Molecular Diluents Research Articles

Effect of branching in the alkyl chain of diglycolamide on the sequestration of tetravalent actinides: solvent extraction and theoretical studies.

DGA (diglycolamide) ligands show a different extraction behavior of trivalent metal ions by changing the branching alkyl chain length as well as the branching at the methylene position. There are no studies of these factors on the extraction efficiency of these DGA derivatives for the extraction of tetravalent actinides. We have evaluated four different DGA derivatives for the extraction of Np, Pu, and Th from molecular diluents. The n-butyl derivative shows enhanced extraction efficiency and branching gives rise to a reduction in the extraction efficiency of tetravalent ions. The distribution ratios are higher in pure octanol than in a mixture of 30% octanol and 70% n-dodecane. This behavior is in marked difference to that of the extraction of trivalent ions where the addition of an alcohol generally decreases the distribution ratio of trivalent ions due to the ligand-modifier intercation, poor aggregation or micelle formation tendency of DGAs in polar solvents. This suggests that micelle-mediated extraction may not be the dominating factor for the extraction of tetravalent metal ions. Slope analysis suggests the involvement of only two DGA molecules in the extracted species suggesting no/poor possibility of micelle formation in the present system. The higher extraction in pure octanol may be due to a better solubility of the extracted complexes in this polar medium compared to the mixture of octanol and n-dodecane. The water and acid uptake, the back extraction, and the radiation stability of the solvent systems were also investigated. DFT studies were performed to get a better insight into the extraction and complexation of the different DGA solvent systems.

Extractive Mass Transfer of Zr(IV) into a Hydrophobic Ionic Liquid Medium Containing Diglycolamide Extractant: Solvent Extraction and Spectroscopic Analysis.

Solvent extraction of Zr(IV) in ionic liquid (IL) medium is less known and Zr(IV) - IL chemistry indeed needs exploration to realize the coordination approach of Zr(IV) in IL phase. In view of this, in the present work, a strongly hydrophobic imidazolium based IL: 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([C8mim][NTf2]) as the medium containing a diglycolamide (DGA) extractant: N,N,N',N'-tetra-n-octyldiglycolamide (TODGA) was opted to understand the extraction behavior of Zr(IV) from nitric acid medium. Different experimental parameters such as the concentration of initial nitric acid, initial feed metal concentration, equilibration time and ligand concentration were tuned to unravel the extraction efficiency of the proposed IL phase towards Zr(IV). The extraction scenario was completely dependent on the hydrophobicity of IL diluent and increasing extraction trend with an increase in feed acidity along with the coordination of two TODGA molecules ensured Zr(IV) - complex formation in a neutral solvation mechanistic pathway. The extraction trend of Zr(IV) was compared with molecular diluent (n-dodecane (n-DD)) containing TODGA and a phase modifier: N,N-dihexyloctanamide (DHOA). The coordination aspect of Zr(IV) with ligand in IL phase was ascertained spectroscopically to validate Zr(IV) loading in IL phase. Thermodynamics of Zr(IV) extraction revealed the nature of the extraction process and the complex formation.

Aliquat 336 in Solvent Extraction Chemistry of Metallic ReO4- Anions.

A study of the liquid-liquid extraction of ReO4- anions from hydrochloric acid solutions using the ionic liquid Aliquat 336 (QCl: trialkyl(C8-C10)methylammonium chloride) via the well-known method of slope analysis along with the determination of the process parameters is presented. This study employs CCl4, CHCl3 and C6H12 as diluents. This study was carried out at room temperature (22 ± 2) °C and an aqueous/organic volumetric ratio of unity. The ligand effect on the complexation properties of ReO4- is quantitatively assessed in different organic media. The organic extract in chloroform media is examined through 1H, 13C and 15N NMR analysis as well as the HRMS technique and UV-Vis spectroscopy in order to view the anion exchange and ligand coordination in the organic phase solution. Final conclusions are given highlighting the role of the molecular diluent in complexation processes and selectivity involving ionic liquid ligands and various metal s-, p-, d- and f-cations. ReO4- ions have shown one of the best solvent extraction behaviors compared to other ions. For instance, the Aliquat 336 derivative bearing Cl- functions shows strongly enhanced extraction as well as pronounced separation abilities towards ReO4-.

