Showing papers in "Radiochimica Acta in 2014"
TL;DR: In this article, a batch experiment and high resolution EXAFS technique with bent crystal analyzer were combined to study Eu(III) retention mechanisms on beta-MnO2 as a function of various environmental factors.
Abstract: The batch experiment and high resolution EXAFS technique with bent crystal analyzer were combined to study Eu(III) retention mechanisms on beta-MnO2 as a function of various environmental factors. The results indicated that the sorption of Eu(III) onto beta-MnO2 was obviously dependent on pH but independent of ionic strength, suggesting the formation of inner-sphere surface complexes. Results of high resolution EXAFS analysis showed that Eu was surrounded by 8 +/- 1 O atoms in the first shell at REu-O approximate to 2.40 angstrom for all sorption samples. A second shell of Mn atoms at REu-Mn approximate to 3.78 angstrom was observed for all sorption samples, which was associated with the formation of a bidendate inner-sphere complex with chemical bonding via edge sharing to MnO6-octahedron. This study shows the utility of high resolution EXAFS technique with bent crystal analyzer to discriminate the fluorescence peak of Eu(III) from that of manganese hydroxides, whose fluorescence peaks are too close in energy to be discriminated by the conventional EXAFS technique with a low resolving solid-state detector. Both the macroscopic interaction data and the molecular level evidence of Eu(III) surface speciation at the oxide-water interface should be factored into better evaluation of Eu(III) and related radionuclide mobility in the natural environment.
61 citations
TL;DR: The MARS beamline at the SOLEIL synchrotron as mentioned in this paper is dedicated to the characterization of radioactive material samples and is optimized for X-ray absorption spectroscopy techniques (XANES/EXAFS), powder diffraction (XRD) but x-ray fluorescence (XRF) analysis, High Energy Resolution Fluorescence Detected -XAS (HERFD-XAS) and μ -Xas/XRD are also possible.
Abstract: The MARS beamline at the SOLEIL synchrotron is dedicated to the characterization of radioactive material samples. One great advantage of the beamline is the possibility to characterize about 380 radionuclides by different X-ray techniques in the same place. This facility is unique in Europe. A wide energy range from around 3.5 keV to 36 keV K-edges from K to Cs, and L3 edges from Cd to Am and beyond can be used. The MARS beamline is optimized for X-ray absorption spectroscopy techniques (XANES/EXAFS), powder diffraction (XRD) but x-ray fluorescence (XRF) analysis, High Energy Resolution Fluorescence Detected -XAS (HERFD-XAS), X-ray Emission (XES) and μ -XAS/XRD are also possible. A description of the beamline as well as its performances are given in a first part. Then some scientific examples of XAS studies from users are presented which cover a wide variety of topics in radiochemistry and nuclear materials.
45 citations
TL;DR: In this paper, the adsorption and sequen- tial desorption of U(VI) on Al-FeOOHs were conducted by batch techniques under N2 conditions.
Abstract: Aluminum co-precipitated with goethites (Al- FeOOHs) are ubiquitous within (sub)-surface environ- ments, which are considered one of the most important sinks for radionuclide pollution management. Accord- ingly, various mole ratios Al-FeOOH were synthesized and characterized by XRD, FT-IR, TEM, specific surface area and potentiometric acid-base titration. According to XRD and TEM images, the morphology of Al-FeOOH was trans- formed from acicular-like goethite to cotton-like gibbsite with increasing Al content. The adsorption and sequen- tial desorption of U(VI) on Al-FeOOHs were conducted by batch techniques under N2 conditions. The batch adsorp- tion results showed that the adsorption of U(VI) on Al- FeOOHs slightly increased at pH 8.0 was due to the electrostatic repulsion between negative charge surface and negative carbonato-complexes. The adsorption of U(VI) on Al-FeOOHs was independent of ionic strength at pH > 5.0, indicating that the inner-sphere surface complexation predominated their adsorption be- haviors, whereas U(VI) adsorption on Al-FeOOH could be the outer-sphere surface/cation exchange reaction. The se- quential extraction texts showed that the desorption of U(VI) from Al-FeOOHs decreased with increasing Al con- tent. These findings highlighted the effect of Al content on the sequestration and immobilization of U(VI) onto Al-FeOOHs from (sub)-surface environments in pollution management.
41 citations
TL;DR: In this article, the authors used the Gaines-Thomas convention to calculate the selectivity coefficients for Cs/K, cs/Na, and ccs/Ca ion exchange reactions.
Abstract: Abstract For the modeling of cesium sorption on biotite, samples of natural biotite separated from gneissic rocks were converted into monoionic potassium, sodium, and calcium forms, and sorption isotherms for Cs/K, Cs/Na and Cs/Ca exchange were determined at pH 6 and 8 in E-4–E-8 M Cs solutions. Selectivity coefficients for Cs/K, Cs/Na, and Cs/Ca ion exchange reactions were calculated from the isotherm data, using the Gaines-Thomas convention. At Cs loadings below 1% of the total ion exchange capacity, the overall selectivity coefficient for Cs/Ca exchange was approximately five and seven orders of magnitude higher than those for Cs/Na and Cs/K exchange, respectively. Based on the selectivity coefficients, the ion exchange isotherms were modeled with the U.S. Geological Survey PhreeqC program, assuming three different types of ion exchange site: sites on the basal planes on biotite crystal surfaces with 95% site abundance, probable interlayer sites on crystal edges [frayed edge sites (FESs)] (0.02%) and third-type sites (5%), the physical background of which is unclear. Of these three types, the FES sites were superior in Cs selectivity, while the planar sites exhibited the lowest selectivity, and the third-type sites had selectivity between these two. The functionality of the model was successfully verified by modeling the Cs sorption isotherms on crushed mica gneiss rock in saline groundwater. Determination of the exchangeable ions K, Na, Ca, and Cs on the basal plane and edge surfaces by scanning electron microscopy-energy-dispersive x-ray spectroscopy (SEM-EDX) supports the results of modeling: edge sites highly prefer Cs ions and also Ca and Na ions but not K ions.
