Ionic‐Liquid‐Based Acidic Aqueous Biphasic Systems for Simultaneous Leaching and Extraction of Metallic Ions

Abstract

The first instance of an acidic aqueous biphasic system (AcABS) based on tributyltetradecyl phosphonium chloride ([P ][Cl]) and an acid is here reported. This AcABS exhibits pronounced thermomorphic behavior and is shown to be applicable to the extraction of metal ions from concentrated acidic solutions. Metal ions such as cobalt(II), iron(III), platinum(IV) and nickel(II) are found to partition preferentially to one of the phases of the acidic aqueous biphasic system and it is here shown that it successfully allows the difficult separation of Co from Ni , here studied at 24 and 50 °C.

Metal Extraction with Ionic Liquids-Based Aqueous Two-Phase System

“…Mixtures containing 17.8% IL, 25.9% HCl, 56.3% H 2 O and 18.1% IL, 20.8% HCl and 61.1% H 2 O at 50°C yielded a nearly pure Co(II) in the IL-rich phase, with a separation factor of 400 and 376, respectively. These promising results demonstrate that an acidic aqueous biphasic system can be used simply and efficiently for the critical separation of Co (II) and Ni (II) directly from the HCl leachates of NiMH batteries [39].…”

“…Some ILs that form a homogeneous phase below the critical solution temperature were also applied in metal ion separation. Gras et al [39] reported the formation of a two-phase system by mixing concentrated hydrochloric acid with tributyl(tetradecyl) phosphonium chloride ([P 44414 ][Cl]), which is water miscible below the critical solution temperature. The use of concentrated hydrochloric acid allows for the simultaneous leaching and extraction of metal ions.…”

A Comparison of Cobalt and Platinum Extraction in Hydrophobic and Hydrophilic Ionic Liquids: Implication for Proton Exchange Membrane Fuel Cell Recycling

“…5either through ion-pair or anion-exchange reaction: Due to the sole presence of Pt(IV) as PtCl 6 2in the studied HCl concentration range, Pt(IV) extraction proceeds exclusively by anion exchange according to equation 7 HCl, CoCl 3as the predominant cobalt species in solution is then gradually replaced by the more charge dense CoCl 4 2at higher concentrations of HCl. 8,21,22,[36][37][38][39][40] However, as the listed HCl concentration corresponds to that of the initial aqueous phase concentration before addition of the IL, the total system chloride concentration is in fact diluted when considering the total system volume. As such, extraction most likely proceeds via an ion-pairing mechanism, equation 6, and the extraction of the CoCl 2 species to the IL phase in accordance with that found for Co(II) partition from chloride media with other basic extractants.…”

“…3,[18][19][20] Our group recently proposed a new acidic ABS (AcABS) that overcomes the presented limitations of ABS at the low pH typical of common leach solutions. 21 In AcABS, a suitable hydrophilic IL is salted-out by the acid inherently present in the leach solution, allowing for the design of an integrated platform for a "one-pot" hydrometallurgical treatment. Compared to the studies using neutral ABS for metal extraction, 22 AcABS avoid metal hydrolysis, a crucial factor for the extraction of certain metal such as platinum.…”

Chasing Aqueous Biphasic Systems from Simple Salts by Exploring the LiTFSI/LiCl/H2O Phase Diagram

“…This fact has long been exploited, e.g., for the separation of aqueous solutes via liquid–liquid extraction using organic phases or ionic liquids. 5−7 While the first ABSs based on polymers were discovered in the late 19th century, 8 the coexistence of two aqueous solutions of different salts has been reported only much more recently and the range of such ABSs remains comparatively limited. 9−11 Their composition usually involves a concentrated inorganic salt and an ionic liquid.…”