Mutual Solubilities between Ethylene Glycol and Organic Diluents: Gas Chromatography and NMR.

In this work, the mutual solubilities of sets of organic diluents (CHCl3, C6H6, C2H4Cl2, CCl4, C6H12, and n-hexane) with the organic compound ethylene glycol are investigated via gas chromatography (GC). The experimental data measured for these binary organic systems are used to adjust the future nonaqueous systems for the solvent extraction of various metals with ligands. The obtained results showed that the solubility of ethylene glycol decreased in the order CHCl3 > C6H6 > C2H4Cl2 > CCl4(0%) ≈ C6H12 ≈ n-hexane. On the other hand, the solubility of the tested traditional organic diluents in ethylene glycol decreased in the following order: C6H6 > CHCl3 > C2H4Cl2 > n-hexane > C6H12 > CCl4. 1H NMR was also used as an analytic method in order to compare the obtained results for the samples showing significant solubility only, including an additional study with 1,2- or 1,3-propanediol. The enhanced solubility of the C6H6 compound in ethylene glycol was identified here as critical due to the GC technique, which will be without future consequences in chemical technology. Therefore, it was found that the best molecular diluent for the recovery of metals among the tested ones is C6H12, with a green protocol as the new paradigm, replacing the aqueous phase with another nonaqueous phase, i.e., a second organic diluent.

Extraction of Np(IV/VI) from nitric acid medium using three different tripodal diglycolamide ligands in ionic liquid: Batch extraction, spectroscopic and electrochemical investigations

Complexation of Np(IV) and Np(VI) ions was studied in a room temperature ionic liquid (C4mim.NTf2) using three tripodal ligands with an ‘N’ atom, a ‘C’ atom and a benzene ring at the center, which are termed as LI, LII and LIII, respectively . The studies include solvent extraction, visible-near infrared (vis-NIR) spectroscopy, and cyclic voltammetry. The trend of the extraction of Np4+ was LIII > LII > LI, which resembled that reported before in a mixture of molecular diluents but with about 10 times higher ligand concentration. Np(VI) was extracted to a much lower extent than Np(IV). Slope analysis of Np(IV) extraction suggested formation of Np(NO3)4.L species for LII and LIII, while a cationic species of the type [Np(NO3)2.L]2+ was seen for LI. On the other hand, for Np(VI), formation of NpO2(NO3)2.L species was proposed for LI and LIII and [NpO2(NO3).L]+ for LII. All the extracted species conform to a ‘solvation’ type extraction except for Np(IV) with LI and Np(VI) with LII which point to a ‘cation-exchange’ mechanism. The complexation of the metal ions with the tripodal ligands was supported by peak shifts in the vis-NIR as well as the cyclic voltammetric studies.

Sequestration of Np4+ and NpO22+ ions by using diglycolamide-functionalized azacrown ethers in C8mim·NTf2 ionic liquid: Extraction, spectroscopic, electrochemical and DFT studies

Complexation of Np4+ and NpO22+ ions was studied in a room temperature ionic liquid (C8mim•NTf2) using two multiple diglycolamide (DGA) ligands with three and four DGA arms tethered to the nitrogen atoms of the aza-9-crown-3 and -12-crown-4 scaffolds termed as LI and LII, respectively. The studies include solvent extraction, UV–visible spectrophotometry, cyclic voltammetry, and density functional theory (DFT). While the extraction of NpO22+ ion, as a function of the nitric acid concentration, resembled that of the ‘solvation’ mechanism, seen in case of neutral donor ligands in molecular diluent, an opposite trend was observed for the Np4+ ion suggesting a ‘cation-exchange’ mechanism often operating in the case of ionic liquid-based solvent systems. Slope analysis suggested formation of Np(NO3)]3+•L and NpO2(NO3)2•L extracted species for the extraction of Np4+ and NpO22+, respectively, in both the ligand systems. The complexation of the metal ions was supported by peak shifts in the UV–visible spectrophotometric as well as cyclic voltammetric studies. DFT studies were carried out to get structural information of the complexes.