39 citations
TL;DR: In this article, groundwaters were sampled from two districts (Bathinda and Mansa) of Punjab state and analyzed for their major ionic concentrations and uranium isotope compositions to assess the possible origins of the waters and water-rock interactions that occurred in the deep aquifer system.
Abstract: Abstract Groundwaters (borewell and handpump) were sampled from two districts (Bathinda and Mansa) of Punjab state and analyzed for their major ionic concentrations and uranium isotope compositions in order to assess the possible origins of the waters and water–rock interactions that occurred in the deep aquifer system. The major ionic concentrations of waters were plotted on a Piper diagram and grouped into four dominant hydrochemical facies as (Na+K)-SO4+Cl type (69% – 73%), (Ca+Mg)-SO4+Cl type (6% – 21%), (Ca+Mg)–HCO3 type (4% – 6%) and (Na+K)-HCO3 type (2% – 19%). It was observed that mobility of uranium in groundwater was very much influenced by TDS (total dissolved solids). To investigate the various mechanisms for deriving the elevated uranium concentrations in groundwater, 234U/238U activity ratios (ARs) were calculated using the determined activity levels of 234U and 238U. The mean ARs was found to be near unity (i.e. secular equilibrium) in the study regions confirmed that uranium in groundwaters was mainly resulted from its host/parent rocks through weathering processes. The concentration of HCO3− in ground water showed one order of magnitude higher than the total dissolved SiO2 indicates that carbonate weathering was the dominant process due to major water–rock interaction. The uranium speciation in groundwaters was investigated by an equilibrium model calculation using MEDUSA (make equilibrium diagrams using sophisticated algorithms) under the influence of redox conditions and complexant concentration. At the observed range of pH values, the predominant redox speciation of uranium was observed as hydroxo-carbonato complexes of (UO2)2(CO3)(OH)3− and hydroxyl complexes of UO2(OH)3− which might be caused for increasing the solubility of uranium. Due to very low concentration of phosphate in groundwater, its effects on U(VI)-aqueous speciation was negligible.
34 citations
TL;DR: In this article, tritium labeling was introduced into detonation nanodiamonds (ND) through the Tritium thermal activation method and two target preparation techniques were developed to increase the radioactivity and the specific radioactivity of the labeled product: the desiccation of the waterless solvent suspension and the lyophilization of the hydrosol.
Abstract: Abstract Tritium labeling was introduced into detonation nanodiamonds (ND) through the tritium thermal activation method. Two target preparation techniques were developed to increase the radioactivity and the specific radioactivity of the labeled product: the desiccation of the waterless solvent suspension and the lyophilization of the hydrosol. The specific radioactivity of the labeled product was shown to correlate with the hydrogen content in the starting material and to achieve 2.6 TBq/g.
31 citations
TL;DR: In this paper, the authors revisited the sorption of actinides in different valence states (Am(III), Th(IV), Np(V) and U(VI) onto hematite with the special emphasis on the equilibrium constants of formation of surface species.
Abstract: Abstract The sorption of actinides in different valence states – Am(III), Th(IV), Np(V) and U(VI) onto hematite have been revisited with the special emphasis on the equilibrium constants of formation of surface species. The experimental sorption data have been treated using surface complexation modeling from which the set of new values of equilibrium constants were obtained. Formation of inner sphere monodentate surface species adequately describes the pH-sorption edges for actinide ions indicative the ionic electrostatic nature of bonding with small or no covalency contribution. The linear free energy relationship representing the correlation between the hydrolysis constants and surface complexation constants has been developed for various cations including K(I), Li(I), Na(I), Ag(I), Tl(I), Sr(II), Cu(II), Co(II), La(III), Eu(III), Ga(III), Am(III), Th(IV), Np(V), U(VI).
27 citations
TL;DR: In this article, the in-situ synthesis of metal carbonyl complexes with short-lived isotopes of transition metals was studied, showing that these start to decompose at temperatures above 300 ℃ in contact with a quartz surface.
Abstract: Abstract We report on the in-situ synthesis of metal carbonyl complexes with short-lived isotopes of transition metals. Complexes of molybdenum, technetium, ruthenium and rhodium were synthesized by thermalisation of products of neutron-induced fission of 249Cf in a carbon monoxide-nitrogen mixture. Complexes of tungsten, rhenium, osmium, and iridium were synthesized by thermalizing short-lived isotopes produced in 24Mg-induced fusion evaporation reactions in a carbon monoxide containing atmosphere. The chemical reactions took place at ambient temperature and pressure conditions. The complexes were rapidly transported in a gas stream to collection setups or gas phase chromatography devices. The physisorption of the complexes on Au and SiO2 surfaces was studied. We also studied the stability of some of the complexes, showing that these start to decompose at temperatures above 300 ℃ in contact with a quartz surface. Our studies lay a basis for the investigation of such complexes with transactinides.
