Search results for "uranyl"
showing 10 items of 47 documents
Interactions of Dioxouranium(VI) with Amines in Aqueous Solution
2010
The interaction of the dioxouranium(VI) ion with five low molecular weight polyamines (ethylenediamine, putrescine, cadaverine, spermidine, and spermine) and with poly(allyl)amine (15 kDa) was studied potentiometrically (ISE-H + glass electrode) at T ) 298.15 K. Investigations were carried out in NaNO3 ionic medium, at I ) 0.1 mol · L -1 (and 0.5 mol · L -1 for poly(allyl)amine only), in the pH range 3.5 to 5.5, before the formation of uranyl insoluble species. The results gave evidence for the formation of two species, namely, UO2L 2+ and UO2L(OH) + for the diamine systems (ethylenediamine, putrescine, cadaverine), UO2L 2+ and UO2LH 3+ for spermidine, and UO2LH 3+ and UO2LH2 4+ for spermin…
Extraction of uranyl ions from aqueous solutions using silica-gel-bound macrocycles for alpha contaminated waste water treatment
2004
Abstract The efficiency for the extraction of U(VI) of new modified silica gels, namely N-tripropionate (or N-triacetate)-substituted tetraazamacrocycles-bound silica gels, has been studied. The effect of the nature of the ligand, the pH and the temperature was studied both in batch experiments as well as in continuous extraction. These silica gels are good candidates for the extraction of U(VI) when compared to a commercially available acid-type chelating resin. The breakthrough and regeneration tests showed that the total removal of U(VI) from a contaminated solution can be achieved by using a column packed with such tetraazamacrocycles-bound silica gels. Finally, the use of a modified si…
Specific recognition of fluoride anion using a metallamacrocycle incorporating a uranyl-salen unit
2008
The design and synthesis of a novel fluoride receptor that uses a salen-complexed Lewis acidic uranyl center as the sole binding site is reported here. This receptor binds fluoride anions in DMSO with a high affinity constant (K > 106 M-1) and exhibits a negligible affinity (K < 10 M-1) towards otherwise effective competitors, such as acetate, phosphate and cyanide anions.
Effects of preorganization in the chelation of UO22+ by hydroxamate ligands: cyclic PIPO– vs linear NMA–
2018
International audience; Many siderophores incorporate as bidentate chelating subunits linear and more seldomly cyclic hydroxamate groups. In this work, a comparative study of the uranyl binding properties in aqueous solution of two monohydroxamic acids, the prototypical linear N-methylacetohydroxamic acid (NMAH) and the cyclic analog 1-hydroxypiperidine-2-one (PIPOH), has been carried out. The complex [UO2(PIPO)(2)(H2O)] crystallized from slightly acidic water solutions (pH < 5), and its molecular structure was determined by X-ray diffraction. The uranyl speciation in the presence of both ligands has been thoroughly investigated in a 0.1 M KNO3 medium at 298.2 K by the combined use of four …
Alkaline hydrolysis/methylation-acetylation: a new technique for ultrastructural DNA cytochemistry.
1991
SUMMARY A new technique for the visualization of DNA-containing structures in electron microscopy is described. Samples of glutaraldehyde-fixed bone marrow from rats were subjected to alkaline hydrolysis to remove RNA and the phosphate of phospho-proteins, followed by a combined blockage of protein carboxyl and amino groups through methylation-acetylation. After uranyl acetate staining of epoxy-embedded ultrathin sections, chromatin from all cell types showed a highly selective and intense electron opacity. Staining methods for DNA were also positive in semithin sections. This simple procedure could be very useful in ultrastructural cytochemistry of DNA and chromatin.
Predicting the Breakthrough of Ternary Ca–Uranyl–Carbonate Species in Mineral Water Treated by a Fixed-Bed Granular Ferric Hydroxide Adsorbent
2020
A CD-MUSIC surface complexation model was set up on the basis of batch equilibrium experiments with uranyl ions and akaganeite-based granular ferric hydroxide (GFH), which is often used in water pu...
Complex Formation of the Uranyl (UO22+) Ion with the Diethylene Triaminopentaacetate (DTPA) Ligand at 25 °C in 3 M Sodium Perchlorate
2011
The complex formation between the uranyl (UO22+) ion and the diethylene triaminopentaacetate ligand (DTPA) has been investigated at 25 °C, in a 3 M sodium perchlorate medium. The overall protonation constants βjH of the free ligand have been previously determined in this ionic medium: six protonated species (HjA), with j ranging from 1 to 6, together with the free anion A5− have been identified in the concentration range from (3·10−3 to 13·10−3) mol·kg−1. Four complex species, H2UO2A−, HUO2A2−, UO2A3−, and UO2AOH4−, have been identified in the total uranyl concentration range from (1.1·10−3 to 5.7·10−3) mol·kg−1, and their overall stability constants determined, keeping the metal to ligand …
Mixed complexes of alkaline earth uranyl cabonates: A laser-induced time-resolved fluorescence spectroscopic study
2008
The interaction of the alkaline earth ions Mg2+, Sr2+ and Ba2+ with the uranyl tricarbonate complex has been studied by time resolved laser-induced fluorescence spectroscopy. In contrast to the non-luminescent uranyl tricarbonate complex the formed products show slight luminescence properties. These have been used to determine the stoichiometry and complex stabilities of the formed compounds. As the alkaline earth elements are located in an outer shell of the complex the influence of the type of the alkaline earth element on the stability constant is not very drastic. Therefore all obtained data were averaged in order to derive an common stability constant for the described complexes. These…
Influence of saline and pH on collagen type I fibrillogenesis in vitro: Fibril polymorphism and colloidal gold labelling
2007
We have produced different collagen type I fibrils by in vitro fibrillogenesis of acetic acid-soluble collagen within the pH range 2.5-9.0, in the presence and absence of 150 mM NaCl. The varying relatively stable molecular assemblies and polymorphic fibrillar end-products produced after 24 h incubation have been assessed and compared by the TEM study of specimens negatively stained with uranyl acetate. In the presence of 150 mM NaCl, the assembly of collagen at low pH (2.5) leads to the formation of initial molecular aggregates that progressively link together at slightly higher pH (5.0) to form sub-fibrils and spindle-shaped D-banded bundles of sub-fibrils. At pH 6.0 these D-banded bundle…