Synthesis of fatty acid-based ammonium ionic liquids and their application for extraction of Co(II) and Ni(II) metals ions from aqueous solution

Leaching of cobalt and nickel into diverse water streams has become an environmental hazard and is continuously impacting human health through the food chain. Solvent extraction is the most widely accepted for separating these metals, but traditional extractants employed in conjunction with molecular diluents often lack selectivity and caused major environmental hurdles. Therefore, the development of cost-effective, environmentally friendly technologies for recovering these heavy metals has been strongly encouraged in recent years. Herein, two halogens free, low viscous, biocompatible fatty acid-based hydrophobic ionic liquids (ILs), i.e., methytrioctylammonium oleate, methytrioctylammonium linoleate were synthesized, analytically characterized and employed for recovery of cobalt, Co(II) and nickel, Ni(II) from their aqueous solutions. Extraction behaviour of Co(II) and Ni(II) was further evaluated by varying equilibrium time, ILs molar concentration, metal loading, and temperature. Thermodynamic parameters such as enthalpy change and Gibbs free energy change were also studied during extraction process. Slope analysis suggested that the extraction mechanism was an exothermic process that followed ion-transfer from the aqueous phase to the organic phase. Results showed that both fatty acid based–ILs were found to be capable of extracting >99% of Co(II) and Ni(II) from aqueous solutions at 298 K, in 15 min of shaking time using a 1:1 (org: aq.) ratio at low concentrations of 2.5–10 g L−1. Furthermore, for methyltrioctylammonium oleate IL, Co(II) extraction was selectively preferred over Ni(II) extraction when the metal concentration was increased to above to 10 g L−1. The stripping results showed that 2 M H2SO4, and 2 M HCl successfully stripped out >99% of Co(II) and Ni(II) from the organic phase, respectively compared to HNO3.

Separation of Americium from a Complex Matrix by Solvent Extraction Using CyMe4BTPhen in a Room Temperature Ionic Liquid Diluent

ABSTRACT The extraction performance and mechanism of 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-1,10-phenanthroline (CyMe4BTPhen) in the room temperature ionic liquid 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][NTf2]) have been studied and are herein reported. Americium is extracted from nitric acid solutions by cation exchange and is most efficient at low (< 1 M) nitric acid concentrations as opposed to the high (4 M) concentration preferred when using most traditional molecular diluents. The kinetics are slow, taking 24 hours to achieve quantitative extraction of americium but are greatly improved, achieving the same within 8 hours, by dilution with 1-octanol. High SFAm/Eu > 3000 were achieved although decontamination factors for americium from more complex matrices were non-competitive with extraction using traditional molecular diluents. Modest improvements in decontamination factor were attained by the addition of the hydrophilic reagent N,N,N’,N’-tetraethyl diglycolamide (TEDGA).

Pyridine diglycolamide: A novel ligand for plutonium extraction from nitric acid medium

A novel ligand N, N, N’, N’ tetra-isobutyl pyridine diglycolamide (PDGA) was synthesized and tested for extraction of actinides and fission products present in high level liquid waste (HLLW). The ligand was studied in presence of two different diluents- nitrobenzene (NB), a molecular diluent and 3-methyl-1-octyl immidazolium bis[(trifluoromethyl)sulfonyl] imide, an Ionic Liquid (IL). Unusual selectivity towards tetravalent plutonium over minor actinides and alkali & alkaline metal ions present in nuclear waste was showed by PDGA in presence of NB as diluent. The trend in kinetics of extraction as well as dependency of DPu(IV) values with nitric acid concentration was found to be different for two diluents studied. Mechanism of extraction was also varied for the two diluents studied. It followed solvation mechanism for NB whereas for IL it was a combination of solvation and ion-exchange mechanism. The calculated Gibbs free energy of extraction, ΔGext for Pu(IV) using density functional theory was found to be higher than that of other competitive metal ions corroborating the results from solvent extraction experiment. Further, ΔGext was found to be highly negative for metal and ionic liquid cations thus complimenting the experimental findings of ion exchange mechanism for a metal cation with cation of the ionic liquid.

