bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of surface charge of an Fe-oxide and an organic matter dominated soil on iodide and pertechnetate sorption
Authors: Kaplan D. I. 
Published: December 2003

Summary
Iodine-129 and technecium-99 are commonly the largest contributors to the calculated health risk associated with long-term nuclear-waste burial. The high proportion of risk from these radionuclides is due to their large inventories in many types of waste, long half-lives, and the perception that they are highly mobile in sediments. In most aquifer systems, these radionuclides exist as anions, iodide (I-) and pertechnetate (TcO4
-), and sorb poorly to soils that possess a net negative charge. A series of iodide and pertechnetate sorption experiments were conducted over a pH range of 3 to 9. The two soils used in this study possessed a pH-dependent charge; one soil was collected from a wetland and derived most of its charge from organic matter, whereas the second soil was collected from an upland site and derived most of its charge from Fe/Al-oxide coatings. Although both soils had nearly identical particle size distributions, pH values, and mineral compositions, they had dissimilar surface charge and I- and TcO4
- sorption behavior. The pH where the wetland soil did not have any net charge (more specifically, the Point-of-Zero-Salt Effect) was 4.4. The pH where the upland soil did not have any net charge was 4.1. Under ambient conditions, the wetland soil had a pH of 4.2 and a slight positive net charge of +0.1meq/100g. The upland soil had a natural pH of 5.0 and a net charge of -0.25meq/100g. Both iodide and pertechnetate sorbed appreciably more to the wetland soil than to the upland soil, likely the result of more anion sorption sites derived from the organic matter in the wetland soil. In both soils, iodide sorption was greater and exhibited a greater pH-dependency than pertechnetate sorption. Pertechnetate exhibited anion exclusion (negative K
d values) or no sorption at pH values above the Point-of-Zero-Salt Effect. Iodide sorption decreased markedly as the pH increased to the zero-point-of-charge, and remained largely unchanged at pH values above the zero-point-of-charge.
Cross section measurements using gas and solid targets for production of the positron-emitting radionuclide O-14
Authors: Kovács Z. , Scholten B. , Tárkányi F. , Coenen H.H. , Qaim S.M. 
Published: December 2003

Abstract
Irradiation of nitrogen with protons leads to 11C (T
1/2=20.4min) via the well-known 14N(p,α) reaction. However, 14O (T
1/2=70.6s) and 13N (T
1/2=10min) are also formed as side products via the 14N(p,n) and 14N(p,d+pn) reactions, respectively. In this work detailed cross section measurements were carried out for those two side reactions up to 19.2MeV using N2 gas and nitrogen-containing solid targets. From the data, the thick-target yields and the exact level of radioactive impurities in 11C were calculated. In the case of 14O, the results also confirmed the possibility of producing this β
+ emitting radionuclide in sufficient quantities for PET investigations.
Redox speciation method for neptunium in a wide range of concentrations
Authors: Kirishima A. , Tochiyama O. , Tanaka K. , Niibori Y. , Mitsugashira T. 
Published: December 2003

SummaryThe adsorption method for determination of the distribution of neptunium among its oxidation states by the use of solvent impregnated resins and bismuth phosphate precipitates as adsorbents is described. For neptunium in concentration ranging from ∼10-10to ∼10-2.5M, Np(IV) and Np(VI) were quantitatively adsorbed on the impregnated resin in a solution of the acidity 1.0-0.1M HClO4, while Np(V) remained in the liquid phase. In the same condition, the precipitate of bismuth phosphate absorbed Np(IV) selectively, leaving Np(V) and Np(VI) in the liquid phase. By carrying out these adsorption methods in Ultrafree-MC Microporous Centrifugal Filter Units (Millipore Corporation), the oxidation state distribution of neptunium in acid solution can be determined in a simple manner with a small sample volume (500μl) regardless of its concentration.
Complete removal of uranyl nitrate from tissue matrix using supercritical fluid extraction
Authors: Kumar R. , Sivaraman N. , Senthil Vadivu E. , Srinivasan T. G. , Vasudeva Rao P. R. 
Published: December 2003

