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Aqueous Biphasic Systems with Ionic Liquids _________________________________________________________________________ 46 [IL] / (mol. kg -1 ) 7.0 6.0 5.0 4.0 3.0 2.0 1.0 Monophasic Region 0.0 0.0 0.5 1.0 1.5 2.0 2.5 [K3PO4] / (mol. kg-1 ) Figure 22. Phase diagrams for [C4mim]-based ternary systems composed by IL + K3PO4 + H2O at 298 K: , [C4mim][CF3SO3]; , [C4mim][N(CN)2]; □, [C4mim][HSO4];▲, [C4mim][TFA]; ×, [C4mim][Br]; ○, [C4mim][CH3SO3]; ▬ , [C4mim][Cl]; +, [C4mim][CH3CO2]. The results obtained show that the ability of ILs for ABS formation follows the order: [C2mim][CF3SO3] > [C2mim][EtSO4] > [C2mim][MeSO4] > [C2mim][Br] > [C2mim][Cl] [C2mim][CH3CO2] > [C2mim][CH3SO3] and [C4mim][CF3SO3] > [C4mim][N(CN)2] > [C4mim][HSO4] > [C4mim][TFA] > [C4mim][Br] > [C4mim][Cl] [C4mim][CH3CO2] [C4mim][CH3SO3]. In PEG-based ABS the salt anion has the major impact on the polymer solubility and hence in the ABS phase diagrams, while the cation has a minor (though sizeable) effect 74 . For the ILs, it is here shown that the IL cation has a huge influence in the phase diagrams behaviour allowing the IL-based ABS to be tailored to meet the specific requirements of a particular separation. Biphasic Region The salting-out effect is usually explained based on the ordering of bulk water and on the ability of the ions to decrease the water structure by a simple hydration phenomena. Recent
ILs + H2O + K3PO4 Ternary Systems _________________________________________________________________________ works are converging upon to the idea that interactions between the IL ions and the inorganic salt ions may be present, and are mainly responsible for the salting-in or salting- out phenomena 75, 76 . Salting-out inducing ions act mainly through an entropic effect resulting from the formation of water-ion hydration complexes while the salting-in inducing ions directly interact with the hydrophobic moieties of the IL. The ions specific effects seem to be dominated by the ion-ion versus ion-water interactions through a complex interplay of factors, and not by the water-structure modification as classically accepted 77 . Keeping in mind that PO4 3- is a high charge density ion (salting-out inducing ion), and that this ion was used in all the ternary systems evaluated, it is possible to assess the IL anions inducing character. According to Figure 21 and 22, the closer to the axis is located the binodal curve, the larger the IL anion salting-in inducing behaviour - that is the lower the density charge of the IL anions. Studies regarding the ILs polarity provide useful information on the IL cations and anions solvation at the molecular level. The introduction of empirical solvent polarity scales, based on solvent interactions with a reference solute, has lead to a rank on the compounds 78 . Frequently used polarity scales, based on solvatochromic probes, are the Reichardt ET(30) scale and the Kamlet-Taft’s solvent parameters 79, 80 . In fact, the polarities of imidazolium-based ILs were found to be similar to that of short chain alcohols 81 . A review regarding the polarity of ILs was recently published by Reichardt 82 . It should, nevertheless, be kept in mind that the solvent parameters are dependent on the molecule probe employed 79 , and particularly relevant for these nano-structured fluids. Table 6 reports the hydrogen bond basicity () and hydrogen bond acidity () of [C4mim]- based ILs using the solvatochromic probe [Fe(phen)2(CN)2]ClO4 83 . 47
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Catarina Maia Seco Seiça Neves Uni
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Ao meu Pai e ao meu Avô…
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agradecimentos Gostaria de começar
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keywords abstract Ionic liquids, wa
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4.2.3. Partitioning of L-tryptophan
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List of Abbreviations ABS Aqueous B
Page 21 and 22: List of Tables Table 1. Experimenta
Page 23 and 24: List of Figures Figure 1. Example o
Page 25 and 26: [C4mim][TFA]; ×, [C4mim][Br]; ○,
Page 27: 1. 1. General Introduction
Page 30 and 31: Aqueous Biphasic Systems with Ionic
Page 35 and 36: ILs + H2O Binary Systems __________
Page 41 and 42: Table 2. Experimental mole fraction
Page 49: 3. 3. QSPR Modelling of ILs + H2O B
Page 61 and 62: ILs + H2O + K3PO4 Ternary Systems _
Page 71: ILs + H2O + K3PO4 Ternary Systems _
Page 83: 5. 5. Final Remarks
Page 89 and 90: References ________________________
Page 95: 7. 7. List of Publications
Page 101 and 102: Appendix A ________________________
Page 111: Appendix B
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Aqueous Biphasic Systems with Ionic
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