternary liquid–liquid equilibria, and were adequately correlated by means of the NRTL and UNIQUAC equation, and compared with results predicted by the UNIFAC method.

Direct Preparation of Sulfide Semiconductor Nanoparticles from the Corresponding Bulk Powders in an Ionic Liquid

The physicochemical properties of materials depend on their particle size. Appealing properties can be imparted to different materials at nanometric levels, thus generating a new range of interesting and promising products with different optical, electronic, magnetic, chemical, and mechanical properties from those of the bulk materials. In particular, semiconductor nanoparticles, and more specifically chalcogenide nanoparticles, have been intensively studied because of their quantum confinement effects and size-dependent photoemission characteristics. These semiconductor nanoparticles are widely used for biological labeling and diagnosis, light-emitting diodes, electroluminescent and photovoltaic devices, lasers, single-electron transistors, and catalysis. Over the last decades, a great effort has been made in the development of approaches for the synthesis of nanoparticles with controlled size and shape, as well as on the study of their properties. Among these approaches, liquid-phase methods (which comprise both microemulsion and reaction techniques) are the most relevant because of their simplicity and ability to control the nanoparticles morphology according to the operation conditions. Ionic liquids are salts with low (< 100 8C) melting temperatures. They typically exhibit properties such as extremely low vapor pressures, wide liquid ranges, ability to dissolve a broad variety of compounds, and good thermal and chemical stabilities. Moreover, by judicious selection of the cation– anion combination (“design” of the ionic liquid), it is possible to adjust the properties of the ionic liquid to a considerable extent to match those required for a given application. These characteristics render them as interesting compounds for the development of more sustainable processes in a great variety of applications in different fields. Subsequent to a burgeoning in research on ionic liquids in the late 1990s, they were first used in a method for the preparation of nanoparticles about a decade ago. Since then, it has been proposed that ionic liquids may provide both steric and electrostatic stabilization to nanoparticles, and they have been used in a variety of roles (e.g., (co)solvents, reactants, templates) in a good number of methods for the synthesis of inorganic nanoparticles with novel morphologies and improved properties. Nanomaterials preparation methods involving ionic liquids have been mostly applied to the synthesis of metal nanoparticles, although the preparation of metal oxide nanoparticles is gaining increasing attention. Also, other nanoparticles of interest such as metal chalcogenides, in particular sulfides, have been synthesized using methods based on ionic liquids. For example, CdS and PbS nanoparticles were prepared in the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate, using ultrasonic irradiation, with thioacetamide and the corresponding metal acetate as precursors. In another example, ZnS nanoparticles were prepared from zinc acetate in the ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate, by a microwaveassisted method. In spite of the introduction of ionic liquids in liquid-phase methods for the preparation of nanoparticles, the utilization of organic solvents and/or solid precursors, which have associated undesired effects from a perspective of sustainability, has remained necessary. Herein, we present a novel method (Figure 1), in which only an ionic liquid and the bulk powder of the material of the target nanoparticle are used,

Molar Volume, Molar Refraction, and Isentropic Compressibility Changes of Mixing at 25°C for the System Ethanol + Methanol + Dibutyl Ether

The densities, refractive indexes, and sound velocities for mixtures of ethanol + methanol + dibutyl ether at 25°C and atmospheric pressure, were determined and used to calculate molar volumes, molar refractions, and isentropic compressibilities. The excess molar volumes and the deviations of molar refractions and isentropic compressibilities from mole fraction and volume fraction averages, respectively, of these properties of the pure components were satisfactorily correlated with the composition data by means of the Redlich–Kister polynomial.

(Vapour + liquid) equilibrium of (DIPE + IPA + water) at 101.32 kPa

Thermodynamically consistent (vapour + liquid) equilibrium data at 101.32 kPa have been determined for (diisopropyl ether + isopropyl alcohol + water) and its constituents (diisopropyl ether + isopropyl alcohol) and (isopropyl alcohol + water). The NRTL and UNIQUAC equations for the liquid phase activity coefficients were found to correlate better the experimental data. The ASOG and the original and modified UNIFAC group-contribution methods did not represent adequately the (vapour + liquid) equilibrium data of this study.

Surfactant precipitation and polar solvent recovery of α-chymotrypsin and ribonuclease-A

Abstract The purification of two enzymes, α-chymotrypsin and ribonuclease-A, was studied using sodium di-(2-ethylhexyl) sulfosuccinate (AOT) as precipitating ligand. The enzymes formed a water insoluble complex upon contact with AOT and precipitated from the aqueous solution. The molar ratio between AOT and the targeted enzyme, required to obtain a 100% precipitation from an aqueous solution, was 7 for α-chymotrypsin and 13 for ribonuclease-A. Acetone was then used to recover the enzymes from the protein-AOT insoluble complex. The enzyme precipitated as white solid, while the surfactant remained in the acetone phase. The recovered enzyme was free of surfactant and retained its original enzymatic activity. The selectivity of this precipitation method was a strong function of the isoelectric point (pI) of proteins indicating that the ionic interactions between oppositely charged protein and AOT is the driving force for precipitation. Proteins with pI values within one pH unit, cannot be selectively separated using this method.