Summary
The removal of uranyl nitrate from tissue matrix has been studied with supercritical carbon dioxide modified with methanol alone as well as complexing reagents dissolved in methanol. A systematic study of various complexing agents led to the development of an extraction procedure for the quantitative recovery of uranium from tissue matrix with supercritical carbon dioxide modified with methanol containing small quantities of acetylacetone. The drying time and temperature employed in loading of uranyl nitrate onto tissue paper were found to influence the extraction efficiency significantly.
Solubility of thorium from Th3UO8 and ZrTh3UO10 ceramics
Authors: Curran G. , Rattray W. , Czerwinski K.R. 
Published: December 2003

Summary
The solubility of thorium from Th3UO8 and ZrTh3UO10 ceramics was studied to evaluate the solubility constants for the materials. Zirconium was added in order to investigate potential additional stabilization of the thorium matrix from ZrO2. Studies were performed from pH 4 to pH 9 under both 100 Argon and 10 CO2/90 Ar at 25°C in 0.1M NaClO4. Reaction kinetics and equilibrium concentrations were evaluated for each condition. Rate constants increased with pH and varied from 6×10-4 hr-1 to 4×10-2 hr-1. The surface area normalized dissolution rate decreased with increasing pH, the highest being 5×10-7gm-2 d-1 at pH 4. The solubility product constants calculated from the equilibrium concentrations for the two ceramics were equivalent, with K
{spTh₃UO₈}= -48.30.4 and K
{spZrTh₃UO₈= -47.90.9. The data was used to calculate the Th solution phase concentration. The result was compared to the dissolution of UO2 from pH 5-9 in 0.1M NaClO4 under a 1 CO2 atmosphere at 25°C. It was found that the U from the UO2 had a higher solution phase concentration than Th at high pH and was highly dependent upon the solution E
h of the evaluated conditions.
Multitracer studies on the permeation of rare earth elements through a supported liquid membrane containing 2-ethylhexyl phosphonic acid-2-ethylhexyl ester (EHEHPA)
Authors: Ambe Shizuko , Abe Daisuke , Ozaki Takuo , Ambe Fumitoshi 
Published: December 2003

Summary
The simultaneous permeation of Sc, Y, Ce, Pm, Eu, Gd, Yb and Lu through a 2-ethylhexyl phosphonic acid-2-ethylhexyl ester (EHEHPA)-decalin membrane supported on a microporous polytetrafluoroethylene sheet was studied using a multitracer. The permeation rates of the elements from feed solutions of various acidity into receiving solutions of 2mol dm-3 HCl were determined. The feed solution at pH 1.5 gave the highest percentage of permeation for Ce, Pm, Eu, Gd and Yb, amounting to about 90 after -25h permeation. The percentage of permeation of Y and Lu was the highest at pH 1, amounting to about 90 after -25h permeation. The permeation of Sc from all the feed solutions was less than 4 due to its adsorption on the vessel. The permeation from the feed solution at pH 1.5 into the receiving solutions of 1, 2, 3, 4 and 5mol dm-3 HCl showed that the maximum percentage of transport for Y and Yb was obtained in 2mol dm-3 HCl receiving solution and that for Lu in 2-4mol dm-3 HCl receiving solutions. The other elements gave a percentage of transport more than 90 in 1-5mol dm-3 HCl receiving solutions, showing no obvious HCl concentration effect. The permeability coefficients of these elements were determined. Solvent extraction of the elements by EHEHPA-decalin was also carried out for comparison.
Adsorption of barium on kaolinite, illite and montmorillonite at various ionic strengths
Authors: Atun G. , Bascetin E. 
Published: December 2003