27 citations
TL;DR: In this article, rapid simultaneous removal of cobalt, strontium and cesium from microcrystalline naphthalene as solid-phase ex- tractant was investigated.
Abstract: Most of the procedures developed for the extrac- tion of cobalt, strontium and cesium by solid phase extrac- tion do not employ simultaneous extraction of them. In this study, rapid simultaneous removal of Co 2+ , Sr 2+ and Cs + on microcrystalline naphthalene as solid-phase ex- tractant was investigated. These ions were allowed to form chelates with oxine and then adsorbed on freshly micro- crystalline naphthalene from aqueous solutions. The solid phase extraction procedure (SPE) was optimized by using model solution containing Co 2+ , Sr 2+ and Cs + in batch system. The effects of different parameters such as varia- tion in pH, reagent concentration, standing time, naphtha- lene solution concentration and contact time on the simul- taneous removal of these ions was studied. The obtained results indicated that, sorption was found to be rapid, and the percentage removal ofCo 2+ , Sr 2+ and Cs + was found to be 98, 79 and 68% within 10 min, respectively. The kinet- ics of the sorption process was investigated to understand the kinetic characteristics of sorption of metal chelates onto microcrystalline naphthalene. The developed proce- dure has been successfully applied to the removal and re- covery of 60 Co and 134 Cs from liquid radioactive waste.
27 citations
TL;DR: In this article, two proton activation experiments utilizing the stacked foil technique between 40 and 200 MeV were employed to study the likely co-formation of radionuclides expected to be especially challenging to separate from 225Ac.
Abstract: Abstract Accelerator production of 225Ac addresses the global supply deficiency currently inhibiting clinical trials from establishing 225Ac's therapeutic utility, provided that the accelerator product is of sufficient radionuclidic purity for patient use. Two proton activation experiments utilizing the stacked foil technique between 40 and 200 MeV were employed to study the likely co-formation of radionuclides expected to be especially challenging to separate from 225Ac. Foils were assayed by nondestructive γ-spectroscopy and by α-spectroscopy of chemically processed target material. Nuclear formation cross sections for the radionuclides 226Ac and 227Ac as well as lower lanthanide radioisotopes 139Ce, 141Ce, 143Ce, and 140La whose elemental ionic radii closely match that of actinium were measured and are reported. The predictions of the latest MCNP6 event generators are compared with measured data, as they permit estimation of the formation rates of other radionuclides whose decay emissions are not clearly discerned in the complex spectra collected from 232Th(p,x) fission product mixtures.
26 citations
TL;DR: In this article, the authors present 90 Nb, a radionuclide with a half-life of 14.6 h that allows visualizing and visualizing its properties.
Abstract: Fast progressing immuno-PET asks to explore new radionuclides. One of the promising candidates is 90 Nb. It has a half-life of 14.6 h that allows visualizing
TL;DR: In this article, the surface chemistry of alloyed uranium (U-Nb and U-Ti) in hydrogen atmosphere is reported, and it is revealed that the hydrating nucleation and subsequent growth of Alloyed uranium are closely connected with the surface states, underlying metal matrix, and microstructure-dependent.
Abstract: Abstract Uranium is very important in nuclear energy industry; however, uranium and its alloys corrode seriously in various atmospheres because of their chemical reactivities. In China, continuous investigations focused on surface chemistry have been carried out for a thorough understanding of uranium in order to provide technical support for its engineering applications. Oxidation kinetics of uranium and its alloys in oxidizing atmospheres are in good agreement with those in the literature. In addition to the traditional techniques, non-traditional methods have been applied for oxidation kinetics of uranium, and it has been verified that spectroscopic ellipsometry and X-ray diffraction are effective and nondestructive tools for in situ kinetic studies. The inhibition efficiency of oxidizing gas impurities on uranium hydrogenation is found to follow the order CO2 > CO > O2, and the broadening of XPS shoulders with temperature in depth profile of hydrogenated uranium surface is discussed, which is not mentioned in the literature. Significant progress on surface chemistry of alloyed uranium (U-Nb and U-Ti) in hydrogen atmosphere is reported, and it is revealed that the hydrating nucleation and subsequent growth of alloyed uranium are closely connected with the surface states, underlying metal matrix, and it is microstructure-dependent. In this review, the recent advances in uranium surface chemistry in China, published so far mostly in Chinese language, are briefly summarized. Suggestions for further study are made.
TL;DR: Wang et al. as discussed by the authors used trialkylphosphine oxide (TRPO) with a single functional group to partition tri-, tetra-and hexa-valent actinides.
Abstract: Abstract In the last decades, the separation of actinides was widely and continuously studied in China. A few kinds of salt-free reductants to adjust Pu and Np valences have been investigated. N, N-dimethylhydroxylamine is a good reductant with high reduction rate constants for the co-reduction of Pu(IV) and Np(VI), and monomethylhydrazine is a simple compound for the individual reduction of Np(VI). Advanced PUREX based on Organic Reductants (APOR) was proposed. Trialkylphosphine oxide (TRPO) with a single functional group was found to possess strong affinity to tri-, tetra- and hexa-valent actinides. TRPO process has been first explored in China for actinides partitioning from high level waste and the good partitioning performance was demonstrated by the hot test. High extraction selectivity for trivalent actinides over lanthanides by dialkyldithiophosphinic acids was originally found in China. A separation process based on purified Cyanex 301 for the separation of Am from lanthanides was presented and successfully tested in a battery of miniature centrifugal contactors.
