Mg Of Uranium Research Articles

Layered charge separation in surface boron doped copper with phosphate groups boosts the electrochemical uranium extraction from seawater

Electrochemical uranium extraction from seawater is an attractive project for sustainable nuclear industry, whereas the active sites of electrode materials require further promotion on uranyl binding to increase the efficiency and kinetics of uranium extraction. Herein, we construct a strategy of layered charge separation in surface boron-doped copper with surface phosphate ions (B:Cu-PO4) for charge-enhanced uranyl binding and extraction in seawater. The B atoms were demonstrated to decrease the negative charge in surface Cu atoms and increase the negative charge in outer O atoms of PO43- groups, thus enhancing the uranyl binding. In a real seawater experiment, the B:Cu-PO4 extracted 24.9 μg of uranium from 10 L of seawater. Such performance corresponded to a considerable extraction capacity of 2.1 mg/g per day, which outperformed most of the state-of-the-art materials. The successful construction of charge separation in B:Cu-PO4 broadened the material design for uranium extraction from real seawater.

Facet-dependent electrochemical uranium extraction in seawater over Fe3O4 catalysts

Electrochemical uranium extraction from seawater represents an efficient strategy for the sustainable supplement of nuclear fuel, whereas the rational design of highly active electrocatalysts remains challenging due to the lack of study on structure–activity relationship. In this work, we demonstrated that the facet-dependent electrochemical uranium extraction from seawater by comparing Fe3O4 nanooctahedra with exposed {222} facet and Fe3O4 nanocubes with exposed {200} facet. In uranium-spiked electrolyte, the Fe3O4 nanooctahedra possessed extraction efficiency of 93.7 % in 8 h, which was 1.45-time larger than Fe3O4 nanocubes. In 10 L of real seawater, the Fe3O4 nanooctahedra extracted 17.49 μg of uranium within 8 h, corresponding to 3.49 mg/g of extraction capacity. The theoretical model revealed that {222} facet of Fe3O4 possessed a proper atomic distance to form a pocket of four O atoms and two Fe atoms. Such pocket enabled the binding of UO22+ with four O atoms, together with the low valent Fe atoms binding with the original two O atoms of UO22+. This binding model accounted for the more negative adsorption energy for UO22+ on {222} facet than that on {200} facet and the enhanced uranium extraction of Fe3O4 nanooctahedra.

A biomass fiber adsorbent grafted with phosphate/amidoxime for efficient extraction of uranium from seawater by synergistic effect

There are approximately 4 billion tons of uranium in the ocean, which is unmatched by the surface. Nevertheless, it's very challenging to extract uranium from the ocean due to the exceedingly low concentration of uranium in the ocean (about 3.3 μg L−1) as well as high salinity level. Current methods are often limited by selectivity, sustainability, economics, etc. Herein, phosphoric acid group and amidoxime group were grafted to skin collagen fibers through " initiated access” to design a new uranium extraction material, abbreviated as CGPA. Through laboratory simulation experiments, it is concluded that the maximum adsorption capacity of CGPA for uranium reaches 263.86 mg g−1. It has high adsorption, selectivity, and reusability for uranium. In the actual seawater extraction experiment, CGPA obtained 29.64 μg of uranium after extracting 10.0 L of seawater, and the extraction rate was 90.1%. The adsorbent has excellent effects in kinetics, selectivity, extraction capacity, renewability, etc. In the extraction of uranium from seawater, and is an economically feasible and industrially expandable adsorbent.

Gamma-ray spectroscopy for the characterization of uranium contamination in nuclear decommissioning

Decommissioning is the last step in the life cycle of a nuclear facility. After the evacuation of the facility components, the remaining structures such as concrete walls and floors must be surveyed to ensure that no residual contamination remains. It is a costly and time consuming activity, for which CEA develops fast alpha and beta detection methods allowing a full scanning of very large areas (hundreds of thousands of square meters) in legacy uranium enrichment plants. To support these developments, we present here complementary high-resolution gamma-ray spectroscopy analyses of a contaminated area at the gaseous diffusion uranium enrichment facility UDG, currently under decommissioning at Pierrelatte nuclear plant, France. Long measurements are performed with a High-Purity Germanium (HPGe) detector on the contaminated surface, and in a clean area to assess the natural gamma background of the concrete ground. The surface activity of uranium is 16.6 ± 6.0 Bq.cm-2, mainly due to 234U and 238U, most of the uncertainty coming from the non-uniform distribution of the contamination on the ground. This measurements also allowed us estimating the uranium enrichment of the contamination, which amounts to (0.80 ± 0.13) % of 235U mass fraction, consistently with the range of the Low Enrichment Plant where this measure was performed. Eventually, the background spectrum allowed us to determine the mass fractions of natural uranium, thorium and potassium in the concrete ground, which respectively amount to 3.8 ± 0.2. ppmU (i.e. 3.8 mg of uranium per kg of concrete), 7.4 ± 0.7 ppmTh, and (2.6 ± 0.1) %K of potassium.

