Search

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. [ABSTRACT FROM AUTHOR]

Mutual separation of trans-plutonium actinides (Ans) from lanthanides (Lns) or adjacent Ans is challenging as they exhibit great chemical similarity. Selective Am oxidation-based Am–Lns or Am–Cm separation strategies give very high separation factors. There exist several reports on different aspects of Am3+ oxidation by NaBiO3·xH2O (x = 2–3), which suggests that the oxidation mechanism is still not well understood. We, therefore, carefully performed several experiments taking advantage of the difference in the redox chemistry of Eu3+ and Am3+. The ion exchange of Eu3+ with the interlayer Na+ in NaBiO3 was confirmed by an ionic strength variation experiment. The shift in the 001 peak of NaBiO3 in XRD and the appearance of peaks corresponding to the trivalent Ln ions in XRF after Ln3+ loading give direct evidence for Na+ exchange with Ln3+. The stability of the higher oxidation state of Am was monitored spectrophotometrically. The experimental investigations also suggested the role of Am3+ → AmO22+ transformation in NaBiO3·xH2O (x = 2–3) dissolution even at pH ∼ 1, which otherwise is difficult to achieve even with >1 M HNO3. The role of colloidal NaBiO3 particles and dissolved BiO3− in controlling or stabilizing different oxidation states of Am was also discussed. [ABSTRACT FROM AUTHOR]

AgBiO3 is reported for the exclusive oxidation of Am3+ → AmO2+ at near-neutral pH conditions. Literature methods of AmO2+ generation are generally two-step processes; i.e., Am3+ → AmO22+ oxidation followed by AmO22+ → AmO2+ reduction. These methods for Am3+ → AmO2+ oxidation use high temperatures (80–100 °C) and/or several reagents, causing the in situ presence of the AmO2+-complex rather than the AmO2+aq ions. This not only interferes with the much-needed Am–Cm selectivity but also limits the use of AmO2+aq in any other experimental study. The single-step Am3+ → AmO2+ oxidation in the present work using AgBiO3 is done at 25 °C in a non-complexing medium at pH ∼4, making it a first-of-its-kind report. Am–Eu and Am–Cm separation in a single contact, with a separation factor >104, was achieved using the present method, which is unprecedented among aqueous feed solutions. The AmO2+ generated using the present method under non-complexing pH conditions makes it also suitable for exploring the fundamental chemistry of the higher valent americyl ion. A complexation study using the thus-generated AmO2+ ion with acetate ion supports the concept. [ABSTRACT FROM AUTHOR]

AgBiO3 is reported for the exclusive oxidation of Am3+ → AmO2+ at near-neutral pH conditions. Literature methods of AmO2+ generation are generally two-step processes; i.e., Am3+ → AmO22+ oxidation followed by AmO22+ → AmO2+ reduction. These methods for Am3+ → AmO2+ oxidation use high temperatures (80–100 °C) and/or several reagents, causing the in situ presence of the AmO2+-complex rather than the AmO2+aq ions. This not only interferes with the much-needed Am–Cm selectivity but also limits the use of AmO2+aq in any other experimental study. The single-step Am3+ → AmO2+ oxidation in the present work using AgBiO3 is done at 25 °C in a non-complexing medium at pH ∼4, making it a first-of-its-kind report. Am–Eu and Am–Cm separation in a single contact, with a separation factor >104, was achieved using the present method, which is unprecedented among aqueous feed solutions. The AmO2+ generated using the present method under non-complexing pH conditions makes it also suitable for exploring the fundamental chemistry of the higher valent americyl ion. A complexation study using the thus-generated AmO2+ ion with acetate ion supports the concept. [ABSTRACT FROM AUTHOR]

