Ionic Liquid Diluent Research Articles

Radiation Stability of Cations in Ionic Liquids. 4. Task-Specific Antioxidant Cations for Nuclear Separations and Photolithography

Three families of "task-specific" antioxidant organic cations that include designated sites to facilitate deprotonation following electronic excitation and ionization have been introduced. The deprotonation from the excited state is reversible, leading to minimal damage of the cation, whereas the deprotonation from the oxidized cation yields persistent aroxyl and trityl radicals. This protection improves radiation stability of ionic compounds in 2.5 MeV electron beam radiolysis. Apart from the use of such cations as structural components of room temperature ionic liquid (IL) diluents for nuclear separations, their ionic compounds involving bases of superacids are well suited for use as chemically amplified acid generator resists in electron beam lithography and extreme ultraviolet photolithography.

Liquid–liquid extraction of neodymium(iii) by dialkylphosphate ionic liquids from acidic medium: the importance of the ionic liquid cation

The ionic liquids 1-hexyl-3-methylimidazolium bis(2-ethylhexyl)phosphate, [C6mim][DEHP], 1-hexyl-1-methylpyrrolidinium bis(2-ethylhexyl)phosphate, [C6mpyr][DEHP], and tetrabutylammonium bis(2-ethylhexyl)phosphate, [N4444][DEHP], were prepared and characterized using (1)H and (13)C NMR spectroscopy. The extraction behavior of neodymium(iii) from nitrate medium by these ionic liquids, diluted with the room temperature ionic liquids 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C6mim][NTf2], 1-hexyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [C6mpyr][NTf2], and tributylmethylammonium bis(trifluoromethylsulfonyl)imide, [N1444][NTf2], was studied. The distribution ratio of neodymium(iii) was measured as a function of various parameters, such as pH, concentration of the ionic liquid extractant, nature of diluents, concentration of ionic liquid cations and nitrate anions in the aqueous phase. The extraction behavior was compared with that obtained for a solution of the molecular extractant bis(2-ethylhexyl)phosphoric acid (DEHPA) in an ionic liquid diluent. The extraction of neodymium(iii) in the ionic liquids [C6mim][DEHP] and [C6mpyr][DEHP] showed markedly different extraction properties in comparison with that of the quaternary ammonium analogue [N4444][DEHP], especially concerning the pH dependence of the extraction process. These results show that the extraction process can be tuned by the selection of the ionic liquid cation. The extraction experiments also included the trivalent rare-earth ions lanthanum(iii), cerium(iii), praseodymium(iii), ytterbium(iii) and yttrium(iii). Studies of the stripping behavior and the reusability of the ionic liquids were carried out, which indicate that the ionic liquids can be reused with no loss in activity.

Radiation-Induced Fragmentation of Diamide Extraction Agents in Ionic Liquid Diluents

N,N,N',N'-Tetraalkyldiglycolamides are extracting agents that are used for liquid-liquid extraction of trivalent metal ions in wet processing of spent nuclear fuel. This application places such agents in contact with the decaying radionuclides, causing radiolysis of the agent in the organic diluent. Recent research seeks to replace common molecular diluents (such as n-dodecane) with hydrophobic room-temperature ionic liquids (ILs), which have superior solvation properties. In alkane diluents, rapid radiolytic deterioration of diglycolamide agents can be inhibited by addition of an aromatic cosolvent that scavenges highly reactive alkane radical cations before these oxidize the extracting agent. Do aromatic ILs exhibit a similar radioprotective effect? To answer this question, we used electron paramagnetic resonance spectroscopy to study the fragmentation pathways in radiolysis of neat diglycolamides, their model compounds, and their solutions in the ILs. Our study indicates that aromatic ILs do not protect these types of solutes from extensive radiolytic damage. Previous research indicated a similar lack of protection for crown ethers, whereas the ILs readily protected di- and trialkyl phosphates (another large class of metal-extracting agents). Our analysis of these unanticipated failures suggests that new types of organic anions are required in order to formulate ILs capable of radioprotection for these classes of solutes. This study is a cautionary tale of the fallacy of analogical thinking when applied to an entirely new and insufficiently understood class of chemical materials.