Rapid and automated separation of uranium ore concentrates for trace element analysis by inductively coupled plasma – optical emission spectroscopy/triple quadrupole mass spectrometry

The present study documents an automated approach to performing elemental analysis on a large group uranium ore concentrate (UOC) samples. Here, 17 UOC samples, 2 quality control samples, and 26 process blanks were purified sequentially through a single 500 μL Uranium and TEtra Valent Actinides (UTEVA®) column. For each sample, the trace elemental impurities were separated from its dissolved uranium matrix on the UTEVA column and collected for analysis by inductively coupled plasma – optical emission spectroscopy / triple quadrupole mass spectrometry (ICP-OES/TQMS). The UTEVA column was subsequently regenerated prior to separation of the following sample. The column was efficiently regenerated, for each UOC, even after processing ~50 mg of uranium, cumulatively. The validity of the method was established by determining the trace impurities of two quality control uranium reference samples (CRM 124–1 and CUP-2). The current trace element measurements from the 17 UOC samples were compared to previously reported values from an interlaboratory comparison exercise, when available. The methodology employed here produces trace elemental analysis with excellent correlation to the previously reported data for many of the elements / samples, particularly when viewed through the context of existing geochemical comparisons tools (e.g. chondrite normalized variation plots).

Low doses of uranium and osteoclastic bone resorption: key reciprocal effects evidenced using new in vitro biomimetic models of bone matrix.

Uranium is widely spread in the environment due to its natural and anthropogenic occurrences, hence the importance of understanding its impact on human health. The skeleton is the main site of long-term accumulation of this actinide. However, interactions of this metal with biological processes involving the mineralized extracellular matrix and bone cells are still poorly understood. To get a better insight into these interactions, we developed new biomimetic bone matrices containing low doses of natural uranium (up to 0.85µg of uraniumper cm2). These models were characterized by spectroscopic and microscopic approaches before being used as a support for the culture and differentiation of pre-osteoclastic cells. In doing so, we demonstrate that uranium can exert opposite effects on osteoclast resorption depending on its concentration in the bone microenvironment. Our results also provide evidence for the first time that resorption contributes to the remobilization of bone matrix-bound uranium. In agreement with this, we identified, by HRTEM, uranium phosphate internalized in vesicles of resorbing osteoclasts. Thanks to the biomimetic matrices we developed, this study highlights the complex mutual effects between osteoclasts and uranium. This demonstrates the relevance of these 3D models to further study the cellular mechanisms at play in response to uranium storage in bone tissue, and thus better understand the impact of environmental exposure to uranium on human bone health.

Testing the effects of the presence of uranium in drinking water from individual wells in the village of Dubravica in the Branicevo district on public health

The village of Dubravica is partially located over the western lignite deposits of the Kostolac basin. The examination of the dry residue obtained from drinking water from two individual wells by X-ray diffraction analysis, based on a typical peak, showed the presence of uranium in drinking water. The indirect method by Rajkovic and associates showed that, in sample I, the concentration of uranium in drinking water was 85.5 percent higher (3.71 ?g/L) and that the concentration of uranium in sample II was only 22 percent lower (1.56 ?g/L) than the Maximum Allowable Concentration (MAC) values required by the Regulations (2 ?g/L). Analysis of the result of the introduction of uranium in the human body has shown that this way brings 0.84 to 2 mg of uranium in the human organism per annum or 0.09 to 0.22 mg of uranium is deposited annually in the kidney. Assessment of the potential health risk due to the presence of uranium in drinking water indicated that the population using drinking water from wells will be threatened by uranium in a short time interval. Regarding the long-term risk, the calculation has indicated that in the first sample of drinking water, about 25 inhabitants, and in the case of the second sample of drinking water, 10 inhabitants out of 1000 inhabitants are endangered. As the kidney is the organ in which uranium is deposited (accumulated) to the greatest extent, its presence causes weakening and failure of kidney function, which can destroy 75 percent of kidney function until the manifestation of the first clinical symptoms. This phenomenon is observed among the population along the rivers the Kolubara, the Drina, the Sava and the Morava and is called endemic nephropathy. The elements found in trace amounts (Pb, Cd, Si), live agents (bacteria and viruses), fungal plant toxins, genetic factors and immune mechanism can be listed as possible causes. However, uranium in drinking water has not been listed so far. The tests performed in this study clearly show the role of uranium in the epidemic, endemic nephropathy, which is growing and which is not at the acute phase of the disease but has already progressed to renal failure and end-stage kidney disease. Official data on the rise of endemic nephropathy and diabetes and increasing their share in diseases, as well as overall mortality rates, which amount to 18.19%, clearly indicate that the role of uranium in the Branicevo district environment should not be ignored. Since there are settlements on the terrain to be investigated, uranium and its migration through the environment must be monitored as all conditions for its migration are unfortunately favourable.

