Mutual solubility of water and hydrophobic ionic liquids in the presence of hydrochloric acid

Abstract

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.

Development and Application of Supported Ionic Liquid Membranes in Microbial Fuel Cell Technology: A Concise Overview

“…By taking into account the contribution of various ions to the salting-out of IL from water, it can be said that an MFC operation at elevated H 2 PO 4 − , PO 4 3− , and SO 4 2− concentrations (100-200 mM) may be feasible and advantageous, while higher Na + , K + , Ca 2+ , and Mg 2+ concentrations may suppress the solubility of water in the IL phase (although, this latter aspect shows less significance) [53,56]. In addition, it can be said that high amounts of H + and NH 4 + should be avoided, as these compounds may effectively contribute to the increased mutual solubility of IL and water [53,57].…”

“…This mechanism may be of interest for MFCs in terms of anodic organic compounds (as agents interfering with the cathode-surface reactions due to crossover), including substrates. It is also important to note that the presence of various ions in aqueous media may alter the mutual solubility of water and IL [53,57].…”

A general environmentally friendly access to long chain fatty acid ionic liquids (LCFA-ILs)

“…Usually, for petroleum-based hydrophobic ILs, the properties can be tuned by changing the cation substituent(s) and the anion identity: for example, highly fluorinated anions give hydrophobic salts with remarkable physico-chemical properties (low viscosity, high conductivity and so on). [26][27][28][29] For LCFA-ILs, the major effect comes from the fatty acid anion alkyl chain length and degree of saturation. LCFA-ILs have been tested as green alternatives to the conventional hydrophobic ILs in liquid-liquid extraction, demonstrating their capability to extract metals [18,23] and phenols [22] from aqueous solutions.…”

Selective Liquid‐Liquid Extraction of Uranium by Phosphoramidate‐Group Bearing Ionic Liquid

“…The synthesized TSIL (viscosity; η determined =2836±8 cP at 298 K) being highly viscous has been diluted in 1‐Butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ([C 4 mim][NTf 2 ]; η reported =50.34 cP at 298 K) medium and then used in LLE procedure. The diluent ionic liquid viz., [C 4 mim][NTf 2 ] has been choosen by considering its chemical stability towards concentrated HNO 3 medium, very low viscosity compared to the TSIL, low water solubility and α and γ radiation stability . Increase or decrease in the alkyl chain length or branching of the cationic part of this ionic liquid would result in either higher viscosity or higher water solubility.…”