Faculty of Applied Sciences
Permanent URI for this communityhttp://ir-dev.dut.ac.za/handle/10321/5
Browse
3 results
Search Results
Item Thermodynamic properties at infinite dilution of deep eutectic solvents with organic solutes at different temperatures(2023) Manyoni, Lindokuhle; Redhi, Gan G.Many industrial processes in the chemical industry require surge amounts of energy to separate organic mixtures. While numerous separating substances used for this purpose are volatile and have closely related boiling points to the mixtures, they are environmentally harmful. As a result, new separation substances in the space of these solvents should be researched. The latest group of solvents known as deep eutectic solvents (DESs), classified as Type (III), were studied in the space of conventional organic solvents, which are currently used in industrial processes for extraction or separation purposes. In the forecast, deep eutectic solvents have gained significant interest as part of the low melting temperature solvents with many other attractive and unique properties. This includes their physical, thermophysical, and thermodynamic properties. These properties were investigated in this study in order to better understand the intermolecular interactions of 1-ethyl-1-methylpyrrolidinium bromide + glycerol [(EMPYR) Br + Gly] or 1-ethyl1-methylpyrrolidinium bromide + ethylene glycol [(EMPYR) Br + EG], with methanol or ethanol. Hence, the first section of the study investigated the physical properties, including density and sound velocity, of deep eutectic solvents and their binary mixtures, as a function of temperature. The obtained physical properties were used to compute the thermophysical properties, i.e., excess molar volume (Vm E ), intermolecular free length (Lf), variation in isentropic compressibility (∆Ks), and isentropic compressibility (Ks ), to advance the study of the intermolecular interactions of the selected deep eutectic solvents and their binary mixtures. Furthermore, the second section of this study investigated the infinite dilution activity coefficients of five different deep eutectic solvents, including (1) 1-ethyl-1-methylpyrrolidinium bromide + glycerol [(EMPYR) Br + Gly], (2) 1-ethyl-1-methylpyrrolidinium bromide + ethylene glycol [(EMPYR) Br + EG], (3) 1-ethyl-1-methylpyrrolidinium bromide + 1-pentanediol [(EMPYR) Br + 1.5-PDO], (4) 1-ethyl-1-methylpyrrolidinium bromide + 1-hexanediol [(EMPYR) Br + 1.6- HDO], and (5) trihexyltetradecylphosphonium decanoate + ethylene glycol [(THTDP) Dc + EG], with various solutes at different temperatures. The obtained infinite dilution activity coefficients (γ13 ∞ ) were utilized to compute the other thermodynamic properties, viz., enthalpy (∆H1 E,∞), entropy (∆S1 E,∞), and Gibbs free energy (∆G1 E,∞) as well as the selectivity (Sij ∞) and capacity (kj ∞), of the selected organic solutes. The separation was possible with the investigated solvents. As is known, the accurate and precise analysis of the thermodynamic properties of liquid substances such as deep eutectic solvents is of significant interest to the chemical industry as it would help ascertain the implementation of these solvents on a large scale for industrial separation processes.Item Thermodynamic properties of selected ionic liquids with carboxylic acids at several temperatures(2019-08-19) Ogundele, Oriyomi Pelumi; Redhi, Gan G.; Moodley, Kandasamy G.Over the years, ionic liquids (ILs) have become an essential tool in chemistry owing to their various applications such as catalysis, electrochemistry, pharmaceuticals, nanotechnology, biotechnology, separation and extraction processes, amongst many others. With respect to the above applications, ionic liquids have desired properties like low flammability, low vapour pressure, high thermal and chemical stability, good electrical conductivity and low volatility. Ionic liquids possess the ability of being “tailored” to meet specific needs for different applications due to the flexibility in their physicochemical properties. This is done by replacing or substituting the side chain length of cation or anion structure.This project focused on the thermodynamic as well as thermo-physical parameters of two-component combinations of ionic liquids (ILs) and carboxylic acids (ethanoic or propanoic or butanoic or pentanoic or 2-methylpropanoic acids) which were investigated at several temperatures. The ionic liquidsutilized for this research investigation includes: •1-ethyl-3-methylimidazolium ethylsulphate ([EMIM]+[EtSO4]−)•1-butyl-3-methylimidazolium methylsulphate ([BMIM]+[MeSO4]−)•N-2′, 3′-epoxypropyl-N-methyl-2-oxopyrrolidinium salicylate ([EPMpyr]+[SAL]−)•N-2′, 3′-epoxypropyl-N-methyl-2-oxopyrrolidinium acetate ([EPMpyr]+[OAC]−)•N-2′, 3′-dihydroxypropyl-N-methyl-2-oxopyrrolidinium chloride ([PYR-PDO]+[Cl]−)Density and speed of sound measurements were examined obtained for the following two component systems: {([EMIM]+[EtSO4]−) + pentanoic or 2-methylpropanoic acid, ([BMIM]+[MeSO4]−) + ethanoic or propanoic acid, ([EPMpyr]+[SAL]−) + ethanoic or propanoic acid, [EPMpyr]+[OAC]−+ propanoic or butanoic acid, [PYR-PDO]+[Cl]−+ ethanoic or propanoic or butanoic acid) throughout the concentration of the ionic liquid at T= (288.15, 293.15, 298.15, 303.15, 308.15 and 313.15) K). Parameters such as excess molar volumes (VmE), isentropic compressibilities (ks) is entropic compressibilities deviation (Δks) and intermolecular free length (Lf) were computed from the measured values of densities and speeds of sound.The experimental data revealed that densities and speeds of sound value decrease with rise in temperature. Furthermore, excess molar volumes and is entropic compressibility deviation for all systems studied were found to be negative and increased with a rise in temperature. The negative outcomes obtained for excessmolar volumes of all the two-component systems studied suggest chemical interactions occur between unlike molecules in the component mixtures. These interactions are ascribed to formation of weak bonds and electron donor and acceptor complexes. Furthermore, the interaction interstices of IL gave some space for the acids to achieve structural arrangement.The Redlich-Kister equation was used to correlate the derived parameters; VmE, Δks and Lf whereas a least squares method was utilized in determining the fitting parameters and standard errors. These was done to check the precision of the measured data and the standard deviations which show moderately lower values for VmE, Δks and Lf with the examined temperatures for all the binary systems.Item Thermodynamic properties of 1-ethyl-3-methylimidazolium ethyl sulphate with nitrogen and sulphur compounds at T = (298.15 - 318.15) K and P = 1 bar(2016) Chule, Siyanda Brian; Deenadayalu, NirmalaIn this work, the thermodynamic properties for the binary mixtures containing the ionic liquid (IL): 1-ethyl-3-methylimidazolium ethyl sulphate ([EMIM] [EtSO4]) were calculated. The binary systems studied were {pyridine (Py) or ethyl acetoacetate (EAA) or thiophene (TS) + [EMIM] [EtSO4]}. The results were interpreted in terms of the intermolecular interactions between the (pyridine + IL), (ethyl acetoacetate + IL), and (thiophene + IL) molecules. The physical properties: density, speed of sound, and refractive index were measured for the binary mixtures over the complete mole fraction range using an Anton Paar DSA 5000 M vibrating U- tube densimeter and an Anton Paar RXA 156 refractometer, respectively. The measurements were done at T = (298.15, 303.15, 308.15, 313.15, and 318.15) K and at p = 0.1 MPa. The experimental data was used to calculate the derived properties for the binary mixtures namely:- excess molar volume (V E ), isentropic compressibility (ks), molar refractions (R) and deviation in refractive index (Δn). For the binary mixtures, (Py or EAA or TS + IL), V E was negative throughout the whole composition range which indicates the existence of attractive intermolecular interaction between (pyridine + IL) and (ethyl acetoacetate + IL) for (thiophene + IL), V E was negative at low mole fraction of thiophene and became positive at high mole fraction of thiophene. For the binary mixtures (pyridine + IL), (ethyl acetoacetate + IL), ks was positive indicating that the binary mixtures were more compressible than the ideal mixture. For the binary mixture (thiophene + IL) ks was negative at low thiophene composition and positive at high composition indicating that the binary mixture was less compressible than the ideal mixture at low thiophene composition and more compressible at high composition of thiophene. The molar refraction, R, is positive for the (Py or EAA or TS + IL) binary systems at T = (298.15 – 318.15) K, molar refraction decreases as the organic solvent composition increases. For the binary mixture (pyridine + [EMIM] [EtSO4]), Δn is negative at mole fractions < 0.75 of pyridine and positive at mole fractions >0.75 at all temperatures and decreases with an increase in temperature. For the binary system (ethyl acetoacetate + [EMIM] [EtSO4]), Δn values are positive over the entire composition range and at all temperatures and increases with an increase in temperature. Δn values for the (thiophene + IL) system are negative for mole fractions of thiophene < 0.62 and becomes positive for mole fractions of thiophene > 0.62 and Δn increases with an increase in temperature. The Redlich-Kister smoothing equation was used successfully for the correlation of V E and Δn data. The Lorentz- Lorenz equation gave a poor prediction of V E , but a good prediction of density or refractive index.