Novel Bis(diphenylcarbamoylmethylphosphine oxide) Ligand for Effective Extraction of Actinides and Lanthanides from Nitric Acid Solutions

ABSTRACT A novel polydentate neutral organophosphorus ligand N,N’-dicyclohexyl-N,N’-bis(diphenylphosphinoylacetyl)urea 1 containing two Ph2P(O)CH2C(O)N(cyclo-Hex)- bidentate moieties connected by a carbonyl group through amide nitrogen atoms was studied as an extractant for U(VI), Th(IV) and lanthanides(III) ions from HNO3 solutions into molecular diluents and ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The influence of composition of aqueous and organic phases on the extraction efficiency was elucidated and stoichiometry of the complexes extracted was determined. Slope analysis indicates that the ligand 1: metal ratio in the extracted complexes in ionic liquid is less than that in 1,2-dichloroethane. The extraction efficiency of bis-CMPO 1 towards U(VI), Th(IV) and lanthanides(III) increased significantly in the presence of ionic liquid. Bis-CMPO ligand 1 in ionic liquid was found to possess a higher extraction efficiency towards U(VI), Th(IV) and lanthanides(III) ions than its mono analog diphenyl-(N,N-dibutylcarbamoylmethyl)-phosphine oxide 2. The role of Tf2N− anions in increasing the efficiency of Ln(III) extraction in the presence of an ionic liquid is discussed.

Understanding the extraction behaviour of UO22+ and Th4+ using novel picolinamide/N-oxo picolinamide in ionic liquid: A comparative evaluation with molecular diluent

The manuscript deals with efficient separation of hexavalent UO22+ and tetravalent Th4+ from aqueous acidic waste solution in ‘green way’ using ionic liquid with novel picolinamide (L I) and N-oxo picolinamide (L II) based ligands. A comparative evaluation was carried out to understand the extraction mechanism, kinetics, thermodynamics, speciation, radiolytic stability and stripping behaviour of UO22+ and Th4+ in ionic liquid vis-a-vis molecular diluent. The investigation demonstrates the predominance of ‘cation exchange’ mechanism in ionic liquid and ‘solvation' mechanism in n-dodecane based systems. The slower extraction kinetics in ionic liquid was attributed to the ‘viscosity effect’. The extractive mass transfer processes were found to be spontaneous, endothermic and entropically driven in nature. The picolinamide and N-oxo picolinamide ligands were found to form inner-sphere complexes in ionic liquid as well as n-dodecane. In molecular diluent, the species involved for separation of UO22+ were UO2(NO3)2. 2 LI and UO2(NO3)2. L II, respectively, whereas in ionic liquid thet were [UO2(NO3). 2 L]+ and [UO2(NO3). L]+. For Th4+, in molecular diluent, the most plaussible extracted species were Th(NO3)4. 2 L I and Th(NO3)4. L II, while in ionic liquid they were [Th(NO3)2. 2 L]2+ and [Th(NO3)2. L]2+, respectively. Ionic liquid based solvent systems exhibited more radiolytic stability compared to that in molecular diluent. The CO32− was more effective aqueous phase complexing agent to back extract UO22+, while C2O42− exhibited the same for Th4+.

