Insights into the Mechanism of Extraction of Uranium (VI) from Nitric Acid Solution into an Ionic Liquid by using Tri-n-butyl phosphate

Solvent extraction of rare earths elements from nitrate media in DMDOHEMA/ionic liquid systems: performance and mechanism studies

Extraction of La(iii), Eu(iii) and Fe(iii) was compared in n-dodecane and two ionic liquids (ILs) (1-ethyl-1-butylpiperidinium bis (trifluoromethylsulfonyl)imide [EBPip⁺] [NTf₂⁻] and 1-ethyl-1-octylpiperidinium bis (trifluoromethylsulfonyl)imide [EOPip⁺] [NTf₂⁻]). Using the extractant N,N′-dimethyl-N,N′-dioctylhexylethoxymalonamide (DMDOHEMA), the effect of pH was investigated in detail to recover extraction mechanisms. The use of ILs as the organic solvent instead of n-dodecane, greatly enhances extraction efficiency, and an ionic liquid with a shorter alkyl chain [EBPip⁺] [NTf₂⁻] provides higher extraction than [EOPip⁺] [NTf₂⁻]. The mechanistic study points out that for low nitric acid concentrations ([HNO₃] ≤ 0.01 M), metal is extracted via a cation of the ionic liquids, while for higher nitric acid concentrations ([HNO₃] ≥ 1.0 M), extraction occurs through pure solvation mechanism of DMDOHEMA as in conventional diluents. This latter case is of high interest for applications, as higher extraction can be obtained without any loss of ILs by ion exchange mechanisms.

Extraction of La(iii), Eu(iii) and Fe(iii) was compared in n-dodecane and in two ionic liquids (ILs) [EBPip⁺] [NTf₂⁻] and [EOPip⁺] [NTf₂⁻]. Extraction mechanisms have been investigated as a function of pH.

Recovery of Rare Earth Elements (REEs) Using Ionic Solvents

Rare earth elements (REEs) are becoming more and more significant as they play crucial roles in many advanced technologies. Therefore, the development of optimized processes for their recovery, whether from primary resources or from secondary sources, has become necessary, including recovery from mine tailings, recycling of end-of-life products and urban and industrial waste. Ionic solvents, including ionic liquids (ILs) and deep-eutectic solvents (DESs), have attracted much attention since they represent an alternative to conventional processes for metal recovery. These systems are used as reactive agents in leaching and extraction processes. The most significant studies reported in the last decade regarding the recovery of REEs are presented in this review.

Enhanced adsorption of U(VI) and 241Am(III) from wastewater using Ca/Al layered double hydroxide@carbon nanotube composites

Ca/Al layered double hydroxide decorated carbon nanotube (Ca/Al-LDH@CNTs) composites were fabricated by co-precipitation method and hydrothermal aged treatment. The prepared Ca/Al-LDH@CNTs was characterized by SEM, TEM, EDS, XRD, FT-IR, UV-vis and XPS techniques, and applied to remove U(VI) from aqueous solutions under various environmental conditions (i.e., pH, ionic strength, temperature and contact time). The results indicated that the adsorption of U(VI) on Ca/Al-LDH@CNTs was four times higher than that of U(VI) on bare CNTs. The kinetic investigations reflected the chemisorption of U(VI) on Ca/Al-LDH@CNTs through oxygen-containing functional groups. The adsorption isotherms demonstrated that the adsorption of U(VI) was well fitted by Langmuir model and the maximum adsorption capacity of U(VI) on Ca/Al-LDH@CNTs was calculated to be 382.9 mg g^-1 at 289.15 K. The thermodynamic parameters calculated from temperature-dependent isotherms suggested that U(VI) adsorption on Ca/Al-LDH@CNTs were endothermic and spontaneous process. Furthermore, Ca/Al-LDH@CNTs could remove ∼91% of ²⁴¹Am(III) at pH = 8.0, which confirmed Ca/Al-LDH@CNTs as a promising material for multiply low level radionuclides' pollution remediation.

