Please use this identifier to cite or link to this item: http://hdl.handle.net/10321/559
Title: Excess molar volume and isentropic compressibility for binary or ternary ionic liquid systems
Authors: Bahadur, Indra 
Issue Date: 2010
Abstract: The thermodynamic properties of mixtures involving ionic liquids (ILs) with alcohols or alkyl
acetate or nitromethane at different temperatures were determined. The ILs used were methyl
trioctylammonium bis(trifluoromethylsulfonyl)imide ([MOA]+[Tf2N]-) and 1-butyl-3-
methylimidazolium methyl sulphate [BMIM]+[MeSO4]-.
The ternary excess molar volumes (􀜸􀬵􀬶􀬷
E ) for the mixtures {methyl trioctylammonium bis
(trifluoromethylsulfonyl)imide + methanol or ethanol + methyl acetate or ethyl acetate}and (1-
butyl-3-methylimidazolium methylsulfate + methanol or ethanol or 1-propanol + nitromethane)
were calculated from experimental density values, at T = (298.15, 303.15 and 313.15) K and
T = 298.15, respectively. The Cibulka equation was used to correlate the ternary excess molar
volume data using binary data from literature. The 􀜸􀬵􀬶􀬷
E values for both IL ternary systems were
negative at each temperature. The negative contribution of 􀜸􀬵􀬶􀬷
E values are due to the packing
effect and/or strong intermolecular interactions (ion-dipole) between the different molecules.
The density and speed of sound of the binary solutions ([MOA]+[Tf2N]- + methyl acetate or
ethyl acetate or methanol or ethanol), (methanol + methyl acetate or ethyl acetate) and
(ethanol + methyl acetate or ethyl acetate) were also measured at T = ( 298.15, 303.15,
308.15 and 313.15) K and at atmospheric pressure. The apparent molar volume, Vφ , and the
apparent molar isentropic compressibility, κφ , were evaluated from the experimental density
and speed of sound data. A Redlich-Mayer type equation was fitted to the apparent molar
volume and apparent molar isentropic compressibility data. The results are discussed in terms
of solute-solute, solute- solvent and solvent-solvent interactions. The apparent molar volume
and apparent molar isentropic compressibility at infinite dilution, 􀜸φ
􀬴 and κφ
􀬴, respectively of
the binary solutions have been calculated at each temperature. The 􀜸φ
􀬴 values for the binary
v
systems ([MOA]+[Tf2N]- + methyl acetate or ethyl acetate or methanol or ethanol) and
(methanol + methyl acetate or ethyl acetate) and (ethanol + methyl acetate or ethyl acetate)
are positive and increase with an increase in temperature. For the (methanol + methyl acetate
or ethyl acetate) systems 􀜸φ
􀬴 values indicate that the (ion-solvent) interactions are weaker.
The κφ
􀬴 is both positive and negative. Positive κφ
􀬴, for ([MOA] + [Tf2N]- + ethyl acetate or
ethanol), (methanol + ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) can be
attributed to the predominance of solvent intrinsic compressibility effect over the effect of
penetration of ions of IL or methanol or ethanol. The positive κφ
􀬴 values can be interpreted in
terms of increase in the compressibility of the solution compared to the pure solvent methyl
acetate or ethyl acetate or ethanol. The κφ
􀬴 values increase with an increase in temperature.
Negative κφ
􀬴, for ([MOA] + [Tf2N]- + methyl acetate or methanol), and (methanol + methyl
acetate) can be attributed to the predominance of penetration effect of solvent molecules into
the intra-ionic free space of IL or methanol molecules over the effect of their solvent
intrinsic compressibility. Negative κφ
􀬴 indicate that the solvent surrounding the IL or
methanol would present greater resistance to compression than the bulk solvent. The κφ
􀬴
values decrease with an increase in the temperature. The infinite dilution apparent molar
expansibility, 􀜧φ
􀬴 , values for the binary systems (IL + methyl acetate or ethyl acetate or
methanol or ethanol) and (methanol + methyl acetate or ethyl acetate) and (ethanol + methyl
acetate or ethyl acetate) are positive and decrease with an increase in temperature due to the
solution volume increasing less rapidly than the pure solvent. For (IL + methyl acetate or
ethyl acetate or methanol or ethanol) systems 􀜧φ
􀬴 indicates that the interaction between (IL +
methyl acetate) is stronger than that of the (IL + ethanol) or (IL + methanol) or (IL + ethyl
acetate) solution. For the (methanol + methyl acetate or ethyl acetate) systems 􀜧φ
􀬴 values
vi
indicate that the interactions are stronger than (ethanol + methyl acetate or ethyl acetate)
systems.
Description: Submitted in fulfillment of the requirements of the Degree of Doctor of Technology: Chemistry, Durban University of Technology, 2010.
URI: http://hdl.handle.net/10321/559
Appears in Collections:Theses and dissertations (Applied Sciences)

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