Extraction of Uranium and Thorium from Nitric Acid Solution by TODGA in Ionic Liquids

Advanced Uranium Removal with Pure, Nonfluorinated Ionic Liquids: Fine-Tuning Hydrophilic and Hydrophobic Properties for Enhanced Selectivity

Ionic liquids (ILs) have significant potential for eco-friendly extraction of uranium from aqueous solutions, which is critical for nuclear technology, fuel cycle management, and environmental protection. This study examines the impact of the adjustable hydrophobic/hydrophilic properties of ILs on the removal of uranium(VI) (UO22+) from aqueous solutions utilizing both a novel hydrophilic IL (1-butoxyethyl-1-methylmorpholinium butoxyethylphosphite - Mor1-2O4-BOEP) and 1-heptyl-1-methylmorpholinium heptylphosphite (Mor1-7-HP) as an example of a hydrophobic IL with a similar structure. The transfer mechanism of uranyl ions from water to organic or solid phases closely depends on the physicochemical properties of ILs, especially their hydrophobicity. The hydrophobic Mor1-7-HP extracts uranyl via neutral complex formation as UO2(NO3)2-(Mor1-7-HP)2. Conversely, hydrophilic Mor1-2O4-BOEP induced selective precipitation as UO2(NO3)-(BOEP), transferring uranyl to the solid phase. Optimization of the working parameters, in terms of acidity of the aqueous solution and amount of ILs used, allowed the extraction of over 98% of U(VI). The stoichiometry of the organic complex and the precipitate was determined using physicochemical techniques. These tunable H-phosphonate-based ILs have advantages over traditional solvent extraction and conventional ILs, allowing easier handling, improved selectivity, and lower environmental impact. This work advances uranium separation techniques with applications in hydrometallurgy, particularly in the treatment of wastewater and radioactive waste for sustainable uranium recovery.

Substituent Effect on the Selective Separation and Complexation of Trivalent Americium and Lanthanides by N,O-Hybrid 2,9-Diamide-1,10-phenanthroline Ligands in Ionic Liquid

The extraction and complexation of trivalent americium (Am) and lanthanides (Ln) by four 2,9-diamide-1,10-phenanthroline (DAPhen) ligands with different alkyl substituent groups on the diamide moiety in an ionic liquid (IL), C₄mimNTf₂, were studied through a combination of batch extraction, spectroscopic, and calorimetric approaches. All four DAPhen ligands can achieve selective separation of Am(III) from Eu(III), but the detailed extractability and the extraction kinetics are affected significantly by the length of the alkyl substituent groups. UV-vis absorption spectrophotometric titrations indicate that Ln(III) coordinates with all four ligands in a 1:2 mode in the ionic liquid and the binding strength decreases with the increase of the alkyl chain length. The complexation of the DAPhen ligands with Ln(III) in the ionic liquid is driven by highly positive entropies and opposed by endothermic enthalpies. A luminescence spectroscopy study suggests that each DAPhen ligand coordinates in a tetradentate form with Eu(III). This work further unravels the unique extraction and coordination behavior in an ionic liquid system and offers additional guidelines to design more efficient DAPhen ligands for Ln(III)/An(III) separation.

Phosphate-Based Ultrahigh Molecular Weight Polyethylene Fibers for Efficient Removal of Uranium from Carbonate Solution Containing Fluoride Ions

This work provides a cost-effective approach for preparing functional polymeric fibers used for removing uranium (U(VI)) from carbonate solution containing NaF. Phosphate-based ultrahigh molecular weight polyethylene (UHMWPE-g-PO₄) fibers were developed by grafting of glycidyl methacrylate, and ring-opening reaction using phosphoric acid. Uranium (U(VI)) adsorption capacity of UHMWPE-g-PO₄ fibers was dependent on the density of phosphate groups (DPO, mmol∙g−1). UHMWPE-g-PO₄ fibers with a DPO of 2.01 mmol∙g−1 removed 99.5% of U(VI) from a Na₂CO₃ solution without the presence of NaF. In addition, when NaF concentration was 3 g∙L−1, 150 times larger than that of U(VI), the U(VI) removal ratio was still able to reach 92%. The adsorption process was proved to follow pseudo-second-order kinetics and Langmuir isotherm model. The experimental maximum U(VI) adsorption capacity (Qmax) of UHMWPE-g-PO₄ fibers reached 110.7 mg∙g−1, which is close to the calculated Qmax (117.1 mg∙g−1) by Langmuir equation. Compared to F−, Cl−, NO₃−, and SO₄²− did not influence U(VI) removal ratio, but, H₂PO₄− and CO₃²− significantly reduced U(VI) removal ratio in the order of F− > H₂PO₄− > CO₃²−. Cyclic U(VI) sorption-desorption tests suggested that UHMWPE-g-PO₄ fibers were reusable. These results support that UHMWPE-g-PO₄ fibers can efficiently remove U(VI) from carbonate solutions containing NaF.

Fast selective homogeneous extraction of UO22+ with carboxyl-functionalised task-specific ionic liquids

The carboxyl-functionalised task-specific ionic liquid of 1-carboxymethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide ([HOOCmim][NTf₂]) was used as solvent and extractant for UO₂²⁺ extraction from aqueous solution. A homogeneous phase of [HOOCmim][NTf₂]-H₂O system could be achieved at 75 °C, and 86.8 ± 4.8% of UO₂²⁺ was separated from the aqueous solution after vibrating for only 1 min. Furthermore, nearly 97.3 ± 2.9% of UO₂²⁺ was stripped from [HOOCmim][NTf₂] phase by 1 M HNO₃ solution. K⁺, Na⁺, Mg²⁺, Dy³⁺, La³⁺, and Eu³⁺ have little influence on the homogeneous extraction of UO₂²⁺, and the extraction efficiency of UO₂²⁺ still remained at ca. 80%. Experimental and theoretical study on the selectivity of [HOOCmim][NTf₂]-H₂O system were performed for the first time. Density functional theory calculation indicates that the solvent effect plays a significant role on the selectivity of [HOOCmim][NTf₂]-H₂O.

Diglycolamide-Based Solvent Systems in Room Temperature Ionic Liquids for Actinide Ion Extraction: A Review

This review article gives a comprehensive account of the extraction of actinide ions using room temperature ionic liquid-based solvent systems containing diglycolamide (DGA) or functionalized DGA extractants. These extractants include multiple DGA-functionalized ligands such as tripodal DGA (T-DGA) and DGA-functionalized calix [4]arenes (C4DGA). Apart from metal ion extraction behaviour, other important features of the ionic liquid-based solvent systems such as separation behaviour, luminescence spectroscopic results, thermodynamics of extraction and radiolytic stability of the ionic liquid-based solvents are also reviewed. Results from studies on DGA-functionalized task-specific ionic liquids (TSIL) are also included in this review article.