Thermodynamic behaviour of ethanol+methanol+2-ethoxy-2-methylpropane system. Physical properties and phase equilibria

Abstract The densities, refractive indices and speeds of sound of ternary ethanol+methanol+2-ethoxy-2-methylpropane (ETBE) mixtures were determined at 298.15 K and atmospheric pressure, and were used to calculate the corresponding excess molar volumes and the deviations of the molar refractive index and isentropic compressibility from linear dependence on concentration. These excess and deviational quantities were best predicted by the equations of Radojkovic, Kohler and Jacob and Fitzner. Vapour–liquid equilibrium (VLE) data were obtained for the ternary system at 101.32 kPa, shown to pass thermodynamic consistency tests, correlated by means of the equations Wilson, NRTL and UNIQUAC, and compared with the results predicted by the ASOG-KT and original and modified UNIFAC methods and by the equations of Wilson, NRTL and UNIQUAC with interaction parameters obtained from data for the relevant binary systems. The agreement between the experimental data and the latter predictions was as good as was achieved by ASOG-KT and UNIFAC-Dortmund, which were the best of the group contribution methods.

Measurement and prediction of isobaric vapour–liquid equilibrium data of the system ethanol+methanol+2-methoxy-2-methylpropane

Abstract Isobaric vapour–liquid equilibria for the system ethanol+methanol+MTBE were determined at 101.32 kPa. These data for this ternary system were then compared with predictions made using the Wilson, NRTL and UNIQUAC equations and the binary interaction parameters for the corresponding constituent binary subsystems. The predictions deviated only slightly from the experimental data. Moreover, these deviations were smaller than those obtained when the equilibrium data were predicted using the ASOG, UNIFAC, UNIFAC-Lyngby or UNIFAC-Dortmund group-contribution methods, among which the latter method afforded the most satisfactory predictions.

Precipitation and recovery of cytochrome c and hemoglobin using AOT and acetone

Abstract The precipitation of two transport proteins, cytochrome c and hemoglobin, was carried out by using di‐(2‐ethylhexyl) sulfosuccinate, known as aerosol‐OT (AOT), as a precipitating agent. The percent precipitation was 100% when the molar ratio between AOT and the targeted protein was 11 for cytochrome c and 30 for hemoglobin. By using acetone as a polar solvent, the maximum recovery obtained was 98% for cytochrome c and 40% for hemoglobin. The surfactant contamination in the recovered product was below the detection limit. The required usage of surfactant to purify 1 mole of targeted protein was many orders of magnitude smaller than that required for a reverse micellar extraction when using AOT. Advantages of the suggested precipitation method over the reverse micellar extraction method for protein purification are discussed.

Use of physical properties for compositional analysis of ternary mixtures. Application to mixtures of 2-methoxy-2-methylbutane, methanol, and 2,2,4-trimethylpentane or methylcyclohexane

Two ternary systems comprising gasoline components were characterized by determining their refractive indexes, densities, sound transmission speeds, and isentropic compressibilities at 25°C and 1 atm pressure. These data were then correlated with composition using a polynomial. Single measurements of the refractive index and density of fully miscible mixtures of the system 2-methoxy-2-methylbutane (TAME) + methanol + 2,2,4-trimethylpentane allowed estimation of its composition with precision better than ±0.002 mole fraction. However, it was shown that this approach to compositional analysis of homogeneous mixtures of TAME + methanol + methylcyclohexane would not give reliable results.

Phase equilibria involved in extractive distillation of 2-methoxy-2-methylpropane+methanol using 1-butanol as entrainer

Abstract Consistent vapour–liquid equilibrium (VLE) data at 101.32 kPa have been determined for the ternary system 1-butanol+methanol+2-methoxy-2-methylpropane, correlated by means of the Wilson, NRTL, and UNIQUAC equations, and compared with the results predicted by using the same equations with interaction parameters obtained from data for the relevant binary systems. The predictions deviated only slightly from the experimental data. The Wilson equation provided the most satisfactory prediction. Moreover, deviations were smaller than those obtained when the equilibrium data were predicted using the ASOG-KT and the original and modified UNIFAC group-contribution methods. The results obtained with a commercial simulator (ChemCAD IV) indicate that extractive distillation with 1-butanol as entrainer is a feasible method for the separation of 2-methoxy-2-methylpropane (MTBE) and methanol.