TL;DR: In this paper, the recommended cross section data of IAEA for production of 111In and 114mIn through the 112Cd(p,2n) and 114Cd (p,n) reactions new measurements were performed.
Abstract: Abstract In order to update the recommended cross section data of IAEA for production of 111In and 114mIn through the 112Cd(p,2n) and 114Cd(p,n) reactions new measurements were performed. In stacked-foil irradiations with incident proton energy of 36.7 and 25 MeV on highly enriched 112Cd and 114Cd targets, the excitation functions for 109,110g,110m,111,113m,114mIn were determined, relative to the monitor reactions natCu(p,x)62,65Zn. The results are compared with the available literature values (also extracted from measurements on natCd) and with data listed in the on-line library TENDL-2012 (calculated with the TALYS 1.4 theoretical code). The industrial, PC-controlled automated dissolution and separation chemistry apparatus for delivery of large quantities of nca 111In and the recovery of enriched 112Cd from processed irradiated targets are described.
TL;DR: In this article, a 1.1 M solution of tri-iso-amyl phosphate (TiAP) in n-dodecane (n-DD) from uranyl nitrate solutions in nitric acid media has been investigated as a function of metal loading and equilibrium aqueous phase acidity at 303 K.
Abstract: Abstract Batch extraction of U(VI) by 1.1 M solution of tri-iso-amyl phosphate (TiAP) in n-dodecane (n-DD) from uranyl nitrate solutions in nitric acid media has been investigated as a function of metal loading and equilibrium aqueous phase acidity at 303 K. A method adopted for free acidity determination by using a mixture of potassium oxalate and sodium fluoride for complexing U(VI) has been validated by comparing the data generated in the present study with literature data available for tri-n-butyl phosphate (TBP) under identical conditions. Extraction and stripping behaviour of 1.1 M TiAP/n-DD-U(VI)/HNO3 and 1.1 M TBP/n-DD-U(VI)/HNO3 systems have been compared by carrying out extraction, scrubbing and a series of stripping in cross-current mode. Stripping behaviour of both the solvents loaded with U(VI) and HNO3 has also been investigated as a function of time to understand the effects of nitric acid induced degradation on stripping.
TL;DR: In this article, the authors used room-temperature ionic liquids (RTILs) as solvent alternatives for possible application in spent fuel reprocessing, particularly in the extraction of metal ions from high-level radioactive aqueous waste, due to their unique physical and chemical properties.
Abstract: Room-temperature ionic liquids (RTILs) have recently received increasing attention as solvent alternatives for possible application in spent fuel reprocessing, particularly in the extraction of metal ions from high-level radioactive aqueous waste, due to their unique physical and chemical properties. Herein, the solvent extraction of the uranyl ions (UO22+) was performed using N,N'-diethyl-N,N'-di(para)tolyl-dipicolinamide (Et((p))TDPA) as the extractant in a commonly used ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([C(4)mim][PF6]). The effects of vortexing time, phase ratio and the concentration dependence of Et-(p) TDPA, nitric acid and sodium nitrate on the extraction were studied in detail. The extraction mechanism was deduced based on the slope analysis and UV-vis measurement. The distribution ratio of U from 3 mol/L nitric acid by 0.3 mol/L EtTDPA/C-4 mim PF6 is found to be almost 100. Conventional log-log plot analysis of the extraction equilibrium data suggests that the ions are extracted as a complex in 2 : 3 ratio of UO22+ to extractant, and the extraction most likely occurs by a cation-exchange mode since the concentration of C(4)mim(+) in the aqueous phase increases linearly with the percent extraction of UO22+ evidenced by UV-vis measurement. This work promises to provide new efficient media based on RTILs for separation of uranium from the radioactive aqueous waste.
TL;DR: In this article, the third phase formation behavior of nitric acid and neodymium(III) in 0.1m-M UDGA/n-dodecane was studied and the stoichiometry of Am(III)-UDGA was determined from the slope analysis of the extraction data.
Abstract: Abstract New unsymmetrical diglycolamides (UDGAs), N, N-di-butyl-N′, N′-di-dodecyl-3-oxapentane-1,5-diamide (C12-C4), N, N-di-dodecyl-N′, N′-di-hexyl-3-oxapentane-1,5-diamide (C12-C6), N, N-di-decyl-N′, N′-di-dodecyl-3-oxapentane-1,5-diamide (C12-C10) have been synthesized, and evaluated for the separation of americium(III) and europium(III) from nitric acid medium. The extraction behavior of Am(III), Eu(III), and Sr(II) in a solution of these UDGAs in n-dodecane was studied as a function of concentration of nitric acid in the aqueous phase. The distribution ratio of Am(III) and Eu(III) increased with increase in the concentration of nitric acid. The third phase formation behavior of nitric acid and neodymium(III) in 0.1 M UDGA/n-dodecane was studied. The third phase formation was not observed in all these UDGAs in n-dodecane (0.1 M), when the concentration of Nd(III) was ∼ 500 mM in 3–4 M nitric acid. The stoichiometry of Am(III)-UDGA was determined from the slope analysis of the extraction data, which indicated the formation of 1:3 complex in all cases. Our studies revealed that the UDGA ligands with dodecyl group attached to one amidic nitrogen atom is inevitable for preventing third phase formation and the alkyl group at the other amidic nitrogen can be varied from butyl to decyl group for obtaining efficient extraction of trivalent actinides from high-level nuclear waste.
