Selective Extraction of Metal Ions from Aqueous Phase to Ionic Liquids: A Novel Thermodynamic Approach to Separations

Abstract

The selective extraction of metals from aqueous mixtures has generally relied on the use of selective ionophores. We present an alternative strategy that exploits a recently developed approach to extraction into an ionic liquid phase, and show that a high degree of control over selectivity can be obtained by tuning the relative concentrations of extraction agents. A thermodynamic model for the approach is presented, and an experimental separation of strontium and potassium ions is performed. It is shown that tuning the concentrations of the species involved can shift the ratio of potassium to strontium in the ionic liquid phase from 4:1 to 3:4. This extraction is performed under mild conditions with relatively common reagents. The result is a proof-of-concept for a novel separations scheme that could have great importance in a wide range of technological applications.

Copper extraction using protic ionic liquids: Evidence of the Hofmeister effect

“…The observed anion:copper ratios do not necessarily indicate that the anions are coordinated with the copper, as previous work indicates that charged metal complexes are soluble in ILs [14,15] and uncoordinated ions can move into the IL phase in tandem with a charged metal complex to maintain electroneutrality [59,60]. As indicated in Table 3, all three mineral anions used in the present study coordinate relatively weakly with copper(II).…”

“…Ion exchange mechanisms involving metals and IL cations have been studied extensively [55][56][57][58][59][60], and it is observed that strongly hydrophobic cations such as 1-decyl-3-methylimidazolium generally do not undergo extensive ion exchange [61]. The trialkylammonium species in the ILs used in the current study are sufficiently hydrophobic that it would be quite surprising if they engaged in ion exchange to a significant degree.…”

Electrodeposition of metal cations from the wet ionic liquid [EMIM][TFSI]

“…Although not examined experimentally in this work, the literature on electrodeposition of metals from anhydrous ILs [23][24][25][26] suggests that this should be a general phenomenon. More particularly, if this approach should be developed into a technology, we would use cation-selective ILs [27][28][29][30][31][32][33]…”

Liquid‐ and Solid‐based Separations Employing Ionic Liquids for the Recovery of Platinum Group Metals Typically Encountered in Catalytic Converters: A Review

“…An excellent discussion on the topic of metal extraction to ILs is available in the literature by Janssen et al [111] The experimental works of Dietz et al, [117,118] Jensen et al, [119,120] Visser et al, [121,122] and Janssen et al [123,124] definitely deserve attention and can provide a profound insight on the mechanistic processes, while a thermodynamic perspective on the topic has been provided by Kobrak. [125] A detailed discussion of all mechanistic considerations is not within the scope of the present review; thus, we strongly encourage the readers to refer to the works cited above to get a deeper understanding of the quite complicated but very interesting topic of extraction mechanisms.…”

“…An excellent discussion on the topic of metal extraction to ILs is available in the literature by Janssen et al [111] . The experimental works of Dietz et al., [117,118] Jensen et al., [119,120] Visser et al., [121,122] and Janssen et al [123,124] . definitely deserve attention and can provide a profound insight on the mechanistic processes, while a thermodynamic perspective on the topic has been provided by Kobrak [125] .…”