Two benzene-centered tripodal diglycolamide ligands (LI and LII) were used for the extraction of Am3+ and Eu3+ from nitric acid solutions into a diluent medium of n-dodecane modified with various amounts of isodecanol. The ligands showed preferential extraction of Eu3+ over Am3+ in most cases. While the extraction of the Am3+ ion was not much affected (with a slight increase) over the entire range of diluent compositions in the case of LI, a gradual decline in the extraction of the Eu3+ ion suggested a reversal in the separation trend with Am3+ being preferentially extracted with a solution of LI in pure isodecanol. On the other hand, a sharp decline was seen for the extraction of both Am3+ and Eu3+ in the entire range of diluents containing various fractions of isodecanol when LII was used. The unusual extraction was attributed to the difference in the complexation behaviour of LI and LII, which was explained on the basis of photoluminescence (PL) spectroscopy as well as XAS studies. The PL studies suggested absence of any inner-sphere water molecules from the lifetime data, while the splitting of emisison peaks and asymmetry ratio values gave an idea about the complex geometry. On the other hand, the XAS studies gave information about the bonding in the coordination complexes. [ABSTRACT FROM AUTHOR]

Solvent extraction studies were performed to understand the extraction behavior of Np4+ and NpO22+ from acidic feeds with CMPO (octyl (phenyl)-N,N-diisobutyl carbamoyl methyl phosphine oxide) dissolved in 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide, a water immiscible ionic liquid. Slope analyses on the distribution data revealed the extraction of ML2 type species, where M = Np4+ or NpO22+, and L = CMPO. Studies were also carried out with Pu4+ and UO22+ under identical conditions. The nature of the extracted species was found to vary with the nature of the ionic species. [ABSTRACT FROM AUTHOR]

This paper reports the solvent extraction of Am3+ and Eu3+ using N,N,N′,N′,N′′,N′′-hexa-n-octylnitrilotriacetamide (HONTA) as the extractant in n-dodecane. The results are in variance with those reported previously with respect to the nature of the extracted species. The solvent extraction data were entirely different from those reported previously as the extracted species conformed to 1 : 2 (M : L) species for both Am3+ and Eu3+ ions. The structure of the extracted complex was determined by EXAFS demonstrating the three amidic ‘O’ atoms of the HONTA complex with the Eu3+ ion. In the case of the Am3+ ion, the pivotal ‘N’ atom is suggested to bond to the metal ion, which may explain the significantly more favourable extraction of Am3+vis-à-vis Eu3+. The absence of H2O molecules in the inner coordination sphere of the Eu3+–HONTA extract was confirmed by luminescence spectroscopic measurements. Complexation studies in MeOH and EtOH indicated the formation of both 1 : 1 and 1 : 2 complexes with Nd3+ ions. The results are explained on the basis of DFT calculations using HMNTA, the corresponding hexamethyl analogue of HONTA. [ABSTRACT FROM AUTHOR]

An N-pivot diglycolamide extractant (DGA-TREN) was synthesized for the first time and its complexation behaviour was studied towards trivalent lanthanide/actinide ions. The solvent extraction studies suggested a unique selectivity reversal in the extraction of trivalent actinides versus trivalent lanthanides which was observed performing extraction studies in an ionic liquid vis-à-vis a molecular diluent for a tripodal TREN-based diglycolamide ligand (DGA-TREN) vs. a tripodal diglycolamide ligand (T-DGA) which may have great significance in radioactive waste remediation. The nature of the bonding to Eu3+ ion was investigated by EXAFS as well as by DFT calculations. [ABSTRACT FROM AUTHOR]

Tight glycemic control is now an imperative of outpatient diabetes care. The inpatient arena remains under the influence of an ineffective paradigm characterized by tolerance for hyperglycemia and a reluctance to use insulin intensively. This article is a call to action against the lip service paid to inpatient diabetes care. The compelling in vitro and in vivo evidence for the benefit of intensive insulin-mediated glycemic control is summarized. The linchpin of current inpatient care is a commonly used insulin sliding scale. This autopilot approach as the sole mode of treatment for inpatient hyperglycemia has been strongly condemned. Nevertheless, it continues to survive. The evidence supports the compelling argument that the adverse effect of hyperglycemia on hospital length of stay, morbidity, and mortality is substantial. Clinicians, nurses, administrators, and insurers ought to look critically at the prevailing paradigm and spearhead the much-needed revolution in inpatient diabetology. The issue of glycemic targets, the need for noninvasive blood glucose monitoring, and the role of nursing staff in this revolution are raised. We call for the banning of the insulin sliding scale use as the sole diabetes order. Also, the use of basal insulin via continuous intravenous insulin infusion or subcutaneous insulin analogs should be embraced. Educating nurses, house staff, and other frontline professionals in the adverse consequences of the current paradigm is essential. Inpatient glycemic control matters; clinical and financial outcomes are at stake. It behooves the health care system and the diabetic public to address the contemporary state of inpatient diabetology as soon as possible. J GEN INTERN MED 2004;19:466 – 471. [ABSTRACT FROM AUTHOR]