Complexation thermodynamics of tetraalkyl diglycolamides with trivalent f-elements in ionic liquids: spectroscopic, microcalorimetric and computational studies

The thermodynamics of lanthanide complexation with DGA ligands was studied in an ionic liquid.

Structural investigations on uranium(vi) and thorium(iv) complexation with TBP and DHOA: a spectroscopic study

Spectroscopic studies were carried out to understand the complexation of U(vi) and Th(iv) with tri-butyl phosphate (TBP) and N,N-dihexyl octanamide (DHOA) in different non-aqueous solvents.

Actinide ion extraction using room temperature ionic liquids: opportunities and challenges for nuclear fuel cycle applications

Studies on the extraction of actinide ions from radioactive wastes have great relevance in nuclear fuel cycle activities, mainly in the back end processes focused on reprocessing and waste management.

Benzene-centred tripodal diglycolamides for the sequestration of trivalent actinides: metal ion extraction and luminescence spectroscopic investigations in a room temperature ionic liquid

Three benzene-centred tripodal diglycolamide (Bz-T-DGA) ligands were evaluated for actinide ion extraction/complexation in an ionic liquid medium.

Structural insights into the multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate–n-dodecane solvent extraction system

Macroscopic phase behaviors in the liquid–liquid extraction are explained by microscopic, reverse micellar fluid structures containing tetranuclear Ce(iv) clusters revealed by use of X-ray spectroscopy and scattering of the light and dense organic phases.

Comparision in the solvent extraction behavior of uranium (VI) in some trialkyl phosphates in ionic liquid

Higher homologs of trialkyl phosphates (TAlP) are proposed for reprocessing of fast reactor fuels. Solvent extraction behavior of U(VI) from nitric acid medium was studied in some TAlP present in 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C8mim][NTf2]) ionic liquid. The extractants investigated were tri-n-propylphosphate (TPP), tri-n-butylphosphate (TBP), tri-n-amylphosphate (TAP), tri-n-octylphosphate (TOP), tri-iso-amylphosphate (TIAP) and tri-iso-butylphosphate (TIBP). The extraction of uranium (VI) was investigated as a function of various parameters, such as the equilibration time, [HNO3], [TAlP], temperature and nature of ionic liquid cation. The distribution ratios of U(VI) increased with an increase in the concentration of nitric acid and decreases in the order TOP>TAP~ TIAP>TBP~TIBP>TPP. The stoichiometry of the extraction was determined by slope analysis of the extraction data. Distribution ratios of U (VI) were determined at various temperatures and the thermodynamic parameters were derived. Quantitative stripping of uranium from the loaded ionic liquid phase was achieved using dilute nitric acid.

Thallium Transfer from Hydrochloric Acid Media into Pure Ionic Liquids

Pure hydrophobic ionic liquids are known to extract metallic species from aqueous solutions. In this work we have systematically investigated thallium (Tl) extraction from aqueous hydrochloric acid (HCl) solutions into six pure fluorinated ionic liquids, namely imidazolium- and pyrrolidinium-based ionic liquids with bis(trifluoromethanesulfonyl)imide and bis(fluorosulfonyl)-imide anions. The dependence of the Tl extraction efficiency on the structure and composition of the ionic liquid ions, metal oxidation state, and initial metal and aqueous acid concentrations have been studied. Tl concentrations were on the order of picomolar (analyzed using radioactive tracers) and millimolar (analyzed using inductively coupled plasma mass spectrometry). The extraction of the cationic thallium species Tl(+) is higher for ionic liquids with more hydrophilic cations, while for the TlX(z)(3-z) anionic species (where X = Cl(-) and/or Br(-)), the extraction efficiency is greater for ionic liquids with more hydrophobic cations. The highest distribution value of Tl(III) was approximately 2000. An improved mathematical model based on ion exchange and ion pair formation mechanisms has been developed to describe the coextraction of two different anionic species, and the relative contributions of each mechanism have been determined.

Synergism as a phenomenon in solvent extraction of 4f-elements with calixarenes

The objective of the review is to provide an overview on the synergistic solvent extraction of lanthanoids: β-diketone/calixarene mixtures.