Streaming Potential Hypothesis for Ionic Polymer Transducers in Sensing: Roles of Ionomer State and Morphology

To date, consensus has not been reached on the underlying physical mechanism responsible for the experimentally observed sensing response of ionic polymer transducers, sometimes referred to as ionic polymer-metal composites. It is understood that a robust hypothesis will be able to accommodate a range of experimental observations. Moreover, because the actual morphology of ionic polymers is (a) an open topic and (b) expected to vary, a robust sensing hypothesis should additionally be decoupled from any particular morphological assumption. Explored here is the streaming potential hypothesis. As per this hypothesis, the magnitude of the predicted electromechanical response will vary with assumed morphology, but will always exist. This study demonstrates scenarios including predicting the evolution of sensing with diluent and cation variations for two morphological propositions. Specifically, sensing predictions are offered for a Nafion-based sensor (a) exchanged with lithium versus sodium cations, (b) imbued with water versus ionic liquid diluents, and (c) each of these cases is considered for a parallel circular cylindrical channel morphology versus a spherical cluster morphology. Both candidate morphologies correctly predict higher sensitivity for the lithium exchanged and water imbued cases.

Room temperature ionic liquid diluent for the mutual separation of europium(III) from americium(III)

The extraction behavior of (152+154)Eu(III) and 241Am(III) in a solution of bis(2-ethylhexyl)phosphoric acid (D2EHPA) or bis(2-ethylhexyl)diglycolamic acid (HDEHDGA) in the ionic liquid, 1-octyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide (omimNTf 2), was studied at 298 K. The extractant HDEHDGA was synthesized and characterized by IR, 1H NMR and mass spectroscopy. The effect of various parameters such as the concentrations of nitric acid, D2EHPA, HDEHDGA and diethylenetriaminepentaacetic acid (DTPA) on the extraction behavior of 241Am(III) and (152+154)Eu(III) was studied and the results are reported in this paper. Superior extraction of the target metals and excellent separation factors achieved with the use of the ionic liquid diluent indicates the feasibility of separating lanthanides from actinides present in high-level liquid waste (HLLW).

Extraction of americium(III) from nitric acid medium by CMPO-TBP extractants in ionic liquid diluent

Extraction of americium(III) from nitric acid medium by CMPO-TBP extractants in ionic liquid diluent

Extraction of americium(III) from nitric acid medium by CMPO-TBP extractants in ionic liquid diluent

Extraction of americium(III) from nitric acid medium by a solution of tri-n-butylphosphate (TBP) and n-oc-tyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in room temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (bmimNTf 2 ), was studied and the results were compared with that obtained with CMPO-TBP in n-doddecane (n-DD). The distribution ratio of 241 Am(III) in TBP-CMPO/bmimNTf 2 was measured as a function of various parameters such as concentrations of nitric acid, CMPO, bmimNO 3 , NaN0 3 and TBP and temperature. Remarkably large distribution ratios were observed for the extraction of americium(III) when bmimNTf 2 acted as diluent and the extraction was insignificant in the absence of CMPO. The stoichiometry of metal―solvate in organic phase was determined by the slope analysis of extraction data and it indicated the formation of 1: 3 (Am: CMPO) complex in organic phase. Viscosity of TBP-CMPO/bmimNTf 2 at various temperatures and enthalpy change accompanied by the extraction of americium(III) were determined and reported in this paper.

Extraction of uranium(VI) from nitric acid medium by 1.1M tri-n-butylphosphate in ionic liquid diluent

A systematic study on the extraction of U(VI) from nitric acid medium by tri-n-butylphosphate (TBP) dissolved in a non-traditional diluent namely 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) ionic liquid (IL) is reported. The results are compared with those obtained using TBP/n-dodecane (DD). The distribution ratio for the extraction of U(VI) from nitric acid by 1.1M TBP/bmimPF6 increases with increasing nitric acid concentration. The U(VI) distribution ratios are comparable in the nitric acid concentration range of 0.01M to 4M, to the ratios measured using 1.1M TBP/DD. In contrast to the extraction behavior of TBP/DD, the D values continued to increase with the increase in the concentration of nitric acid above 4.0M. The stoichiometry of uranyl solvate extracted by 1.1M TBP/IL is similar to that of TBP/DD system, wherein two molecules of TBP are associated with one molecule of uranyl nitrate in the organic phase. Ionic liquid alone also extracts uranium from nitric acid, albeit to a small extent. The exothermic enthalpy accompanying the extraction of U(VI) in TBP/bmimPF6 decreases with increasing nitric acid and with TBP concentrations.