AgBiO 3 is reported for the exclusive oxidation of Am 3+ → AmO 2 + at near-neutral pH conditions. Literature methods of AmO 2 + generation are generally two-step processes; i.e. , Am 3+ → AmO 2 2+ oxidation followed by AmO 2 2+ → AmO 2 + reduction. These methods for Am 3+ → AmO 2 + oxidation use high temperatures (80-100 °C) and/or several reagents, causing the in situ presence of the AmO 2 + -complex rather than the AmO 2 + aq ions. This not only interferes with the much-needed Am-Cm selectivity but also limits the use of AmO 2 + aq in any other experimental study. The single-step Am 3+ → AmO 2 + oxidation in the present work using AgBiO 3 is done at 25 °C in a non-complexing medium at pH ∼4, making it a first-of-its-kind report. Am-Eu and Am-Cm separation in a single contact, with a separation factor >10 4 , was achieved using the present method, which is unprecedented among aqueous feed solutions. The AmO 2 + generated using the present method under non-complexing pH conditions makes it also suitable for exploring the fundamental chemistry of the higher valent americyl ion. A complexation study using the thus-generated AmO 2 + ion with acetate ion supports the concept.

A novel tripodal diglycolamide ligand containing a triazamacrocycle center (2,2',2''-(((1,4,7-triazonane-1,4,7-triyl)tris(2-oxoethane-2,1-diyl)) tris(oxy)) tris( N, N-dioctylacetamide), abbreviated as T9C3ODGA) was synthesized and characterized by conventional techniques. The ligand resulted in efficient extraction of actinide/lanthanide ions yielding the trend: Eu 3+ > Pu 4+ > Am 3+ > NpO 2 2+ > UO 2 2+ > Sr 2+ > Cs + . Similar to most of the other diglycolamide (DGA) ligands, Eu 3+ was preferentially extracted as compared to Am 3+ ; the separation factor ( D Eu / D Am ) value at 3 M HNO 3 was ca. 4.2. In contrast, separation from UO 2 2+ ion was less effective as compared to that of other tripodal DGA ligands studied earlier. Solvent extraction studies indicated extraction of species of the ML 2 (where L is T9C3ODGA) stoichiometry. The formation of an inclusion complex with no inner-sphere water molecule was confirmed from luminescence spectral studies. DFT computations predicted the presence of an inner-sphere nitrate ion in the most preferred complex, which was also supplemented by EXAFS and luminescence studies. The selectivity of T9C3ODGA could be explained on the basis of its more favorable interactions with Eu 3+ as compared to those with Am 3+ both in the gas and the solution phases.

This paper reports the solvent extraction of Am 3+ and Eu 3+ using N,N,N',N',N'',N''-hexa-n-octylnitrilotriacetamide (HONTA) as the extractant in n-dodecane. The results are in variance with those reported previously with respect to the nature of the extracted species. The solvent extraction data were entirely different from those reported previously as the extracted species conformed to 1 : 2 (M : L) species for both Am 3+ and Eu 3+ ions. The structure of the extracted complex was determined by EXAFS demonstrating the three amidic 'O' atoms of the HONTA complex with the Eu 3+ ion. In the case of the Am 3+ ion, the pivotal 'N' atom is suggested to bond to the metal ion, which may explain the significantly more favourable extraction of Am 3+ vis-à-vis Eu 3+ . The absence of H 2 O molecules in the inner coordination sphere of the Eu 3+ -HONTA extract was confirmed by luminescence spectroscopic measurements. Complexation studies in MeOH and EtOH indicated the formation of both 1 : 1 and 1 : 2 complexes with Nd 3+ ions. The results are explained on the basis of DFT calculations using HMNTA, the corresponding hexamethyl analogue of HONTA.