Actinide ion uptake from acidic radioactive feeds using an extraction chromatographic resin containing a branched dialkyl amide

A dialkyl amide with branched alkyl group, viz. N,N-di(2-ethylhexyl)-propionamide (D2EHPrA) was used as the organic extractant in an extraction chromatographic resin prepared for the first time and evaluated for the separation of uranium from acidic feeds. The distribution coefficient measurements, carried out at varying HNO3 concentrations, indicated an increase in the UO22+ ion sorption with increasing nitric acid concentration. The UO22+ ion sorption kinetics and sorption isotherms with this resin were investigated in details. The column studies indicated that 8.3 mg of uranium could be loaded on a 2.1 cm3 column bed volume containing 0.35 g resin. Batch distribution data for other actinides such as Np4+ and Pu4+ indicated that the resin can also be used for effective separation of these metal ions from acidic feeds. Though the resin showed effectiveness for Np and Pu, detailed investigations dealing with macro concentrations of metal ions (in gm quantities) were restricted to uranium only due to hazardous nature of plutonium and limited availability of neptunium. The encouraging results reported in this work is an indication of the possible application of this resin for the recovery or pre-concentration of UO22+, Np4+ and Pu4+ ions from large volumes of aqueous solutions of moderate acidity.

An automated micro-separation system for the chromatographic removal of uranium matrix for trace element analysis by ICP-OES

An automated, miniaturized, off-line separation technique is presented here using an Elemental Scientific Inc. microFAST MC system with UTEVA resin to extract the uranium matrix from its trace element impurities in aqueous media. The collected fractions were analyzed for ~ 30 trace elements using inductively coupled plasma – optical emission spectroscopy. Ten replicate samples were processed with a single column resulting in precision ranging from 3.3% to 6.2% relative standard deviation with regards to the trace element recoveries. Accuracy, with respect to trace element concentrations in the U3O8 Certified Reference Material 124-1, resulted in an average of 13.9% relative deviation while accuracy to the Canadian U3O8 reference material, CUP-2, resulted in an average relative deviation of 8.6%. The total separation time of this automated process was reduced to ~ 30 min per sample while employing a 0.5 mL UTEVA chromatographic resin bed and 2.5 mg of uranium.

Removal and recovery of uranium(VI) by waste digested activated sludge in fed-batch stirred tank reactor

This study demonstrated the removal and recovery of uranium(VI) in a fed-batch stirred tank reactor (STR) using waste digested activated sludge (WDAS). The batch adsorption experiments showed that WDAS can adsorb 200 (±9.0) mg of uranium(VI) per g of WDAS. The maximum adsorption of uranium(VI) was achieved even at an acidic initial pH of 2.7 which increased to a pH of 4.0 in the equilibrium state. Desorption of uranium(VI) from WDAS was successfully demonstrated from the release of more than 95% of uranium(VI) using both acidic (0.5 M HCl) and alkaline (1.0 M Na2CO3) eluents. Due to the fast kinetics of uranium(VI) adsorption onto WDAS, the fed-batch STR was successfully operated at a mixing time of 15 min. Twelve consecutive uranium(VI) adsorption steps with an average adsorption efficiency of 91.5% required only two desorption steps to elute more than 95% of uranium(VI) from WDAS. Uranium(VI) was shown to interact predominantly with the phosphoryl and carboxyl groups of the WDAS, as revealed by in situ infrared spectroscopy and time-resolved laser-induced fluorescence spectroscopy studies. This study provides a proof-of-concept of the use of fed-batch STR process based on WDAS for the removal and recovery of uranium(VI).

Successful Coupling of a Bis-Amidoxime Uranophile with a Hydrophilic Backbone for Selective Uranium Sequestration.