SummaryThe sorption behaviour of Ba2+in three different clay minerals from various regions of Turkey has been investigated by means of a tracer technique using133Ba in batch experiments. Sorption of Ba2+on montmorillonite, kaolinite and illite has been studied in mixed solutions of BaCl2and NaCl at ionic strengths ranging from 1×10-3M to 1×10-1M. The L-shape exchange isotherms for Ba2+-Na+systems are well defined by a Langmuir type equation. The exchange capacity of Ba2+ions for all three clay minerals increased with decreasing ionic strength. The adsorption data were fitted to a Freundlich isotherm and empirical Freundlich parameters enabled to the generation of a site distribution function. The selectivity coefficients were nearly constant at low Ba loading and decreased as loading increased. This behavior was an indication of an ion exchange process between Ba2+and Na+ions.
Complexation of Ni(II) by α-isosaccharinic acid and gluconic acid from pH 7 to pH 13
Authors: Warwick Peter , Evans Nick , Hall Tony , Vines Sarah 
Published: December 2003

SummaryNickel reactions with gluconic acid (Gl) andα-isosaccharinic acid (ISA) have been investigated from pH 7 to pH 13.3. Measurement of the stoichiometries of the products of these reactions showed that NiGl and NiISA were formed at pH<7, Ni2Gl(OH)3and Ni2ISA(OH)3were formed at pH values between 7 and 10 and Ni2Gl(OH)4and Ni2ISA(OH)4were formed at pH>10. The stability constants for the formation of the soluble complexes were measured using an ion exchange resin method (Schubert method) at pH 7 and 13.3, and differential pulse polarography at pH 7. The polarographic measurements were performed in order to check the validity of the Schubert method at pH 7. This was due to the possibility of any cationic complexes that may have been formed sorbing to the resin. The importance of determining the stoichiometry of the reactions before calculating the stability constants from measurements taken using the Schubert method is emphasised.
The influence of ozone on ligand-assisted extraction of239Pu and241Am from Rocky Flats soil
Authors: Plaue J. W. , Czerwinski K.R. 
Published: December 2003

SummaryChemical extraction of239Pu and241Am from a Rocky Flats soil matrix was studied at 50°C using four ligands; citric acid and ascorbic acid at pH 2, EDTA and carbonate at pH 10. The soil was treated for a -12hour reaction period with ozone gas prior to the addition of ligands. With the carbonate ligand, the ozone treatment continued during the entire extraction. High Pu removal was found at pH 2 with ascorbic acid and pH 10 with carbonate. Both maintained redox conditions during the extraction. For the carbonate system, a trend of increased extraction with increasingEhand carbonate concentration was observed. Ozone treatment of soil prior to addition of EDTA at pH 10 and citric acid at pH 2 was shown to dramatically increase extraction of Am. Since no oxidation of Am occurred, the increased removal from ozone is mainly due to the oxidation of the soil phase containing the Am.
Uranium speciation in plants
Authors: Günther A. , Bernhard G. , Geipel G. , Reich T. , Roßberg A. , Nitsche H. 
Published: December 2003

Summary
Detailed knowledge of the nature of uranium complexes formed after the uptake by plants is an essential prerequisite to describe the migration behavior of uranium in the environment. This study focuses on the determination of uranium speciation after uptake of uranium by lupine plants. For the first time, time-resolved laser-induced fluorescence spectroscopy and X-ray absorption spectroscopy were used to determine the chemical speciation of uranium in plants. Differences were detected between the uranium speciation in the initial solution (hydroponic solution and pore water of soil) and inside the lupine plants. The oxidation state of uranium did not change and remained hexavalent after it was taken up by the lupine plants. The chemical speciation of uranium was identical in the roots, shoot axis, and leaves and was independent of the uranium speciation in the uptake solution. The results indicate that the uranium is predominantly bound as uranyl(VI) phosphate to the phosphoryl groups. Dandelions and lamb´s lettuce showed uranium speciation identical to lupine plants.
A fluorescence spectroscopic study on the speciation of Cm(III) and Eu(III) in the presence of organic chelates in highly basic solutions
Authors: Wang Zheming , Felmy Andrew R. , Xia Yuanxian , Mason M. J. 
Published: December 2003

