Diffusion coefficients and molar conductivities in aqueous solutions of 1-ethyl-3-methylimidazolium-based ionic liquids

Here, we presented new experimental data of diffusion coefficients of five [Emim, (1-ethyl-3-methylimidazolium)]-based ionic liquids in water at infinite dilution for temperatures ranging from 303.2 to 323.2 K using Taylor dispersion method. The investigated ILs were [Emim][C2N3 (dicyanamide)], [Emim][BF4 (tetrafluoroborate)], [Emim][C2H5SO4 (ethylsulfate)], [Emim][CF3SO3 (trifluoromethanesulfonate)], and [Emim][MDEGSO(4) (2-(2-methoxyethoxy) ethylsulfate)]. The molar conductivities of these ionic liquids were also measured and the infinite dilution conductances were calculated. The temperature dependency of the present experimental diffusion coefficients of the studied ionic liquids in water at infinite dilution were correlated using three equations; namely, Wilke-Chang, empirical (linear), and Nernst-Haskell equation. The Wilke-Chang equation underestimated the diffusion coefficient. The empirical, a typical linear fit, satisfactory represented the present measurements of all the studied systems. The Nernst-Haskell equation satisfactory predicted the diffusion coefficients of most of the ionic liquids under investigation. The self-diffusion coefficients of the studied ions at infinite dilution were also evaluated and briefly discussed. The present results could be very essential to the assessment of the impact of ionic liquid in the waste water stream since it is the most likely pollution it would contribute to the environment. (C) 2008 Elsevier B.V. All rights reserved.