Faculty of Applied Sciences
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Item Application of selected ionic liquids for different separation problems : liquid-liquid equilibria and activity coefficients at infinite dilution(2021) Kabane, Bakusele; Redhi, G. G.This work focusses on the application and pre-screening of selected ILs for different industrial separation problems based on limiting activity coefficients at infinite dilution, and liquid-liquid equilibrium data at different temperatures. The selected ionic liquids for pre-screening based on activity coefficients at infinite dilution data include (1,3- dimethyimidazolium dimethylphosphate, trioctylmethylammonium chloride, trihexyltetradecylphosphonium dicyanamide, 2,3-dihydroxypropyl-N-methyl-2- oxopyrrolidinium chloride, 2,3-epoxypropyl methyl-2-oxopyrrolidinium chloride) and deep eutectic solvent (1-butyl-3-methylimidazolium chloride + glycerol) at 1:2 molar ratio. These ionic liquids were tested in 33 solutes (alkanes, alkenes, alkynes, alcohols, tetrahydrofuran, ketones, aromatic hydrocarbons, thiophene, acetonitrile) and water at T = (313 – 343) K and at p = 101 kPa. The use of ionic liquid as a stationary phase on the column loading ranged between (30 – 36) % by mass. Thermodynamic functions at infinite dilution such as (Gibbs free energy, , entropy term, Tref and partial molar enthalpy, ) were also computed to further elucidate the types of intermolecular interactions existing between solutes and the investigated ionic liquids. The separation potential of the ionic liquids was determined from the selectivity ( ), and capacity ( ), values. Different ionic liquids (1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolim dicyanamide, 1,3-dimethylimidazolium dimethylphosphate) were also tested in the separation of azeotropic mixture (ethyl acetate/hexane) and in the desulfurization (thiophene/hexadecane or octane) process. The extraction process was conducted at varying temperatures, T = (308 and 298) K and at p = 101 kPa. The results were compared to previously published ionic liquids involving thermodynamic data found in the literature. The separation capacity was based on the calculated values of selectivities (S) and distribution ratio (β). The data was successfully correlated using the thermodynamic non-random two liquids (NRTL). From this study, it was found that the investigated ionic liquids showed some possible application for selected industrial separation problems.Item Thermodynamic properties of phosphonium-based ionic liquid mixtures at different temperatures(2018) Kabane, Bakusele; Redhi, Gan G.Ionic Liquids (ILs) are relatively newly formed types of solvents. As part of ongoing research, research groups and industries are focusing on solvents classified as ionic liquids, which have a low melting point,and they have been given great attention focusing on their thermophysical properties and applications. In order to utilize or industrially exploit these types of solvents, the understanding of intermolecular interactions and properties of pure liquids and their mixtures is important. Thermophysical properties of ionic liquid mixtures, especially density, viscosity and speed of sound are measured as a function of temperature. Accurate analysis on thermophysical properties of ionic liquids is more of paramount interest as they indicate the transformation of ionic liquids from small laboratory level to large-scale industrial implementation.In this study, new data for the binary mixtures containing {trihexyltetradecylphosphonium chloride ([P+14, 6, 6, 6] [Cl-]) IL and propanoic acid (PA)} and {1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]) + benzaldehyde or ethyl acetoacetate} were investigated under atmospheric pressure (p equivalent to 0.1 MPa) and at temperatures (293.15 to 313.15) K. Densities (ρ),viscosities (𝜂) as well as speeds of sound (𝑢)were measured over the whole range of mole fraction (𝑥𝑖= 0 to 1). The computed excess properties which includes excess molar volumes(𝑉mE), apparent molar volume (𝑉𝜙),intermolecular free length (Lf), isentropic compressibility(𝑘𝑠), deviations in viscosity (Δ𝜂), apparent molar isentropic compressibility (𝐾𝜙) and deviation in isentropic compressibility(Δ𝑘𝑠)were computed from the experimentally determined data of densities, viscosities and speeds of sound. In addition, measurements of activity coefficients at infinite dilution forvolatile organic compounds (alkenes, alcohols, alkanes, cycloalkanes, aromatic hydrocarbons, thiophene, ketones, acetonitrile, water and tetrahydrofuran) in the IL [trihexyltetradecylphosphonium-bis-(2, 4,4-trimethylpentyl)-phosphinate and trihexyltetradecylphosphonium chloride] were conducted at different temperatures.The obtained results and derived properties have been elucidated in terms of the interactions taking place among the solvent systems.