SummaryThe speciation of Eu(III) and Cm(III) was investigated by time resolved laser fluorescence spectroscopy (TRLFS) over a range of base concentrations from 0.01M NaOH to 7.5M NaOH and in the presence of several organic chelates including EDTA, HEDTA, NTA, and oxalate. The results of this work suggest that both Eu(III) and Cm(III) form strong mixed ligand complexes with organic chelates and the hydroxyl groups(s) in dilute NaOH solutions. However, in concentrated NaOH solutions, Eu(III)-/Cm(III)-containing colloidal nanoparticles are the primary cause for the measured Eu(III)/Cm(III) in the aqueous solutions. Therefore, the interpretation of these data solely in terms of the formation of amphoteric hydroxyl species (e.g. Eu(OH)4-) would appear to be inappropriate. The organic chelating ligands form strong complexes with surface Cm(III)/Eu(III) sites of the colloidal nanoparticles. For Cm(III), such surface complexes show largely red-shifted fluorescence spectra as compared with the aqueous complexes and unusually short fluorescence lifetimes. The decreased fluorescence lifetimes are likely due to the presence of transition metal impurities in the nanoparticle and reduced inter-nuclear distance between neighboring Cm(III) centers.
Synthesis and characterization of neptunyl(VI) and plutonyl(VI) orthosilicates
Authors: Bessonov A.A. , Grigoriev M.S. , Ioussov A. B. , Budantseva N.A. , Fedosseev A.M. 
Published: December 2003

Summary
(NpO2)2SiO4·2H2O (I) and (PuO2)2SiO4·2H2O (II) have been prepared by hydrothermal synthesis technique. Chemical composition of (I) was attributed to the compound from its isostructurality with (UO2)2SiO4·2H2O; crystal unit cell parameters of (NpO2)2SiO4·2H2O have been refined as orthorhombic, a=8.365(5)Å, b=11.089(5)Å, c=18.640(9)Å with the space group Fddd. (PuO2)2SiO4·2H2O has not been found isostructural with uranyl(VI) and neptunyl(VI) analogues. Chemical composition of (II) was determined by chemical analysis and proved by the formula volume calculated from powder X-ray data. Indexing of X-ray powder pattern of the prepared compound gave the tetragonal unit cell with a=6.912(3), c=18.563(3)Å, possible space group I41/amd. Visible-near IR and IR absorption spectra of the prepared compounds have been measured in NaCl and KBr. f–f absorption band of PuO2
2+ in the visible spectrum of crystal (PuO2)2SiO4·2H2O is not splitted but its maximum is essentially shifted (up to 858nm) to the long wave region in comparison with hydrated PuO2
2+ ions. Visible-near IR absorption spectrum of crystal (NpO2)2SiO4·2H2O is close to that of aqueous neptunyl(VI) solution. Thermal behavior of synthesized compounds has been studied up to 800°C in air.
A comparision of the extraction of carrier-free176,177W and99Mo with that of U, Th, Am, Cm, La, Ce, Tm, Yb, Lu and Hf into Aliquat 336 in toluene from nitric, phosphoric, and sulphuric acid media
Authors: Johansson M , Alstad J. , Omtvedt J. P. , Skarnemark G. 
Published: December 2003