Solvent Extraction of Lanthanides(III) from Nitric Acid Solutions with Novel Functionalized Ionic Liquids Based on the Carbamoyl(methyl)phosphine Oxide Pattern in Molecular Diluents

ABSTRACT The extraction of lanthanides(III) from nitric acid solutions in the systems involving novel functionalized ionic liquids based on cationic carbamoyl(methyl)phosphine oxide (CMPO) derivatives and dinonylnaphthalenesulfonate anions in molecular diluents was studied. The stoichiometry of the Ln(III) extracted species was determined using slope analysis. The influence of the concentration of HNO3 in the aqueous phase and the nature of organic diluents on the metal ion extraction efficiency into the organic phase was considered. Functionalized ionic liquids 1-[3-[[(diphenylphosphinyl)acetyl]amino]propyl]-1H-imidazol-1-ium dinonylnaphthalenesulfonate (L1HA) and 1-[2-[[(diphenylphosphinyl)acetyl]amino]ethyl]-pyridin-2-ium dinonylnaphthalenesulfonate (L2HA) demonstrate higher extraction ability towards Ln(III) than their neutral CMPO analog, diphenylphosphorylacetic acid N-nonylamide (L).

Comparative uptake studies on trivalent f-cations from acidic feeds using two extraction chromatography resins containing a diglycolamide in molecular diluent and ionic liquid

Low molecular weight diglycolamide (DGA) extractants were tested for the extraction of europium(III) and americium(III) from nitric acid solutions in n-dodecane, a molecular diluent and 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide (C4mim⋅NTf2), a room temperature ionic liquid, as the diluents. N,N,N’,N’-tetra-n-butyl diglycolamide (TBDGA) was selected for extraction chromatography (XC) studies involving Eu(III) and Am(III). While the TBDGA resin containing n-dodecane gave reasonably high Kd values, that containing the ionic liquid showed higher Eu(III) uptake values. Compared to Eu(III), Am(III) was extracted by the resins to a lower extent. The loaded Eu(III) was back extracted from the resin using 0.05 M EDTA solutions in a buffered medium containing 1 M guanidine carbonate. Reusability studies indicated that, while the ionic liquid-based resin can be conveniently recycled five times with very marginal decrease in the percentage extraction values, there was a sharp decrease in the percent extraction after three cycles with the n-dodecane-based resin. The uptake data was fitted into different isotherm models and the results conformed to the Langmuir model. Based on the batch uptake studies, columns were prepared and the breakthrough as well as elution profiles were obtained. The elution profiles were found to be sharp without any significant tailing.

Ionic liquid (IL) cation and anion structural effects on the extraction of metal ions into N-alkylpyridinium-based ILs by a macrocyclic polyether

ABSTRACT Previous studies of the effect of IL cation/anion hydrophobicity and the nature of the aqueous phase anion on the partitioning of alkali and alkaline earth cations between an acidic aqueous phase and 1,3-dialkylimidazolium-based or quaternary ammonium-based ILs in the presence of a crown ether have revealed significant similarities between the behavior of the two IL families. To further explore the generality of these observations and their potential application in the rational design of ILs for use as replacements for the molecular diluents typically employed as extraction solvents, the extraction of several metal ions (Na+, Sr2+ and Ba2+) from nitric and hydrochloric acid solutions by dicyclohexano-18-crown-6 (DCH18C6) into a series of N-alkylpyridinium-based ILs (Cn-pyr+ ILs) has been studied. Although much of the extraction behavior observed in these systems is consistent with that seen for the 1,3-dialkylimidazolium and quaternary ammonium-based ILs, certain observations, in particular the effect of IL cation hydrophobicity on divalent metal ion extraction from HNO3 by N-alkylpyridinium-ILs bearing long (dodecyl- and tetradecyl-) alkyl chains, cannot be fully explained by the established three-path model for metal ion partitioning. Instead a complete description of metal ion extraction in these systems requires consideration of the aggregation of the IL cation in the aqueous phase. The effects of this aggregation on the efficiency and selectivity of metal ion extraction into Cn-pyr+ ILs by the crown ether are systematically explored.

