Ali Ouadi

Understanding the Extraction Mechanism in Ionic Liquids: UO2 2+/HNO3/TBP/C4-mimTf2N as a Case Study

Abstract The extraction of U(VI) by tributylphosphate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide), C4-mimTf2N, has been studied as a function of TBP and HNO3 initial concentrations. Extraction measurements have been completed by UV-vis spectroscopy in order to get insights into the extraction mechanism. The proposed chemical model describes the data through a fit of uranyl distribution ratios, while some other suggestions are unable to do so. In this model, uranyl extraction is proposed to proceed via cation exchange at low initial acidities ([UO2(TBP)n]2+ versus C4-mim+ and H+) and via anion exchange at high HNO3 concentrations ([(UO2(NO3)3(TBP)m]− versus Tf2N−). By contrast to the usual TBP/dodecane organic phase, the IL system does not favor the neutral species UO2(NO3)2(TBP)2, and TBP does not extract nitric acid.

Determination of Successive Complexation Constants in an Ionic Liquid: Complexation of UO22+ with NO3− in C4-mimTf2N Studied by UV−Vis Spectroscopy

The complexation of UO(2)(2+) with NO(3)(-) has been investigated in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide by UV-vis spectroscopy at T = 18.5 degrees C. The complexation is evidenced through the appearance of four peaks at 425, 438, 453, and 467 nm. EXAFS data indicate that the trinitrato complex, UO(2)(NO(3))(3)(-), is dominating the speciation for a reagent ratio of [NO(3)(-)]/[UO(2)(2+)] > 3. Assuming three successive complexation steps, the conditional stability constants are calculated, the individual absorption spectra are derived, and a speciation plot is presented.

Competitive Complexation of Nitrates and Chlorides to Uranyl in a Room Temperature Ionic Liquid

By coupling EXAFS, UV-vis spectroscopy, and molecular dynamics and quantum mechanical calculations, we studied the competitive complexation of uranyl cations with nitrate and chloride ions in a water immiscible ionic liquid (IL), C(4)mimTf(2)N (C(4)mim(+): 1-butyl-3-methyl-imidazolium; Tf(2)N(-) = (CF(3)SO(2))(2)N)(-): bis(trifluoromethylsulfonyl)imide). Both nitrate and chloride are stronger ligands for uranyl than the IL Tf(2)N(-) or triflate anions and when those anions are simultaneously present, neither the limiting complex UO(2)(NO(3))(3)(-) nor UO(2)Cl(4)(2-) alone could be observed. At a U/NO(3)/Cl ratio of 1/2/2, the dominant species is likely UO(2)Cl(NO(3))(2)(-). When chloride is in excess over uranyl with different nitrate concentrations (U/NO(3)/Cl ratio of 1/2/6, 1/4/4, and 1/12/4) the solution contains a mixture of UO(2)Cl(4)(2-) and UO(2)Cl(3)(NO(3))(2-) species. Furthermore, it is shown that the experimental protocol for introducing these anions to the solution (either as uranyl counterion, as added salt, or as IL component) influences the UV-vis spectra, pointing to the formation of different kinetically equilibrated complexes in the IL.

Kinetics of metal extraction in ionic liquids: Eu3+/HNO3//TODGA/[C1C4im][Tf2N] as a case study

The kinetics of metal transfer in the system Eu3+/HNO3//TODGA/[C1C4im][Tf2N], where TODGA is N,N,N′,N′-tetraoctyl diglycolamide, is shown to depend on the chemical conditions (nitric acid and TODGA concentrations) and the time needed to reach equilibrium which may vary from less than 10 min to more than 4 h. At [HNO3] = 4 M, a detailed kinetic study is performed for two different concentrations of TODGA. It is shown that the time required for water and acid solubilisation in the IL phase is very short, as is the time for IL solubilisation in the aqueous phase. By contrast, the extraction of Eu(III) takes more than 100 min to be completed and depends on the TODGA concentration. On the basis of these experimental facts, a simple kinetic model is proposed which is able to account for the data.

