Hydrophobic Deep Eutectic Solvents Incorporating Trioctylphosphine Oxide: Advanced Liquid Extractants

Abstract

A low viscosity, hydrophobic eutectic solvent based on trioctylphosphine oxide (TOPO) has been developed and characterized, and its use as an extractant demonstrated for liquid−liquid separation of uranyl nitrate from aqueous acid. This strategy of liquefying the active extracting agent as a eutectic liquid produced liquids that contain an intrinsically high concentration of TOPO (ca. 80 wt %, 1.875 mol L −1 at χ TOPO = 0.50) and renders the use of an organic (hydrocarbon) diluent redundant.

Recent Advances in Hydrophobic Deep Eutectic Solvents for Extraction

“…Additionally, selecting the appropriate pH, HDES type, and extraction time and type is important to enhance yield. Another liquid-liquid extraction of metal uranyl nitrate ([UO2] 2+ ) from aqueous acid using low viscous hydrophobic eutectic solvent from trioctylphosphine and phenol has been reported [65]. The presence of phenol in the mixture was crucial for generating the eutectic mixture composition rather than having a role in the uranyl complexation and extraction [65].…”

“…Another liquid-liquid extraction of metal uranyl nitrate ([UO2] 2+ ) from aqueous acid using low viscous hydrophobic eutectic solvent from trioctylphosphine and phenol has been reported [65]. The presence of phenol in the mixture was crucial for generating the eutectic mixture composition rather than having a role in the uranyl complexation and extraction [65]. The thermal stability of the trioctylphosphine, phenol HDES mixture, which is defined by the loss of phenol from the liquid, is between 90-100 • C.…”

Hydrophobic Deep Eutectic Solvents for the Recovery of Bio-Based Chemicals: Solid–Liquid Equilibria and Liquid–Liquid Extraction

“…This makes many DESs quite hygroscopic [43], and this limits their applicability in biorefinery applications where aqueous streams are common. Hence, hydrophobic DESs were sought after when extractions from aqueous streams are aimed at and found by, among others, van Osch et al [44], who used high-molecular weight carboxylic acids; Gilmore et al [45] and Schaeffer et al [46], who used trioctylphosphine oxide (TOPO); Cañadas et al [47] who used high-molecular amines; and Abranches et al [48], who demonstrated an unusually strong interaction between aromatic and aliphatic hydroxyl groups and defined this as a type V non-ionic DES. The hydrophobic DESs described by van Osch et al [44] have been studied in liquid-liquid extractions [44,49,50], and hydrophobic DESs, in general, have been applied to remove riboflavin [51], chlorophenols [52], caffeine [53], tryptophan [53], vanillin [53], isophthalic acid [53], platinum group and transition metals [45,46], phenolic antioxidants [47], and polycyclic aromatic hydrocarbons [54] from water.…”

Probing a variation of the inverse-trans-influence in americium and lanthanide tribromide tris(tricyclohexylphosphine oxide) complexes

“…Phosphine oxides are highly stable ligands that have been utilized primarily for catalysis on elements across the periodic table. 1 The study of phosphine oxides with f-elements has primarily focused on their use in extraction processes [2][3][4][5] and in (pseudo)halide/nitrate f-element starting materials. [6][7][8][9] The effect of two ligands trans to one another is most prototypically examined in the actinyls, AnO 2 n+ , where the trans-oxygens display unusually short bond distances and high bond strength, best described as bond order of three.…”