The amidoxime group (-RNH2NOH) has long been used to extract uranium from seawater on account of its high affinity toward uranium. The development of tunable sorbent materials for uranium sequestration remains a research priority as well as a significant challenge. Herein, we report the design, synthesis, and uranium sorption properties of bis-amidoxime-functionalized polymeric materials (BAP 1-3). Bifunctional amidoxime monomers were copolymerized with an acrylamide cross-linker to obtain bis-amidoxime incorporation as high as 2 mmol g-1 after five synthetic steps. The resulting sorbents were able to uptake nearly 600 mg of uranium per gram of polymer after 37 days of contact with a seawater simulant containing 8 ppm uranium. Moreover, the polymeric materials exhibited low vanadium uptake with a maximum capacity of 128 mg of vanadium per gram of polymer. This computationally predicted and experimentally realized selectivity of uranium over vanadium, nearly 5 to 1 w/w, is one of the highest reported to date and represents an advancement in the rational design of sorbent materials with high uptake capacity and selectivity.

Removal of U(VI) from Nuclear Waste Solutions by Bio-sorbents

Six bio-sorbents were used to remove uranium from simulated radioactive solutions UO2(NO3)2. Three types of peats, Polytrichium moss, Eichhórnia crássipes water plant and Cladonia stellaris lichen were used. About 2.7mg of uranium per 1g of sorbent was found in the peat samples after their interaction with UO2(NO3)2 solution (uranium initial concentration was 26mg/L, pH 4.4) during 24hours. Polytrichium moss, Cladonia stellaris lichen and Eichhórnia crássipes water plant were less effective: 2.3, 2.1 and 0.6mg of uranium per g of the sorbent respectively. The sorption on the peats is described by Freundlich isotherm. Numerous spherical compounds containing uranium 10 nanometers in diameter were found in the newly formed biotic sediments on the Polytrichium moss after the experiment.

Polyethyleneimine methylphosphonate: towards the design of a new class of macromolecular actinide chelating agents in the case of human exposition.

The use of uranium and to a minor extent plutonium as fuel for nuclear energy production or as components in military applications is under increasing public pressure. Uranium is weakly radioactive in its natural isotopy but its chemical toxicity, combined with its large scale industrial utilization, makes it a source of concern in terms of health impact for workers and possibly the general population. Plutonium is an artificial element that exhibits both chemical and radiological toxicities. So far, uranium (under its form uranyl, U(vi)) or plutonium (as Pu(iv)) decorporation or protecting strategies based on molecular design have been of limited efficiency to remove the actinide once incorporated after human exposure. In all cases, after human exposure, plutonium and uranium are retained in main target organs (liver, kidneys) as well as skeleton although they exhibit differences in their biodistribution. Polymers could represent an alternative strategy as their tropism for specific target organs has been reported. We recently reported on the complexation properties of methylcarboxylated polyethyleneimine (PEI-MC) with uranyl. In this report we extend our work to methylphosphonated polyethyleneimine (PEI-MP) and to the comparison between actinide oxidation states +IV (thorium) and +VI (uranyl). As a first step, thorium (Th(iv)) was used as a chemical surrogate of plutonium because of the difficulty in handling the latter in the laboratory. For both cations, U(vi) and Th(iv), the uptake curve of PEI-MP was recorded. The functionalized PEI-MP exhibits a maximum loading capacity comprised of between 0.56 and 0.80 mg of uranium (elemental) and 0.15-0.20 mg of thorium (elemental) per milligram of PEI-MP. Complexation sites of U(vi) and Th(iv) under model conditions close to physiological pH were then characterized with a combination of Fourier transform Infra Red (FT-IR) and Extended X-Ray Absorption Fine Structure (EXAFS). Although both cations exhibit different coordination modes, similar structural parameters with phosphonate functions were obtained. For example, the coordination sites are composed of fully monodentate phosphonate functions of the polymer chains. These physical chemical data represent a necessary basic chemistry approach before envisioning further biological evaluations of PEI-MP polymers towards U(vi) and Pu/Th(iv) contamination.

Maghemite nanoparticles bearing di(amidoxime) groups for the extraction of uranium from wastewaters

Polyamidoximes (pAMD) are known to have strong affinities for uranyl cations. Grafting pAMD onto the surface of functionalized maghemite nanoparticles (MNP) leads to a nanomaterial with high capacities in the extraction of uranium from wastewaters by magnetic sedimentation. A diamidoxime (dAMD) specifically synthesized for this purpose showed a strong affinity for uranyl: Ka = 105 M-1 as determined by Isothermal Titration Calorimetry (nano-ITC). The dAMD was grafted onto the surface of MNP and the obtained sorbent (MNP-dAMD) was characterized. The nanohybrids were afterward incubated with different concentrations of uranyl and the solid phase recovered by magnetic separation. This latter was characterized by zeta-potential measurements, X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Fluorescence spectroscopy (XRF), whereas the supernatant was analyzed by Inductively Coupled Plasma coupled to Mass Spectrometry (ICP-MS). All the data fitted the models of Langmuir, Freundlich and Temkin isotherms very well. These isotherms allowed us to evaluate the efficiency of the adsorption of uranium by MNP-dAMD. The saturation sorption capacity (qmax) was determined. It indicates that MNP-dAMD is able to extract up to 120 mg of uranium per gram of sorbent. Spherical aberration (Cs)-corrected High-Resolution Scanning Transmission Electron Microscopy (HRSTEM) confirmed these results and clearly showed that uranium is confined at the surface of the sorbent. Thus, MNP-dAMD presents a strong potential for the extraction of uranium from wastewaters.