TL;DR: In this article, the complexation properties of 2,9-bis(dialkyl-1,2,4-triazin-3-yl)-1,10-phenanthrolines (BTPhens) have been calculated by density functional theory coupled with relativistic small-core pseudopotential.
Abstract: The complexation properties of Am(III) and Eu(III) with a serial of novel N-heterocyclic tetradentate ligands, 2,9-bis(dialkyl-1,2,4-triazin-3-yl)-1,10-phenanthrolines (BTPhens), have been calculated by density functional theory (DFT) coupled with relativistic small-core pseudopotential. It is found that the nitrogen atoms in triazine rings favor metal cations more than those in phenanthroline skeleton. The Am-N bond lengths are comparable to or even shorter than those of Eu-N bonds based on the larger radii of Am(III) than Eu(III). The effect of alkyl substituents on the complex structures is limited but they can adjust the complexation reaction and extraction kinetics. Additionally, the solvent effect can decrease the probability of the complexation reactions greatly and the solvation energies of Am(III) and Eu(III) might be the primary driving force in the complexation selectivity. The complexation reactions for forming ML(NO3)(3) and [ML2 (NO3)](2+) complexes are believed to dominate the selective extraction separation of Am(III) from Eu(III) in nitric acid media, which agrees well with the experimental results. The comparisons of BTPhens with BTBPs in dipoles and electronic structures confirm that the BTPhens exhibit more favourable extraction kinetics and selectivity for minor actinides.
TL;DR: In this paper, the authors investigated the chemical behavior of Np in aqueous nitric acid solution containing Tc(VII), U(IV), hydrazine, Pu and Tc, which coexist in U/Pu separation stage of PUREX process.
Abstract: Abstract The chemical behavior of Np is influenced by many factors, such as U(IV), hydrazine, Pu and Tc, which coexist in U/Pu separation stage of PUREX process. Firstly, the reduction of Np(V) to Np(IV) by Tc(IV) was studied in nitric acid media, and the rate equation could be expressed as − d[Np(V)]/dt = k[Np(V)][Tc(IV)]0.8[HNO3]1.2, k = 28.5 ± 0.9 (L/mol)2/min at 25 ℃, the activation energy was Ea = 70.0 kJ/mol. Thereafter, the chemical behavior of Np was investigated in aqueous nitric acid solution containing Tc(VII), U(IV) and N2H4. Np(V) was reduced to Np(IV) quickly, Tc(VII) was reduced to Tc(IV) and U(IV) was oxidized to U(VI) at the same time. Thereafter Np(IV) was entirely reoxidized to Np(V) when U(IV) and hydrazine were completely consumed. The fast reduction of Np(V) was mainly ascribed to Tc(IV). In addition, Tc(VII) and nitric acid had little influence on the fast oxidation of Np(IV).
TL;DR: In this article, the stability constants describing Pu(IV, Th(IV), and Np(V) binding to Leonardite humic acid (HA) were determined using a discrete pKa model.
Abstract: Abstract In this work stability constants describing Pu(IV), Th(IV), and Np(V) binding to Leonardite humic acid (HA) were determined using a discrete pKa model. A hybrid ultra-filtration/equilibrium dialysis, ligand exchange technique was used to generate the partitioning data. Ethylenediaminetetraacetic acid (EDTA) was used as a reference ligand to allow the aqueous chemistry of the Pu(IV)-HA system to be examined over a range of pH values, while minimizing the possibility of precipitation of Pu(IV). The conditional stability constant for Pu(IV) complexation with HA determined as part of this work is log β112 = 6.76 ± 0.14 based on the equation: Pu4+ + HL3 + 2H2O ↔ Pu(OH)2L3+ + 3H+ where HA is represented by HL3 (a binding site on the HA with a pKa value of 7). This value is three orders of magnitude higher than the Th(IV)-HA constant and between six and eight orders of magnitude higher than the Np(V)-HA complex. The magnitude of the stability constants and the general trend of increasing complexation strength with increasing pH is consistent with previous observations. The Pu(IV)-HA stability constants were used to model sorption of Pu(IV) to gibbsite in the presence of HA. Assuming only aqueous Pu-HA complexes and AlOH-Pu surface complexes, the model was unable to predict the observed data which exhibited greater sorption at pH 4 relative to pH 6; a phenomenon which does not occur in the absence of HA. Therefore, this study demonstrates that ternary Pu-HA-gibbsite complexes may form under low pH conditions and exhibit greater sorption than that observed in the absence of HA. Although the presence of HA may increase the solubility/aqueous concentrations of Pu in the absence of a solid phase, formation of ternary complexes may indeed retard the subsurface migration of Pu. The corollary to this finding is that increased mobility may occur if the ternary surface complex forms on a mobile colloid rather than part of the subsurface matrix
TL;DR: In this article, the interactions among Eu(III), humic acid (HA), and Al2O3 as a function of pH and ionic strength were investigated by batch technique and extended X-ray absorption fine structure (EXAFS) analy- sis.
