Homogenous Liquid–Liquid Extraction of Au(III) from Acidic Medium by Ionic Liquid Thermomorphic Systems

Abstract

Two ionic liquid (IL) thermomorphic systems were designed. The thermoregulated property exhibited by the IL systems was utilized for the recovery of Au­(III) from acidic medium. The cloud point order of the two ILs was proposed and evidenced via a combination of experimental measurements and quantum chemical calculations. The impacts of salt ions and acid on the thermomorphic phase behavior of the IL–H2O binary mixture system were investigated. After comprehensive comparison, a systematic study of Au­(III) extraction by the [Suc]­[Tf2N]2 (succinyl bis­(trifluoromethylsulfonyl)­imide) system was carried out because of its outstanding hydrophobicity and extraction ability. Then, a comparison between traditional liquid–liquid extraction (TLLE) and homogeneous liquid–liquid extraction (HLLE) was made during the process of optimization of various extraction parameters. In addition, the anion-exchange mechanism in the extraction process was revealed. The thermoregulated [Suc]­[Tf2N]2 system presented an excellent selectivity for Au­(III) in a solution of coexisting multimetallic ions. Finally, Au­(III) was almost completely stripped from the loaded IL phase by oxalic acid. The extraction efficiency of Au­(III) using regenerated IL still maintains a surprising stability after five turns of cycling experiments. Hence, the dicationic IL [Suc]­[Tf2N]2 was regarded as a potential extractant for the recovery of gold.

Sensing vs Extraction: Functionalized Ionic Liquid as a Single Platform for Dual Applications with Biological Implications

“…Later on, Davis and co-workers introduced the concept of tailored-made functionalized ionic liquids or task-specific ionic liquids (TSILs), where they made receptors an intrinsic part of ionic liquids for specific functions. − Since then, the TSILs have attracted the notice of many researchers around the globe for various applications. − Furthermore, Rogers and co-workers have demonstrated that binary mixtures of TSILs and less expensive hydrophobic ILs can be used as the extracting phase . Though ionic liquids are well explored as a better partitioning media for extraction studies, − relatively less explored for sensing studies − but rarely explored for dual functional studies. , Though these early reports were impressive, but the fluorescence sensing studies were carried out in a nonaqueous medium using hydrophobic TSILs, which do not represent a true sensory system. However, a proper sensory probe should be water-soluble.…”

Selective and Efficient Gold Extraction from E-Waste by Pyrrolidinium-Based Ionic Liquids with Various N-Substituents

“…The order of the maximum extraction capacities of the three pyrrolidinium-based ILs with different N-substituents for Au­(III) is [Pyr-EA]­[NTf 2 ] (524.6 mg·g –1 ) > [Pyr-Bu]­[NTf 2 ] (457.3 mg·g –1 ) > [Pyr-C 2 OC 2 ]­[NTf 2 ] (403.5 mg·g –1 ). In particular, as shown in Figure (B), [Pyr-EA]­[NTf 2 ] possesses a superior maximum capacity when compared to most ILs and non-IL based methods reported in the literature, ,− indicating that [Pyr-EA]­[NTf 2 ] is an effective extractant for Au­(III).…”

“…As displayed in Figure (C), compared with pure ILs, the signal peak at 120 ppm in the extracted species disappeared, while the chemical shifts of other peaks remained basically unchanged. In particular, the peak at 120 ppm belongs to −CF 3 of NTf 2 – . It indicates that the NTf 2 – anions of ILs are transferred to the water phase during extraction.…”

“…RT K H T S ln ex (10) The thermodynamics parameters are given in Table S3. The ΔH θ is −27.766 kJ•mol −1 , indicating that the extraction process is exothermic.…”

“…In recent years, ILs have become alternatives to traditional organic solvents and extractants, which have attracted more and more attention in the field of metal extraction because of their “green” and “structure-tunability” properties . Especially, imidazole-based, quaternary ammonium-based, pyridine-based, and quaternary phosphonium-based ILs show excellent extraction efficiency in Au­(III). − However, most ILs have very high viscosities, which lead to slow mass transfer, heavy dependence on organic solvents, and difficult phase separation. The above problems greatly limit the industrial applications of ILs.…”