Aqueous-ionic liquid (A-IL) biphasic systems containing deuterated water, deuterated nitric acid (10 À2 M to 7 M) and either [C 1 C 4 im + ][Tf 2 N À ], [C 1 C 10 im + ][Tf 2 N À ] or [Me 3 BuN + ][Tf 2 N À ] have been examined in terms of water and acid solubilities in the IL-rich phase and in terms of IL cation and anion solubilities in the waterrich phase. Other experiments focused on the IL cation and anion solubility in the water-rich phase upon addition of either [C 1 C 4 im + ][Cl À ] or [Li + ][Tf 2 N À ]. The results evidence a complex interplay between all negatively and positively charged ions of the samples that could be described following the usual approach used for aqueous-aqueous (A-A) biphasic systems. Other examples from the literature are discussed and demonstrate that the frontier between A-A and A-IL systems is questionable. Predictions are made for the extraction of metallic ions by use of biphasic systems in this work that are successfully compared to literature data.

We have studied the extraction of four HA acids (HNO(3), HReO(4), HClO(4), HCl) to a hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium-bis(trifluoromethanesulfonyl)amide (BMI(+) Tf(2)N(-)) at room temperature, in a wide range of acidic concentrations in water. The effect of tributylphosphate (TBP) as co-solvent is investigated. According to experimental observations, water dragging to the IL phase increases with added TBP and/or acids. Acid extraction is found to be weak, however, for the four acids except for concentrated HNO(3) (>3 M). Molecular dynamics simulations on model biphasic systems show that TBP is not surface active, but well dissolved in the IL. They also reveal the importance of HA acid model (either totally or half dissociated) and of the TBP content on acid extraction to the IL. Furthermore, they show that "the proton" can be extracted by TBP (H(3)O(+)(TBP)(3)"complex") without its A(-) conjugated base, via a cation transfer mechanism (BMI(+) transfer to water). Experiments and simulations show that TBP plays an important role in the mutual solubility between water and ionic liquid, by different amounts, depending on the HA acid. On the other hand, both approaches indicate that a HTf(2)N containing aqueous solution completely mixes with the [BMI][Tf(2)N] IL that contains the same Tf(2)N(-) anion.

The extraction of uranyl from acidic (HNO(3)) aqueous solutions toward an ionic liquid phase, C(1)-C(4)-imTf(2)N (1-methyl,3-butylimidazolium Tf(2)N), has been investigated as a function of initial acid concentration and ligand concentration for two different extracting moieties: a classical malonamide, N,N'-dimethyl-N,N'-dibutylmalonamide (DMDBMA) and a functionalized IL composed of the Tf(2)N(-) anion and an imidazolium cation on which a malonamide pattern has been grafted (FIL-MA). The extraction mechanism, as demonstrated through the influence of added C(1)-C(4)-imCl or added LiTf(2)N in the aqueous phase, is slightly different between the DMDBMA and FIL-MA extracting agents. Modeling of the extraction data evidences a double extraction mechanism, with cation exchange of UO(2)(2+)versus 2 H(+) for DMDBMA or versus C(1)-C(4) -im(+) and H(+) for FIL-MA at low acidic values, and through anion exchange of [UO(2)(NO(3))(3)](-)versus Tf(2)N(-) for both ligands at high HNO(3) concentrations. The FIL-MA molecule is more efficient than its classical DMDBMA parent.

Previous studies have shown that the presence of nitric acid, the principal solute in various hydrometallurgical processes, and perchloric acid in the aqueous phase is an important factor for increased aqueous solubility of hydrophobic ionic liquids. In this study, the effect of hydrochloric acid in the aqueous phase on the mutual solubility of water and hydrophobic 1,3-dialkylimidazolium-and N,Ndialkylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids, [C n mim][Tf 2 N] (n ¼ 2, 4, 6, and 8) and [C 3 C 1 pyrr][Tf 2 N], is examined at room temperature and atmospheric pressure. Hydrochloric acid caused a considerable increase in the aqueous solubility of all the studied ionic liquids. The amount of water transferred into the organic phase increases with increasing hydrochloric acid concentration for short alkyl chain ILs, and the opposite trend was observed for long alkyl chain ILs. The effect of the N-H acid bis(trifluoromethylsulfonyl)imide, H[Tf 2 N], and the salts lithium bis(trifluoromethylsulfonyl)imide, Li[Tf 2 N], and 1-butyl-3-methylimidazolium chloride, [C 4 mim]Cl, dissolved in hydrochloric acid solutions on the mutual solubility of water and the [C 4 mim][Tf 2 N] ionic liquid were also investigated. The salting-out effect is observed and it was shown to be dependent on the nature of the salt, its concentration and the hydrochloric acid concentration in the aqueous phase. A mathematical model has been developed to describe the dependence of the ionic liquid cation and anion concentration on the common ion salt concentration in the aqueous hydrochloric acid phase. This model describes the basic character of ionic liquid dissolution in the aqueous phase and allows for estimation of solubility product values.