Abstract: In this study, the interactions among Eu(III), humic acid (HA) and �� -Al2O3 as a function of pH and ionic strength were investigated by batch technique and extended X-ray absorption fine structure (EXAFS) analy- sis. For binary �� -Al2O3/Eu(III) systems, the pH-dependent and ionic strength-independent sorption behavior was indicative of an inner-sphere complexation mechanism. The EXAFS spectra analysis showed that Eu(III) sorption mechanisms at pH 5.0, 6.5 and 8.0 could be attributed to the formation of edge-shared and corner-shared surface complexes. In contrast, surface precipitation and/or sur- face polymerization tended to be the predominant sorp- tion mechanism at pH 10.0. The spectra analysis results suggested no difference between the proportions of edge- shared and corner-shared complexes formed at different ionic strengths. For ternary �� -Al2O3/HA/Eu(III) systems, the sorption percentage of Eu(III) increased with increas- ing ionic strength. The EXAFS-derived structural param- eters pointed to the formation of binary surface com- plexes (i.e., edge-shared mode and corner-shared mode) at low ionic strength and ligand-bridging ternary complexes at high ionic strength. In addition, the stoichiometry of ternary complexes showed a trend from 1:1 form (i.e., �� - Al 2 O 3 /L/Eu(III), L represents HA sites) to 1:2 form (i.e., �� -Al 2 O 3 /L 2 /Eu(III), L represents HA sites) with increasing ionic strength. The experimental findings in this study can provide an important theoretical basis for further predict- ing the fate of trivalent radionuclides in aquatic systems.
TL;DR: In this article, the authors measured the integral cross sections of the 64Zn(n, p)64Cu and 67Zn (n, ǫp)67Cu reactions for the fast neutron spectrum of TRIGA Mark-II reactor at Savar, Dhaka, Bangladesh.
Abstract: Abstract Integral cross sections of the 64Zn(n, p)64Cu and 67Zn(n, p)67Cu reactions were measured for the fast neutron spectrum of TRIGA Mark-II reactor at Savar, Dhaka, Bangladesh. A clean radiochemical separation was performed to isolate the copper radionuclides from the target element zinc. The radioactivities produced in the irradiation were measured by HPGe γ-ray spectroscopy. The neutron flux over the energy range 0.5–20 MeV was determined using the 58Ni(n, p)58Co monitor reaction. The measured results amount to 28.9 ± 2.0 mb and 0.84 ± 0.07 mb for the formation of 64Cu and 67Cu, respectively. These values are slightly lower than the respective values for a pure fission spectrum. The present results were compared with data calculated using the neutron spectral distribution and the recently critically analysed excitation function of each reaction given in the literature. The good agreement validates the reliability of those excitation functions. The feasibility of simultaneous production of 64Cu and 67Cu with fast neutrons is discussed.
TL;DR: An overview of the current status of radiopharmaceuticals in China for in vivo clinical use is provided and some important advances in the past three decades are described.
Abstract: Abstract The review provides an overview of the current status of radiopharmaceuticals in China for in vivo clinical use and also describes some important advances in the past three decades. Development of the diagnostic and therapeutic radiopharmaceuticals as well as basic research on radiopharmaceutical chemistry are being introduced. The radiotracers developed in China include: (1) Brain perfusion imaging agents and CNS radiotracers for β-amyloid plaques, σ1 receptors, and dopamine D2 or D4 receptors; (2) 99mTc- and 18F-labeled myocardial perfusion imaging agents; (3) tumor imaging agents including integrin-targeting radiotracer, novel sentinel lymph node imaging agents, hypoxia imaging agents, 99mTc-labeled glucose derivatives, σ2 receptor imaging agents, folate receptor imaging agents, and potential radiotracers for imaging of human telomerase reverse transcriptase expression; (4) Potential infection imaging agents; (5) Potential asialoglycoprotein receptor imaging agents; (6) Other imaging agents. Moreover, some prospects of research and development of radiopharmaceuticals in the near future are discussed.
TL;DR: In this paper, the effect of redox state and aqueous speciation on the uptake of neptunium by titanium dioxide (TiO2) and by calcium silicate hydrates (C-S-H) under alkaline conditions was investigated.
Abstract: Abstract Wet chemistry experiments were carried out to investigate the effect of the redox state and aqueous speciation on the uptake of neptunium by titanium dioxide (TiO2) and by calcium silicate hydrates (C-S-H) under alkaline conditions. TiO2 was chosen as a reference sorbent to determine the surface complexation behaviour of neptunium under alkaline conditions. C-S-H phases are important constituents of cement and concrete. They may contribute significantly to radionuclide retention due to their high recrystallization rates making incorporation the dominating sorption mechanism for many radionuclides (e.g. the actinides) on these materials. The sorption of neptunium on both solids was found to depend strongly on the degree of hydrolysis. On TiO2 Rd values for Np(IV), Np(V) and Np(VI) are identical at pH = 10 and decrease with progressing hydrolysis in case of Np(V) and Np(VI). On C-S-H phases, Rd values for the three redox states are also identical at pH = 10. While the Rd values for Np(VI) sorption on C-S-H phases decrease with progressing hydrolysis, the Rd values for Np(IV) and Np(V) sorption are not affected by the pH. In addition to the effect of hydrolysis, the presence of Ca is found to promote Np(V) and Np(VI) sorption on TiO2 whereas on C-S-H phases, the present wet chemistry data do not give unambiguous evidence. Thus, the aqueous speciation appears to have a similar influence on the sorption of the actinides on both types of solids despite the different sorption mechanism. The similar Rd values for Np(IV,V,VI) sorption at pH = 10 can be explained qualitatively by invoking inter-ligand electrostatic repulsion between OH groups in the coordination sphere of Np(V) and Np(VI). This mechanism was proposed earlier in the literature for the prediction of actinide complexation constants with inorganic ligands. A limiting coordination number for each Np redox state, resulting from the inter-ligand electrostatic repulsion, allows the weaker sorption of the highest hydrolysed Np(V,VI) species to be explained.