SummaryCarrier-free176,177W and99Mo have been extracted from 0.1-5.0M nitric, phosphoric and sulphuric acids into 0.22M Aliquat 336, CH3NR3Cl, in toluene. Their extraction properties have been compared to hafnium, to the lanthanides lanthanum, cerium, thulium, ytterbium and lutetium, and to the actinides americium, curium, thorium and uranium. From nitric acid solutions the extracted species of tungsten and molybdenum at low concentrations are probably CH3NR3· HMO4, where M=Mo or W. At higher nitric acid concentrations the extracted species are most likely similar to those of uranium,i.e. (CH3NR3)2·MO2(NO3)4and possibly CH3NR3·MO2(NO3)3. For the extraction from phosphoric acid solutions the major extracted complex is most likely CH3NR3·MO2(H2PO4)3, while the minor extracted complex may be (CH3NR3)2·MO2(H2PO4)4or even the more hydrolysed species CH3NR3·HMO4. From sulphuric acid solutions the extraction of molybdenum and tungsten has similarity with the extraction of uranium and thorium, although the decrease with acid concentration is slower.
Field study of the migration of90Sr in a weak loess aquifer
Authors: Liu C. L. , Li S. S. , Wang Z. M. , Yang Y. E. , Li B. , Jiang H. , Jiang L , Wang L. , Yao L. G. , Guo Z. M. , Li D. , Du Z. D. 
Published: December 2003

SummaryThe migration of90Sr in a weak loess aquifer was investigated in-situ in an Underground Research Facility. Quartz containing90Sr,3H and other nuclides was introduced into the aquifer with a stainless steel pipe. The local water flow field in the aquifer was monitored using a 3-dimensional sampling system. The contaminated area of the aquifer was marked out wholly with the help of a pre-installed stainless steel frame and cut into small pieces (samples) 3-dimensionally, and analyzed. The result of the -3year experiment indicated that90Sr had normal concentration distributions inYandZdirections. The migration rate of the mass center for90Sr inXdirection was calculated as 3.5×10-5cm/d, the distribution coefficient for90Sr in the aquifer was calculated as 7.4×102ml/g and the diffusion coefficient for90Sr in the aquifer inXdirection was calculated as 1.3×10-11m2/s.
Standardisation of the prompt gamma activation analysis method
Authors: Révay Zs. , Molnár G. L. 
Published: December 2003

Summary
A complete series of measurements was performed at the Budapest prompt gamma neutron activation analysis (PGAA) facility in order to determine the partial production cross sections of the most suitable neutron capture gamma rays for all naturally occurring elements, excluding noble gases. The values were determined directly, with internal standardisation using stoichiometric compounds and homogeneous mixtures (mainly water solutions) of known composition. A comparison with a recent measurement for 20 elements shows good agreement except for a few non-1/v cross sections. The new data are sufficiently accurate for quantitative multielement determinations in PGAA without the necessity of elemental standards.
Pu-Th separation studies employing di(2-ethylhexyl)isobutyramide (D2EHIBA) as extractant from nitric acid medium
Authors: Pathak P.N. , Prabhu D. R. , Rizvi G. H. , Ruikar P.B. , Kumbhare L.B. , Mohapatra P.K. , Manchanda V.K. 
Published: December 2003

Summary
An attempt has been made to explore the use of di(2-ethylhexyl)isobutyramide (D2EHIBA) as an extractant for the recovery of Pu from the (proposed) AHWR fuel fabrication scrap solution. The extraction of Pu in the hexavalent state has been found to be distinctly more efficient than that in the tetravalent state. Distribution studies have been carried out by maintaining Pu as Pu(VI) employing AgO as the oxidant. Scrubbing at 5M HNO3 has been proposed to reduce the interference due to the co-extracted Th(IV). Quantitative stripping of the extracted Pu was achieved using Hydroxyl Ammonium-Nitrate (HAN) as reductant. Ion exchange studies have been carried out for the final purification of Pu. It is proposed to employ the cation exchanger, Biorad AG 50X8 for the final purification of Pu from the stripped solution, keeping Pu as Pu(III).
New laser induced photoacoustic signal measurement method. Example of application: Identification of the uranium(IV)-dioxalato complex in solution
Authors: Mesmin Claire , Roudil Danièle , Hanssens Alain , Madic Charles 
Published: December 2003