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

We present new results on the liquid-liquid extraction of uranium (VI) from a nitric acid aqueous phase into a tri-n-butyl phosphate/1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (TBP/[C4 mim][Tf2 N]) phase. The individual solubilities of the ionic-liquid ions in the upper part of the biphasic system are measured over the whole acidic range and as a function of the TBP concentration. New insights into the extraction mechanism are obtained through the in situ characterization of the extracted uranyl complexes by coupling UV/Vis and extended X-ray absorption fine structure (EXAFS) spectroscopy. We propose a chemical model to explain uranium (VI) extraction that describes the data through a fit of the uranyl distribution ratio DU . In this model, at low acid concentrations uranium (VI) is extracted as the cationic complex [UO2 (TBP)2 ](2+) , by an exchange with one proton and one C4 mim(+) . At high acid concentrations, the extraction proceeds through a cationic exchange between [UO2 (NO3 )(HNO3 )(TBP)2 ](+) and one C4 mim(+) . As a consequence of this mechanism, the variation of DU as a function of TBP concentration depends on the C4 mim(+) concentration in the aqueous phase. This explains why noninteger values are often derived by analysis of DU versus [TBP] plots to determine the number of TBP molecules involved in the extraction of uranyl in an ionic-liquid phase.

Perrhenate complexation by uranyl in traditional solvents and in ionic liquids: a joint molecular dynamics/spectroscopic study.

The complexation of perrhenate (ReO(4)(-)) anions by the uranyl (UO(2)(2+)) cation has been investigated by joint molecular dynamics simulations and spectroscopic (UV-vis, TRLFS, and EXAFS) studies in aqueous solution, acetonitrile, and three ionic liquids (ILs), namely, [Bmi][Tf(2)N], [Me(3)BuN][Tf(2)N], and [Bu(3)MeN][Tf(2)N] that are based on the same Tf(2)N(-) anion (bis(trifluoromethylsulfonyl)imide) and either Bmi(+) (1-butyl,3-methylimidazolium), Me(3)BuN(+), or Bu(3)MeN(+) cations. They show that ReO(4)(-) behaves as a weak ligand in aqueous solution and as a strong ligand in acetonitrile and in the ILs. According to MD simulations in aqueous solution, the UO(2)(ReO(4))(2) complex quickly dissociates to form UO(2)(H(2)O)(5)(2+), while in acetonitrile, a stable UO(2)(ReO(4))(5)(3-) species forms from dissociated ions. In the ILs, the UO(2)(ReO(4))(n)(2-n) complexes (n = 1 to 5) remained stable along the dynamics, and to assess their relative stabilities, we computed the free energy profiles for stepwise ReO(4)(-) complexation to uranyl. In the two studied ILs, complexation is favored, leading to the UO(2)(ReO(4))(5)(3-) species in [Bmi][Tf(2)N] and to UO(2)(ReO(4))(4)(2-) in [Bu(3)MeN][Tf(2)N]. Furthermore, in both acetonitrile and [Bmi][Tf(2)N] solutions, MD and PMF simulations support the formation of dimeric uranyl complexes [UO(2)(ReO(4))(4)](2)(4-) with two bridging ReO(4)(-) ligands. The simulation results are qualitatively consistent with spectroscopic observations in the different solvents, without firmly concluding, however, on the precise composition and structure of the complexes in the solutions.

Ionic liquid-based uranium(VI) extraction with malonamide extractant: cation exchange vs. neutral extraction

We present new insights into the extraction of uranium(VI) from a nitric acid aqueous phase into 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid ([C4mim][Tf2N]) using a malonamide extractant, namely N,N′-dimethyl-N,N′-dibutylmalonamide (DMDBMA). UV-vis absorption spectrophotometry and extended X-ray absorption fine structure (EXAFS) experiments have been carried out on the extracted phases and new extraction data were used in order to model the mechanism lying behind the U(VI) extraction. We show that two different uranyl species are involved, as a function of the aqueous nitric acid concentration: the cation UO2(DMDBMA)x2+ (2 ≤ x ≤ 3) at low acid concentration, and the neutral UO2(NO3)2(DMDBMA) at high acid concentration. The former is extracted by exchange with 2 protons, while the latter is co-extracted with a HNO3 molecule. We show that the uranium extraction is performed without the direct help of IL ions, although the latter pollute noticeably the aqueous phase.

