Synergistic Enhancement of the Extraction and Separation Efficiencies of Lanthanoid(III) Ions by the Formation of Charged Adducts in an Ionic Liquid

Abstract

The synergistic ionic-liquid extraction and extraction equilibrium of lanthanoid(III) (Ln(III)) ions have been investigated using 2-thenoyltrifluoroacetone (Htta) and trioctylphosphine oxide (TOPO) in the ionic liquid 1-butyl-3methylimidazolium bis(trifluoromethanesulfonyl)imide ([C 4 mim][Tf 2 N]). The selective synergistic effect for heavier Ln(III) ions was found using a combination of Htta and TOPO in [C 4 mim][Tf 2 N], leading to enhanced separability among Ln(III) ions. The extracted Ln(III) species and the extraction constants in the Htta−TOPO system were determined by three-dimensional extraction equilibrium analysis. In this system, the neutral adduct, Ln(tta) 3 (TOPO) 2 , and the cationic charged adducts, Ln(tta) 2 (TOPO) 2 + , Ln(tta) 2 (TOPO) 3 + , and Ln(tta)(TOPO) 3 2+ , were extracted into the [C 4 mim][Tf 2 N] phase. The adduct formation constants in [C 4 mim][Tf 2 N] were determined to evaluate the synergistic effect of Htta and TOPO on the extraction of Ln(III) ions. The selective synergism for heavier Ln(III) ions in the Htta−TOPO system was ascribed to the formation of hydrophobic, charged adducts, such as Ln(tta) 2 (TOPO) 3 + and Ln(tta)(TOPO) 3 2+ , in [C 4 mim][Tf 2 N].

Extraction and Separation Factor for Lanthanum(III) and Cerium(III) Complexes from Aqueous Medium Using Ionic Liquid and Kerosene

“…Figure 2(a), the %E of Ce complex was higher than La(III) complex. [9]. Additionally, it was found that the separation of Lns(III) varied with the acidity of the β-diketones, for example, the SF between Eu(III) and Lu(III) in the synergistic system using benzoylacetone (Hba) with a higher pKa is significantly larger than those with the other β-diketones [11].…”

“…The synergistic extractability and the separation factor (SF) can be ascribed to the adduct formation of Ln(III)-β-diketones with neutral ligands in the organic phase and lowered with an increase in the atomic number of Ln(III) in the β-diketone-TOPO [9] [10]. Also, Okamura et al, found that the SF between La and Ce, Pr and Nd, Sm and Eu, and Eu and Gd with Htta and TOPO in [C 4 mim][Tf 2 N] is higher than that with D2EHPA or PC-88A in isooctane [9].…”

“…Some studies have used ILs as solvent of extraction of Ln(III). In the researches, highly selective synergism for the removal of lanthanoid(III) Ions with β-diketones and TOPO in an Ionic Liquid [9] [15]. Synergistic of the extraction and separation efficiencies of lanthanoid(III) Ions by forming charged adducts in an ionic liquid [9].…”

“…In the researches, highly selective synergism for the removal of lanthanoid(III) Ions with β-diketones and TOPO in an Ionic Liquid [9] [15]. Synergistic of the extraction and separation efficiencies of lanthanoid(III) Ions by forming charged adducts in an ionic liquid [9]. The cation and anion exchange mechanisms are specific to ILs extraction systems, often leading to improved extraction capacity and separability of Ln(III) and achieving competitive advantage results in VOCs [16] challenging goal in Lns(III) separation is to develop an effective process to improve separation and minimize environmental contamination.…”

“…pH meter. Previous studies have revealed that a high acidity in the aqueous solution results in an obvious decrease in the extraction efficiency of Lns(III)[9] [17] The removal extraction of La(III) and Ce(III) from the aqueous solutions was carried out by means of the same procedure reported in our previous work[18] [19]. The solvent extraction experiments were conducted by contacting 1 mL of aqueous solution with 1 mL of organic phase, where the phases were mixed in magnetic stirrers (SBS ® model ANS-001) at 140 rpm for 40 minutes at room temperature.…”