Faculty of Applied Sciences
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Item Density, speed of sound, refractive index and activity coefficients at infinite dilution for ionic liquids(2018) Mgxadeni, Ncomeka; Deenadayalu, Nirmala; Ramjugernath, Deresh; Naidoo, ParamespriIn this study the experimental density, speed of sound, and refractive index for binary mixtures of an ionic liquid (IL): 1-butyl-3-methylimidazolium nitrate and activity coefficients at infinite dilution of organic solutes in the ionic liquid: 1-butyl-3-methylimidazolium hydrogen sulfate were determined. The density, speed of sound, and refractive index of 1-butyl-3-methylimidazolium nitrate in pyridine or acetonitrile or thiophene have been reported at T = 298.15 K, 303.15 K, 308.15 K, 313.15 K and 318.15 K using an Anton Paar DSA 5000M vibrating U-tube densimeter and a RXA 156 refractometer. The derived properties namely: excess molar volume, isentropic compressibility and change in refractive index were calculated from density, speed of sound and refractive index, respectively. The results are discussed in terms of molecular interactions (hydrogen bond, dipole-dipole, or ion-solvent or interactions). The negative deviation of excess molar volume and the positive deviation in change in refractive index clearly indicates the strong interaction of 1-butyl-3-methylimidazolium nitrate with pyridine or acetonitrile or thiophene in solution. The positive values of isentropic compressibility for the system indicates that the mixtures were more compressible than the ideal mixture. The Redlich Kister smoothing polynomial was used to fit the excess molar volume and deviation in isentropic compressibility data. The Lorentz-Lorenz equation was used to predict the experimental density, or refractive index data and to correlate the excess molar volume. Gas liquid chromatography was used to determine activity coefficients at infinite dilution for 28 polar and non-polar organic solute: alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, aldehydes, thiophene, pyridine and acetonitrile in an IL: 1-butyl-3- methylimidazolium hydrogen sulfate ([BMIM][HSO4]). The measured values of activity coefficients at infinite dilution for the solutes in [BMIM][HSO4] were carried out at T = (313.15, 323.15, 333.15) K. Partial molar excess enthalpies at infinite dilution of the organic solutes in the ionic liquid have been calculated from the temperature dependence of activity coefficients at infinite dilution. The selectivity and capacity values for separation problems namely: hexane/benzene, heptane/benzene, cyclohexane/benzene, ethanol/benzene, heptane/pyridine, heptane/thiophene and methanol/acetone at T = 323.15 K were calculated and compared to literature values for similar ionic liquids, sulfolane and N-methyl-2- pyrolidinone (NMP). The IL [BMIM][HSO4] gave both the highest selectivity and limiting capacity for the heptane/thiophene separation and would therefore be a suitable entrainer for this separation. New data from this study reveals that [BMIM][HSO4] may be proposed as a replacement solvent for the separation of sulphur or nitrogen compounds from alkanes.Item Volumetric, acoustic and refractive index for the binary system (Butyric acid + Hexanoic acid) at different temperatures(Springer, 2014-04-12) Bahadur, Indra; Deenadayalu, Nirmala; Naidoo, Paramespri; Ramjugernath, DereshIn this paper density, sound velocity, and refractive index for the binary system (butyric acid ? hexanoic acid) were measured over the entire composition range and at 5 K intervals in the temperature range 293.15–313.15 K. The excess molar volumes, isentropic compressibilities, excess isentropic compressibilities, deviation in refractive indices, molar refractions, and deviation in molar refractions were calculated by using the experimental densities, sound velocities, and refractive indices, respectively. The Redlich–Kister equation was used to fit the excess molar volume, excess isentropic compressibility, deviation in refractive index and deviation in molar refraction data. The Lorentz–Lorenz approximation was used to correlate the excess molar volume from the deviation in refractive index and also to predict the density from refractive index or the refractive index from density of the binary mixtures. Four sound velocity mixing rules were tested and the best model for the systems studied in this work was the Berryman mixing rule. The thermodynamic properties are discussed in terms of intermolecular interactions between the components of the mixtures.Item Effect of temperature on density, sound velocity, refractive index and their derived properties for the binary systems (heptanoic acid + propanoic or butanoic acids)(Elsevier, 2014-06-14) Bahadur, Indra; Naidoo, Paramespri; Singh, Sangeeta; Ramjugernath, Deresh; Deenadayalu, NirmalaIn this work, the effect of temperature on density (q), sound velocity (u), refractive index (n) and their derived properties for carboxylic acid mixtures was studied. The thermophysical properties: density, sound velocity and refractive index were measured over the entire composition range at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K and at p = 0.1 MPa for the binary systems (heptanoic acid + propa-noic or butanoic acids). The mass fraction of water was found to be unusually large and could not be reduced further. The Lorentz–Lorenz approximation was used to predict the density from refractive index or the refractive index from density of the binary mixtures. Sound velocity mixing rules were applied to the experimental sound velocity data. Excess molar volumes, VEm; isentropic compressibilities, js, excess isentropic compressibilities, jsE, and deviation in refractive indices, Dn, were also calculated from the experimental data. The Redlich–Kister polynomial equation was fitted to the excess properties and the deviation in refractive index data. Thermophysical properties are useful in understanding the intermolecular interactions between the components of mixtures.Item Influence of alkyl group and temperature on thermophysical properties of carboxylic acid and their binary mixtures(Elsevier B.V., 2014-06-30) Bahadur, Indra; Deenadayalu, Nirmala; Naidoo, Paramespri; Ramjugernath, Deresh; Singh, Sangeetan this work, volumetric, acoustic and refractive index methods have been used to study the interactions between carboxylic acids mixtures as a function of temperature and concentration. The density (r), sound velocity (u), refractive index (n) of butanoic acid, pentanoic acid and heptanoic acid and their binary systems (butanoic or heptanoic acid + pentanoic acid) have been measured at 293.15, 298.15, 303.15, 308.15 and 313.15 K and at p = 0.1 MPa. The Lorentz–Lorenz approximation and sound velocity mixing rules were used to test the accuracy of the experimental data. The derived properties such as excess molar volumes, VEm, isentropic compressibilities, ks, excess isentropic compressibilities, ksE, and deviation in refractive indices, Dn, were also calculated. The Redlich–Kister polynomial equation was used to fit the excess/deviation properties. These results are useful for describing the intermolecular interactions that exist between the components in mixtures. This work also tests various sound velocity mixing rules to calculate the sound velocity of the binary mixture from pure component data, as well as examine the use of the Lorentz–Lorenz approximation to predict density from refractive index and vice versa.