TL;DR: Biodistribution and imaging studies carried out in normal Wistar rats following intra-articular injection of 169Er-HA particulates in the knee joint showed near-complete retention of injected radioactivity within the synovial cavity with almost no activity leaching out to the other organs/tissue.
Abstract: Abstract Erbium-169 [T1/2 = 9.4 d, Eβ( max ) = 342 keV (45%) and 351 keV (55%), Eγ = 110.5 KeV (0.0014%)] is the most preferred radionuclide for radiation synovectomy (RSV) of digital joints. Radiolabeled particulates of appropriate size, wherein the radionuclide is irreversibly attached to the preformed particles, offer distinct advantages as the radiopharmaceuticals for use in RSV over other radiotherapeutic agents in terms of minimal leakage of radioactivity from the joint cavity. Hyroxyapatite (HA) particles, regarded as one of the most suitable carrier moiety for radiosynoviortheses applications, have been envisaged for labeling with 169Er with an aim to developing an agent for RSV of digital joints. Erbium-169 was produced with a specific activity of 415 ± 23 MBq/mg and radionuclidic purity of 99.22 ± 0.17% (both at the end of bombardment) by thermal neutron irradiation of enriched (98.2% in 168Er) erbium target at a flux of ∼ 8 · 1013 n/cm2 s for 21 d. HA particles (1–10 micrometer size), synthesized in-house, were labeled with 169Er in high yield and radiochemical purity (> 99%) using 5 mg of HA particulates at pH 7.5. The radiolabeled particulates showed excellent in vitro stability in normal saline and human serum. Biodistribution and imaging studies (using 171Er-HA) carried out in normal Wistar rats following intra-articular injection of 169Er-HA particulates in the knee joint showed near-complete retention of injected radioactivity within the synovial cavity with almost no activity leaching out to the other organs/tissue.
TL;DR: The FTIR study combined with biosorption experiments indicated that the thorium distribution and binding behavior on cell surface were associated with amino, hydroxyl groups and phosphate or sulphur functional groups, and might also be governed by electrostatic interaction.
Abstract: Abstract In order to understand the impact of microorganisms on the fate of thorium in soils, we investigated the thorium biosorption behavior and the corresponding mechanisms by the cells of Geotrichum sp. dwc-1, one of the dominant species of fungal group isolated from 3.5 m depth soil layer in Southwest China. It was observed that fast thorium adsorption onto cells of G. sp. dwc-1 could take place, with a high distribution coefficient Kd (0.93 mL/mg) obtained, when Geotrichum sp. dwc-1and thorium concentrations were 5 g/L and 10 mg/L, respectively. The thorium biosorption behavior was dependent on the pH value, and the lower pH could disrupt cell membrane of G. sp. dwc-1. At pH 1, thorium was accumulated in the cytoplasmic region of the cells. When pH was higher than 1, thorium was adsorbed on the cell surface of G. sp. dwc-1, like in periplasmic region or in the outer membrane. FTIR study combined with biosorption experiments further indicated that the thorium distribution and binding behavior on cell surface were associated with amino, hydroxyl groups and phosphate or sulphur functional groups, and might also be governed by electrostatic interaction. Moreover, PIXE and EPBS showed that ion-exchange mechanism contributed to the thorium biosorption process, in which the tetravalent thorium ions replaced smaller counter-ions (K+, Ca2+ and Fe3+) occuring on the cell surface.
TL;DR: In this article, metal carbonyl complexes were used for studying the gas-phase chemical behavior of Mo, Ru, W and Os isotopes with an on-line low temperature isothermal gas chromatography apparatus.
Abstract: Metal carbonyl complexes were used for studying the gas-phase chemical behavior of Mo, Ru, W and Os isotopes with an on-line low temperature isothermal gas chromatography apparatus. Short-lived Mo and Ru isotopes were produced by a Cf-252 spontaneous fission source. Short-lived nuclides of W and Os were produced using the heavy ion reactions F-19 + Tb-159 and Ho-165, respectively. Short-lived products were thermalized in a recoil chamber filled with a gas mixture of helium and carbon monoxide. The carbonyls formed were then transported through capillaries to an isothermal chromatography column for study of the adsorption behavior as a function of temperature. On-line isothermal chromatography (IC) experiments on Teflon (PTFE) and quartz surfaces showed that short-lived isotopes of the listed elements can form carbonyl complexes which are very volatile and interact most likely in physical sorption processes. Deduced adsorption enthalpies of Mo and Ru carbonyls were -38 +/- 2 kJ/mol and -36 +/- 2 kJ/mol, respectively. These values are in good agreement with literature data, partly obtained with different chromatographic techniques. A validation of the applied Monte Carlo model to deduce adsorption enthalpies with Mo isotopes of different half-lives proved the validity of the underlying adsorption model. The investigations using a gas-jet system coupled to a heavy ion accelerator without any preseparator clearly showed the limitations of the approach. The He and CO gas mixture, which was directly added into the chamber, will result in decomposition of CO gas and produce some aerosol particles. After the experiment of W-173 and Os-179 in the heavy ion experiments, the Teflon column was covered by a yellowish deposit; the adsorption enthalpy of W and Os carbonyls could therefore not be properly deduced using Monte Carlo simulations.
