Apparent molar properties of trioctylmethylammonium based ionic liquids in toluene and dodecane at T = (293.15 to 328.15) K

Abstract

The structural variance ability of ionic liquids (ILs) provides an opportunity to fine tune the thermophysical properties for given application. For effective extraction of metal ion from water, the applied ILs should be hydrophobic and preferably containing non fluorinated anions. The hydrophobicity of ILs can be further manipulated by the addition of diluents. To understand extraction of metal ion using binary mixtures of ILs + diluent, it is utmost important to explore different types of interactions exist in the binary mixtures using thermophysical properties. For this purpose, we present experimentally measured data of densities, ρ and speeds of sound, u for binary solutions of aprotic ionic liquids (APILs) namely trioctylmethylammonioum bis-(2-ethylhexyl) phosphate [TOMA][DEHP], trioctylmethylammonioum bis-(2-ethylhexyl) diglycolamate [TOMA][DGA], trioctylmethylammonioum bis-(2-ethyhexyl)sulfosuccinate [TOMA][DEHS] in toluene and dodecane (diluents) at T = 293.15 K to 328.15 K. The apparent molar properties like volume Vϕ, isentropic compressibility Ks,ϕ and limiting expansivity Eϕ∞ were calculated and explained in terms of temperature, size of anion, and nature of solvent. The both Vϕ and Ks,ϕ were increased with rise in temperature and replacing toluene with dodecane whereas decreased with increase in concentration of APIL. The Redlich-Mayer type equation was used to correlate apparent molar volume, Vϕ∞ and apparent molar isentropic compressibility, Kϕ∞ at infinite dilution. The influence of interactions (IL-IL or IL-solvent) in studied binary mixtures was elucidated by Sv and Sk parameters. It was observed that ion-solvent interactions are dominating in APILs + toluene than in APILs + dodecane.