Comparative study on aqueous acid free UO2 dissolution-extraction using DHOA adduct into room temperature ionic liquid/supercritical carbon dioxide/n-hexane

Abstract Feasibility was established for direct dissolution-extraction of uranium employing adduct of N,N-dihexyl octanamide (DHOA), thus eliminating discrete aqueous phase and free acid usage. Various aspects of dissolution of solid uranium dioxide and extraction of uranium into molecular diluent viz. n-hexane and neoteric solvents viz. room temperature ionic liquid (RTIL) and supercritical carbon dioxide (SC CO2) were studied. The organic adduct was found to have composition DHOA.(HNO3)0.78(H2O)0.4. Adduct miscibility and UO2 dissolution behavior was markedly different for RTIL and n-hexane. The dissolution process, studied by monitoring UV–Vis spectra, was found to be pseudo first order with a rate constant of of 0.074 min−1 and 0.036 min−1 for n-hexane and RTIL respectively. Irrespective of medium, dissolution-extraction efficiency of ≥90% was achievable. Using RTIL for dissolution-extraction medium and SC CO2 for stripping is promising in terms of overall efficiency as well as RTIL recovery by avoiding aqueous cross contamination.

Effect of diluent on the extraction of europium(iii) and americium(iii) with N,N,N',N'-tetraoctyl diglycolamide (TODGA).

Solvent extraction of Eu3+ and Am3+via N,N,N′,N'-tetraoctyl diglycolamide (TODGA) dissolved in different molecular diluents was studied. The diluent types used in this work were primary and secondary alcohols, secondary ketones and alkanes. Effects of concentration of extracting agent, temperature, diluent type and its carbon chain length on the extractions were determined. Distribution ratios of Eu3+ and Am3+ showed high dependence on the diluent type as well as the carbon chain length within the same type of diluent. The highest distribution ratios for both Eu3+ and Am3+ as well as the separation factors of Eu3+ over Am3+ were observed in the alkane diluents. Unexpectedly high distribution ratios for Eu3+ and Am3+ were observed in polar diluents with 5 carbon atoms in the chain, clearly standing out against the general trends. It was found that Eu3+ and Am3+ extraction via TODGA is enthalpy driven in all the studied diluents and that extraction is more exothermic in alkane diluents. Analysis of the stoichiometry of the extracted complexes shows that the average ligand number of TODGA molecules in the extracted complex is lower for Am3+ compared to Eu3+ except for with alkane diluents.

Effect of alkyl chain length on the extraction properties of U and Th using novel CnmimNTf2/isophthalamide systems

An attempt was made to investigate the structural modification of CnmimNTf2 ionic liquid in combination with a novel ligand, 5-bromo-N1,N3-bis(1-methyl-1H-pyrazol-3-yl)isophthalamide on the extraction properties of tetra and hexavalent actinides. In C4mimNTf2, C6mimNTf2, the extraction processes predominantly followed the ‘cation exchange’ mechanism involving the species: [UO2(NO3)L]+ and [Th(NO3)2L]2+, whereas, in C8mimNTf2, the ‘solvation’ mechanism was found to be predominant involving neutral species UO2(NO3)2L2 and Th(NO3)4L3. The speciation was further confirmed by investigating the participation of imidazolium cation in extraction. In ionic liquid, the extraction processes were slower compared to that in the molecular diluent. The time required to attain the equilibrium D values followed the trend: C4mimNTf2 < C6mimNTf2 < C8mimNTf2. This was attributed to the viscosity induced slow mass transfer. At 1 M HNO3, the D values for uranyl and thorium follow the trend C4mimNTf2 > C6mimNTf2 > C8mimNTf2, which was ascribed to the enhancement in organophilicity of the cation on increasing the length of the side chain and hence the effect on their dissolution in water. Three cycles of 1 mM aqueous sodium carbonate solution and four cycles of 1 mM oxalic acid solution were sufficient for almost quantitative back extraction of U and Th, respectively.C8mimNTf2 based systems were better radio-resistant compared to the lower homologue.