SummaryA new laser induced photoacoustic signal measurement method was developed to optimise the parameters of photoacoustic detection: to obtain synchronous measurement, to avoid laser energy fluctuation, to get reproductibility and repeatability. The aim is to apply the technique to solution chemistry, and particularly to studies of the actinides. The initial validation of the new method was done using neodymium(III) and uranium(IV) solutions in acidic media. It was found that the sensitivity of detection of these ions by photoacoustic measurements is improved in comparison with absorption spectrophotometry. This advantage in radiochemistry is the possibility to study actinides at low concentration (<10-4M) to understand their behaviour in solution: speciation, precipitation, kinetics. An example is described and concerns the identification of the uranium(IV)-dioxalato complex in solution by proposing a new mechanism for the precipitation of U(C2O4)2·6H2O.In this work, a measurement device is proposed for rough pressure wave acquisition. It allows sensor definition, local phenomena observation and alternative LIPAS measurement.
Comparative study on the evaluation of gamma-dose rate above uranium mineralisation areas in Western Sudan
Authors: Sam A. K. , Sirelkhatim D. A. 
Published: December 2003

Summary
Absorbed dose rate received from natural external irradiation in uranium mineralisation areas at Jebel Uro, Jebel Kurun and Jebel Mun was evaluated from the measured activity concentrations of 238U, 232Th and 40K in rock samples. The analyses were performed using alpha-spectrometry and high-resolution gamma-ray spectrometry. A great spatial variability was observed in activity concentration of the primordial radionuclides indicating complexity in geological features. Converse to Jebel Mun, Uro and Kurun deposits exhibit very high U: Th mass ratio, the feature that characterized vein deposits. The resulting absorbed dose rate at 1m above bedrock level as estimated using dose rate conversion factors (DRCF) fall within the range of 70-500nGy/h (Mun), 600-6000nGy/h (Uro) and 80-300nGy/h (Kurun). At maximum, it corresponds to annual effective dose rate of 0.6mSv, 8mSv and 0.4mSv, respectively. Uranium is the principal producer of the surface radioactivity at Uro and Kurun as it contributes 99.6 and 95 of the total absorbed dose whereas, in Jebel Mun the cause of radioactive anomaly is due to 40K and 232Th. Regression analysis showed no correlation between uranium concentration and other radionuclides. Although, radioactive equilibrium is not likely to occur in surface and near-surface geological environments, however, daughter/parent activity concentration ratios along uranium series, viz. 234U:238U, Ra:U, 230Th:U, 210Po:U do not differ from unity in both Uro and Kurun deposits.
Efficacy of a new tan doped sol-gel sorbent for uptake of zinc
Authors: Khan Aslam , Ahmed Shujaat , Mahmood Farzana , Khokhar M. Younas , Riaz M. 
Published: December 2003

Summary
A TAN (1-(2-Thiazolylazo)-2-naphthol)) doped sol gel silica sorbent (reddish colour, porous, stable, hard, non- swelling) were prepared and investigated for the removal of Zn (II) from aqueous solutions. The kinetics, adsorption isotherm, equilibration time and pH effect on the removal were studied from non competitive aqueous solution to optimize the conditions to be utilized on a large scale. Fast equilibration was observed and adsorption equilibria were reached within 30minutes. Adsorption of zinc ions on the blank (un-doped) sol gel was found negligible. The maximum adsorption of Zn (II) ions onto the TAN doped sol-gel from single solutions were 2.33mg/g (0.035mmol/g). TAN doped sol gel can be regenerated through washing with a solution of 0.1M HCl solution. The maximum regeneration value was as high as 99.0. The TAN-doped sol gel silica is suitable at least for four adsorption-desorption cycles without experiencing considerable loss of adsorption capacity. The uptake route and the nature of the Zn-TAN complex have been discussed.