TL;DR: In this article, the activation stacked-foil thecnique on natural tungsten foils for deuteron energies up to 18.0 µmV was used to evaluate the performance of a target of a very thick target of enriched 186W by accelerated deuterons and compared with those obtained from the irradiation of the same target by accelerated protons.
Abstract: Abstract Excitation functions, thin- and thick-target yields for the 181−186gRe and 187W radionuclides were measured by the activation stacked-foil thecnique on natural tungsten foils for deuteron energies up to 18.0 MeV. These cross sections were validated by comparing the experimental results for thick-target yields with those calculated by integration of the thin-target yields. It was found that the maximum 186gRe content by irradiation of natural tungsten is about 55%, a higher value compared with the one found for proton beam, but not sufficient to use natural tungsten for medical purposes yet. Thus, in order to have a higher specific activity AS of 186gRe, the use of enriched 186W target is necessary. Therefore the irradiation of a thick target of enriched 186W by accelerated deuterons was studied and the results for the production of 186gRe were compared with those obtained from the irradiation of the same target by accelerated protons. It was found that the deuteron irradiation is preferable for three reasons: larger yield, less contamination by tantalum radioisotopes and smaller required amount of the target, which simplify the separation of the 186gRe from the target itself.
TL;DR: In this paper, radio ytterbium/samarium porphyrin complexes have been developed and stability of the complexes were checked in final formulation and human serum for 24 h, followed by partition coefficient determination and biodistribution studies in wild type and breast carcinoma-bearing mice.
Abstract: Radiolabeled porphyrins are potential tumor avid radiopharmaceuticals because of their behaviour in the human body, ability to complex various radionuclides, water solubility, low toxicity etc., in this work radio ytterbium/samarium porphyrin complexes have been developed. 175Yb and 153Sm labeled 5,10,15,20tetrakis(3,4-dimethoxyphenyl) porphyrins ([175Yb]TDMPP/[153Sm]-TDMPP) were prepared using 5,10,15,20tetrakis(3,4-dimethoxyphenyl) porphyrin (H 2 TDMPP) and [175Yb]YbCl 3 or [153Sm]SmCl 3 in 12–24 h at 60 ∘C. Stability of the complexes were checked in final formulation and human serum for 24 h, followed by partition coefficient determination and biodistribution studies in wild type and breast carcinoma-bearing mice. The radiocomplexes were obtained with acceptable radiochemical purity (> 95% (paper chromatography) and > 96% (HPLC) for [175Yb]-TDMPP and > 97% (paper chromatography) and >98% (HPLC) for [153Sm]-TDMPP) with specific activities of 12–15 GBq/mmol and 278GBq/mmol at the end of bombardment for [175Yb]-TDMPP and [153Sm]-TDMPP respectively. The partition coefficients were determined for [175Yb]-TDMPP and [153Sm]-TDMPP) (log P = 0.63 and log P = 0.96 respectively). The [175Yb]-TDMPP complex is mostly washed out from the circulation through kidneys. Liver and spleen also demonstrated significant activity uptake in 72 h post injection. Also [153Sm]-TDMPP, is mostly washed out from the circulation through kidneys, however lungs are the major accumulation sites. The [153Sm]-TDMPP complex demonstrated significant targeted uptake in breast carcinoma xenografts with tumor: blood ratios of 10.67, 10.47 and 19.01 in 24, 48 and 72 h respectively. Also interesting tumor: kidney/liver ratios were obtained. 153Sm-TDMPP properties suggest an efficient tumor targeting agent with high tumor-avidity. Further investigation on the therapeutic properties must be conducted.
TL;DR: In this article, the formation of nano-sized plutonium iron phosphate hydroxide structurally related to the rhabdophane group nanoparticles in 216-Z9 crib sediments from Hanford using transmission electron microscopy (TEM).
Abstract: The occurrence of plutonium dioxide (PuO2) either from direct deposition or from the precipitation of plutonium-bearing solutions in contaminated soils and sediments has been well described, particularly for the Hanford site in Washington State. However, past research has suggested that plutonium may exist in environmental samples at the Hanford site in chemical forms in addition to large size PuO2 particles and that these previously unidentified nano-sized particles maybe more reactive and thus more likely to influence the environmental mobility of Pu. Here we present evidence for the formation of nano-sized plutonium iron phosphate hydroxide structurally related to the rhabdophane group nanoparticles in 216-Z9 crib sediments from Hanford using transmission electron microscopy (TEM). The distribution and nature of these nanoparticles varied depending on the adjacent phases present. Fine electron probes were used to obtain electron diffraction and electron energy-loss spectra from specific phase regions of the 216-Z9 cribs specimens from fine-grained plutonium oxide and phosphate phases. Energy-loss spectra were used to evaluate the plutonium N4,5 (4d → 5f ) and iron L2,3 absorption edges. The iron plutonium phosphate formation may depend on the local micro-environment in the sediments, availability of phosphate, and hence the distribution of these minerals may control long-termmore » migration of Pu in the soil. This study also points to the utility of using electron beam methods for determining the identity of actinide phases and their association with other sediment phases.« less