Solvent Extraction in Analytical Separation Techniques

Abstract

1345Solvent extraction is one of the most effective analytical methods for the separation, purification, and removal of target metal ions (e.g. valuable metal ions, toxic metal ions and radioactive fission products) from aqueous solutions containing various metal ions. This technique has been widely used in many areas of chemistry, not only for the separation analysis of trace elements, but also for hydrometallurgy, metal recycling, and nuclear fuel processing. 1,2 Novel extractants and a synergistic extraction system have been developed to improve the extraction performance and separation ability for metal ions. Suzuki et al. reported on the separation of Am(III) and Eu(III) using an alkyldiamideaminetype extractant (ADAAM), which is a tridentate ligand composed of one soft N-donor atom and two hard O-donor atoms. 3 ADAAM showed a high extraction performance and selectivity for Am(III) over Eu(III) from a highly acidic solution, yielding a high separation factor of around 25. The authors assumed that the extraction behavior can be attributed to a combination effect between the coordination ability of two hard amide C=O donor groups for f-elements and the selectivity of one soft N-donor atom for Am(III). In addition, the authors reported continuously on the mutual separation of Am(III) and Cm(III) using ADAAM as an extractant and water-soluble diglycolamide ligand as a masking agent. 4 This combination provided high selectivity for Am(III) over Cm(III) with separation factors of up to 41. Narita et al. investigated the extraction behavior of Pd(II) from HCl and HBr solutions using N,N,N′,N′-tetra-2-ethylhexylthioglycol amide (TEHTDGA), which was compared with an extraction system using the conventional extractant, di-n-hexyl sulfide (DHS). 5 In the TEHTDGA system, the extractability of Pd(II) from a HBr solution was inferior to that from a HCl solution, which is opposite to the extraction behavior observed in the DHS system.FT-IR spectroscopy and EXAFS measurements indicated that the inner-sphere structure of Pd(II)-TEHTDGA complexes was almost the same as that of Pd(II)-DHS complexes in both cases of HCl and HBr solutions: two sulfur atoms directly coordinated to the Pd(II) ion by replacing two halide ions. Katsuta et al. reported on the extraction of Li + and Na + with a metallacrown in the presence of organic dye anions. 6 This system enabled selective Li + extraction and a spectrophotometric determination of Li + at the sub ppm level in seawater. Onizaki et al. developed a synergistic extraction system of Sr(II) using tri-n-octylphosphine oxide (TOPO) and dicyclohexano-18-crown-6 (DC18C6) in the presence of the bis(trifluoromethanesulfonyl)imide anion (Tf2N -). 7 The authors demonstrated that the co-use of TOPO and DC18C6 drastically enhanced the extraction efficiency more than the sum of the extraction by the individual extractants based on additional formation concerning Sr(DC18C6)(TOPO) 2+ ·2Tf2Nand Sr(DC18C6)(TOPO)2 2+ ·2Tf2N -.Recently, ionic liquids (ILs) 8 and deep eutectic solvents (DESs) 9 have attra...

Relative distribution enhancement: a new factor for the evaluation of synergistic solvent extraction

“…Solvent extraction (SX), or liquid–liquid extraction, is considered an effective process, widely used for separation, purification and extraction at the laboratory and industrial scale. SX is extensively used in many industries such as petroleum, chemistry, biochemistry, food, hydrometallurgy, metal recycling and nuclear fuel processing 1,2 …”

“…SX is a separation operation by phase addition that relies on selecting the phase to be added for successful extraction. Reagents used for metal extraction purposes can be broadly classified into three major types: 1 solvating extractants (or neutral), 2 anion‐exchanging extractants (or basic), and 3 cation‐exchanging extractants. The last type can also be subdivided into acidic and chelating extractants 3,4 .…”

“…SX is extensively used in many industries such as petroleum, chemistry, biochemistry, food, hydrometallurgy, metal recycling and nuclear fuel processing. 1,2 SX is a separation operation by phase addition that relies on selecting the phase to be added for successful extraction. Reagents used for metal extraction purposes can be broadly classified into three major types: 1 solvating extractants (or neutral), 2 anion-exchanging extractants (or basic), and 3 cation-exchanging extractants.…”

Recent Progress in Ionic Liquid Extraction for the Separation of Rare Earth Elements

“…Solvent extraction, or liquid-liquid extraction, is among the most promising techniques for recovering and separating metal ions, [8][9][10] including REEs. 11,12 This technique has been broadly employed in many fields, including hydrometallurgy, analytical chemistry, and nuclear fuel reprocessing.…”

Enzyme-responsive Fluorescent Ionic Liquid

“…Thus, ILs have been utilized as functional sensor materials in the field of analytical chemistry. [21][22][23][24] Recently, our group developed a plasticizer-free PVC membrane, which was composed of an ionic liquid-based dye (IL-Dye) in order to overcome a limitation of the dye solubility in the PVC membrane. [25][26][27] The IL-Dye serves dual functions of a lipophilic pH indicator dye (chromophore) and a plasticizer.…”