Exploring novel functionality for efficient extraction of UO22+ and Th4+in ionic liquid: Mechanism, speciation, selectivity, stability and stripping

Novel ligand functionality, 5-bromo-N1, N3-bis(4,6-dimethylpyridin-2-yl)isophthalamide, was explored for highly efficient and selective separation of UO22+ and Th4+ in pyridinium based ionic liquid. The comprehensive investigation revealed that, both in ionic liquid as well as in molecular diluents the extraction predominantly proceeded via ‘solvation’ mechanism. However, the species involved in extraction were UO2(NO3)2, L and Th(NO3)4, L in ionic liquid, while UO2(NO3)2, 2 L and Th(NO3)4, 3 L in molecular diluent. The highly viscous ionic liquid resulted the mass transfer slower during extraction. In ionic liquid based system, the extraction processes were endothermic, spontaneous and entropy driven. Ionic liquid based solvent systems exhibited high radiation stability, which was attributed to the formation of resonance-stabilized aromatic cation as well as the restricted movement of radicals in viscous ionic liquid. The aqueous solution of sodium carbonate was found to be effective for the stripping of UO22+, while oxalic acid solution was found to be effective for Th4+. The solvent systems were used for processing of simulated high level waste solutions of a Research Reactor (RR) and Fast Breeder Reactor (FBR) origin.

Solvent extraction of lithium ions using benzoyltrifluoroacetone in new solvents

This work studies the solvent extraction of lithium ions from alkaline aqueous solutions by chelating agent 3-benzoyl-1,1,1-trifluoroacetone (HBTA). To develop a more eco-friendly extraction system for lithium than currently used, various hydrophobic room-temperature ionic liquids were investigated as diluents. The influence of several experimental parameters on lithium extraction was examined, including aqueous phase pH, the nature of lithium counter-ion, extractant concentration, the addition of electrically neutral co-extractant.It was found that contrary to the traditional extraction systems with molecular diluents, HBTA alone dissolved in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid extracts efficiently lithium ions from the aqueous solution. The addition of co-extractant, tri(n-octyl)phosphine oxide (TOPO) to HBTA did not result in a synergetic effect. To confirm the mechanism of lithium extraction by HBTA dissolved in ionic liquid (IL), the measurements of IL constituent ions and deprotonated HBTA concentrations in the equilibrium aqueous phase were carried out. Analysis of the results suggests that an electrically neutral lithium-HBTA extractant complex is extracted into the IL phase.The system combining HBTA extractant and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid has high selectivity for lithium over sodium but poor selectivity over calcium. We have shown also that a high stripping ratio can be obtained using relatively concentrated aqueous solutions of hydrochloric acid. Finally, it was found that the use of some deep eutectic solvents as diluents is much less efficient compared with ILs.

Radiolytic stability of pillar[5]arene-based diglycolamides

Abstract Radiolytic stability of pillar[5]arene-based diglycolamides (P5DGAs) against gamma irradiation up to 1000 kGy adsorbed dose was studied. The results reveal the increase of radiation damage degree on P5DGAs with dose. The radiolysis products of P5DGAs including the gaseous and solid products were fully characterized by 1H NMR, HR-ESI-MS, GC, and HPLC techniques. It was found that the main radiolytic gas products of P5DGAs under argon are H2, N2, CO and gaseous hydrocarbons. The solid degradation products contain phenolic hydroxyl groups and secondary amine groups. In addition, solvent extraction toward Eu(III) was performed with P5DGAs, in which about 50% decrease on extraction efficiency was observed for irradiated P5DGAs with dose of 1000 kGy in comparison with the non-irradiated one. A radiolytic degradation pathway was also proposed based on the above results. This is the first time to investigate the radiolytic stability of neat P5DGAs and P5DGAs in molecular diluent in detail and provides useful information for further application of P5DGAs in practical applications for spent fuel reprocessing.