Ion Specific Effects on the Mutual Solubilities of Water and Hydrophobic Ionic Liquids
authors Freire, MG; Carvalho, PJ; Silva, AMS; Santos, LMNBF; Rebelo, LPN; Marrucho, IM; Coutinho, JAP
nationality International
journal JOURNAL OF PHYSICAL CHEMISTRY B
keywords AQUEOUS BIPHASIC SYSTEMS; HYDROGEN-BOND STRUCTURE; LIQUID/ORGANIC MIXTURES; HOFMEISTER SERIES; PHASE-BEHAVIOR; SALTING-OUT; MECHANISM; MACROMOLECULES; PRECIPITATION; EXTRACTION
abstract Ion specific effects on the mutual solubilities between hydrophobic ionic liquids (ELs) and water are complex and not fully understood. The aim of this work is to obtain further evidence about the molecular mechanism behind this phenomenon by evaluating the effect of a large series of inorganic and organic salts on the mutual solubilities of water and the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(4)mim][Tf(2)N]. The magnitudes of the salting-in and salting-out effects were assessed by changing either the cation or the anion, in a series of salts, as well as the salt concentration. It was observed that the influence of the ions on the solubility followed the Hofmeister series. Both salting-in and salting-out effects were observed and they showed to be dependent on both the nature of the salt and its concentration, while the pH had only a marginal effect on the studied solubilities. On the basis of the solubility changes of the ionic liquid in water in the presence of salts and on NMR spectroscopic data, it will be shown that salting-out inducing ions (high charge density) and salting-in inducing ions (low charge density) act through different mechanisms. While the former act mainly through an entropic effect resulting from the formation of water-ion hydration complexes which cause the dehydration of the solute and the increase of the surface tension of the cavity, the salting-in results from a direct ion binding of the low charge density ions to the hydrophobic moieties of the solute.
publisher AMER CHEMICAL SOC
issn 1520-6106
year published 2009
volume 113
issue 1
beginning page 202
ending page 211
digital object identifier (doi) 10.1021/jp8080035
web of science category Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000262167800026
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journal analysis (jcr 2017):
journal impact factor 3.146
5 year journal impact factor 3.101
category normalized journal impact factor percentile 60.204
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