Synthesis of New Calixarene-Phosphine Oxides and Their Extraction Properties in Ionic Liquids

Abstract New calix[4]arenes functionalized by Alk2P(O)CH2 and N-methylimidazolium groups at the opposite rims of the macrocyclic skeleton have been synthesized and characterized. Their extraction properties towards of Eu3+ and Am3+ in ionic liquid were investigated.

Automated and efficient radiosynthesis of [18F]FLT using a low amount of precursor

INTRODUCTION Since 1991 until now, many radiosyntheses of [(18)F]FLT have been published. Most of them suffer from side reactions and/or difficult purification related to the large amount of precursor necessary for the labeling step. A fully automated synthesis using only commercial and unmodified materials with a reduced amount of precursor would be desirable. METHODS We first explored the possibility to elute efficiently [(18)F]fluorine from commercial and unmodified cartridges with various amount of base. Based on these results, 10mg and 5mg of precursors were used for the fluorination step. The best conditions were transposed in an automated process for a one pot two steps synthesis of labeled FLT. RESULTS Using commercial and non-treated carbonate form of QMA cartridges, we were able to elute quantitatively the [(18)F]fluorine with a very low amount of base (0.59mg) and, with only 5mg of precursor, to perform an efficient fluorination reaction with up to 94% incorporation of [(18)F]fluorine. The synthesis was fully automated and radiochemical yields of 54% (decay corrected) were obtained within a synthesis time of 52minutes. CONCLUSION We demonstrate that a fully automated and efficient radiosynthesis of [(18)F]FLT is feasible with only 5mg of precursor. Compare to the present state of the art, our method provides high yields of pure [(18)F]FLT and is broadly adaptable to other synthesis automates.

Imaging thrombosis with 99m Tc-labeled RAM.1-antibody in vivo

INTRODUCTION Platelets play a major role in thrombo-embolic diseases, notably by forming a thrombus that can ultimately occlude a vessel. This may provoke ischemic pathologies such as myocardial infarction, stroke or peripheral artery diseases, which represent the major causes of death worldwide. The aim of this study was to evaluate the specificity of radiolabeled Rat-Anti-Mouse antibody (RAM.1). METHODS We describe a method to detect platelets by using a RAM.1 coupled with the chelating agent hydrazinonicotinic acid (HYNIC) conjugated to 99mTc, for Single Photon Emission Computed Tomography (SPECT). To induce platelet accumulation at a site of interest, we used a mouse model of FeCl3 induced injury of the carotid artery. 90 min after i.v. injection of [99mTc][Tc(HYNIC)-RAM.1], biodistribution of the radiolabeled RAM.1 was assessed, SPECT imaging and histological analysis were performed on the mice that underwent FeCl3-induced vessel damage. RESULTS We demonstrated a quick and strong affinity of the radiolabeled RAM.1 for the platelet thrombus. Results clearly demonstrated the ability of this radioimmunoconjugate for detecting thrombi from 10 min post injection with an exceptional thrombi uptake. Using FeCl3, the median ratio between the thrombus and the background was 12.4 (range 9.3-42.3) as compared to 1.0 (range: 0.86-2.7) p < 0.05 when using 0.9% NaCl. CONCLUSION Thanks to the high sensitivity of SPECT, we provided evidence that [99mTc][Tc(HYNIC)-RAM.1] represents a powerful tool to detect localized platelet thrombi which could potentially be used in humans. Because of the relative low cost and high sensitivity, these results encourage further study like the detection of non-induced thrombus and further developments toward clinical application. This is further supported by the fact that RAM.1 recognizes human platelets.