Electrochemical assessment of water|ionic liquid biphasic systems towards cesium extraction from nuclear waste

Abstract

A room temperature ionic liquid (IL) composed of a quaternary alkylphosphonium (trihexyltetradecylphosphonium, P66614(+)) and tetrakis(pentafluorophenyl)borate anion (TB(-)) was employed within a water|P66614TB (w|P66614TB or w|IL) biphasic system to evaluate cesium ion extraction in comparison to that with a traditional water|organic solvent (w|o) combination. (137)Cs is a major contributor to the radioactivity of spent nuclear fuel as it leaves the reactor, and its extraction efficiency is therefore of considerable importance. The extraction was facilitated by the ligand octyl(phenyl)-N,N'-diisobutylcarbamoylphosphine oxide (CMPO) used in TRans-Uranium EXtraction processes and investigated through well established liquid|liquid electrochemistry. This study gave access to the metal ion to ligand (1:n) stoichiometry and overall complexation constant, β, of the interfacial complexation reaction which were determined to be 1:3 and 1.6×10(11) at the w|P66614TB interface while the study at w|o elicited an n equal to 1 with β equal to 86.5. Through a straightforward relationship, these complexation constant values were converted to distribution coefficients, δ(α), with the ligand concentrations studied for comparison to other studies present in the literature; the w|o and w|IL systems gave δ(α) of 2 and 8.2×10(7), respectively, indicating a higher overall extraction efficiency for the latter. For the w|o system, the metal ion-ligand stoichiometries were confirmed through isotopic distribution analysis of mass spectra obtained by the direct injection of an emulsified water-organic solvent mixture into an electron spray ionization mass spectrometer.

Modulating the Solubilities of Ionic Liquid Components in Aqueous–Ionic Liquid Biphasic Systems: A Q‐NMR Investigation

“…In particular, in the field of metal extraction/separation/recycling by liquid/liquid processes, hydrophobic ILs of the type [C n C m im][Tf 2 N] (1-alkyl, 3-alkyl-imidazolium bis(trifluoromethylsulfonyl)imide) have already proved to be tremendously efficient media for a large variety of metals, [9] from Li + to Pu 4 + , [10,11] including d-elementATT="tptxpt=0mm tptxt=5mm tptxb=1.4mm"s [1,2,[11][12][13] and lanthanoids. [14][15][16][17][18][19] The huge potential that ILs present for extraction processes results from the complex extraction mechanisms, which are strongly dependent not only on the nature of the IL but also on the aqueous phase composition, [20] most often based on nitric or hydrochloAqueous-ionic liquid (A-IL) biphasic systems have been examined in terms of deuterated water, acid, and IL cation and anion mutual solubilities in the upper (water-rich, in mole fraction) and lower phase of aqueous/IL biphasic systems at ambient temperature.…”

Preparation and crystal structure of tetraoctylphosphonium tetrakis(pentafluorophenyl)borate ionic liquid for electrochemistry at its interface with water

“…ILs have been used in a wide variety of applications including battery electrolytes [4][5][6], solvent for nanoparticle synthesis [7], as antibacterial agents [8], etc. It has been shown that hydrophobic ILs are good candidates for metal ion extraction in biphasic, water|IL (w|IL) [9][10][11][12], systems. In metal ion extraction, a hydrophobic ligand is typically dissolved in the organic phase and coordinates with the metal ion either interfacially or in the bulk organic/aqeuous phase [13,14].…”

“…In metal ion extraction, a hydrophobic ligand is typically dissolved in the organic phase and coordinates with the metal ion either interfacially or in the bulk organic/aqeuous phase [13,14]. Conventional means of separation have been through physical mixing of the two phases [9,15]; however, as previously demonstrated [10][11][12]16], this process can also be investigated electrochemically using liquid|liquid electrochemistry performed at a polarizable interface between two immiscible electrolytic solutions (ITIES) [13,14,[17][18][19][20][21]. Furthermore, in order to reduce samples sizes and improve sensitivity, a micro-ITIES is often employed, such as at the tip of a pulled borosilicate glass capillary [11,16,[22][23][24].…”

Nanopipet-Based Liquid–Liquid Interface Probes for the Electrochemical Detection of Acetylcholine, Tryptamine, and Serotonin via Ionic Transfer

“…The use of pipet electrodes based on ionic transfer across an interface between two immiscible electrolyte solutions (ITIES) 28–41 has been an important method to detect ionic analytes. Ionic transfer of neurotransmitters across ITIES, mainly micro- and macrointerfaces has been reported.…”