Proteome changes in rat serum after a chronic ingestion of enriched uranium: Toward a biological signature of internal contamination and radiological effect.

The civilian and military use of uranium results in an increased risk of human exposure. The toxicity of uranium results from both its chemical and radiological properties that vary with isotopic composition. Validated biomarkers of health effects associated with exposure to uranium are neither sensitive nor specific to uranium radiotoxicity and/or radiological effect. This study aimed at investigating if serum proteins could be useful as biomarkers of both uranium exposure and radiological effect. Male Sprague-Dawley rats were chronically exposed through drinking water to low levels (40mg/L, corresponding to 1mg of uranium per animal per day) of either 4% (235)U-enriched uranium (EU) or 12% EU during 6 weeks. A proteomics approach based on two-dimensional electrophoresis (2D-DIGE) and mass spectrometry (MS) was used to establish protein expression profiles that could be relevant for discriminating between groups, and to identify some differentially expressed proteins following uranium ingestion. It demonstrated that the expressions of 174 protein spots over 1045 quantified spots were altered after uranium exposure (p<0.05). Using both inferential and non-supervised multivariate statistics, we show sets of spots features that lead to a clear discrimination between controls and EU exposed groups on the one hand (21 spots), and between 4% EU and 12% EU on the other hand (7 spots), showing that investigation of the serum proteome may possibly be of relevance to address both uranium contamination and radiological effect. Finally, using bioinformatics tools, pathway analyses of differentially expressed MS-identified proteins find that acute phase, inflammatory and immune responses as well as oxidative stress are likely involved in the response to contamination, suggesting a physiological perturbation, but that does not necessarily lead to a toxic effect.

Silica with immobilized phosphinic acid-derivative for uranium extraction

A novel adsorbent benzoimidazol-2-yl-phenylphosphinic acid/aminosilica adsorbent (BImPhP(O)(OH)/SiO2NH2) was prepared by carbonyldiimidazole-mediated coupling of aminosilica with 1-carboxymethylbenzoimidazol-2-yl-phenylphosphinic acid. It was obtained through direct phosphorylation of 1-cyanomethylbenzoimidazole by phenylphosphonic dichloride followed by basic hydrolysis of the nitrile. The obtained sorbent was well characterized by physicochemical methods, such as differential scanning calorimetry-mass spectrometry (DSC-MS), surface area and pore distribution analysis (ASAP), scanning electron microscopy (SEM), X-ray photoelectron (XPS) and Fourier transform infrared (FTIR) spectroscopies. The adsorption behavior of the sorbent and initial silica gel as well as aminosilica gel with respect to uranium(VI) from the aqueous media has been studied under varying operating conditions of pH, concentration of uranium(VI), contact time, and desorption in different media. The synthesized material was found to show an increase in adsorption activity with respect to uranyl ions in comparison with the initial compounds. In particular, the highest adsorption capacity for the obtained modified silica was found at the neutral pH, where one gram of the adsorbent can extract 176mg of uranium. Under the same conditions the aminosilica extracts 166mg/g, and the silica – 144mg/g of uranium. In the acidic medium, which is common for uranium nuclear wastes, the synthesized adsorbent extracts 27mg/g, the aminosilica – 16mg/g, and the silica – 14mg/g of uranium. It was found that 15% of uranium ions leached from the prepared material in acidic solutions, while 4% of uranium can be removed in a phosphate solution.

Design, Synthesis, and Characterization of a Bifunctional Chelator with Ultrahigh Capacity for Uranium Uptake from Seawater Simulant

Informed by density functional theory calculations, a novel bifunctional chelator, (Z)-2-[2-(N′-hydroxycarbamimidoyl)phenoxy]benzoic acid, was designed and synthesized for ultrahigh uranium uptake from seawater. Investigation of the ligand for uranium sorption was conducted in artificial seawater (pH = 8.2). An exceptional uranium uptake of 553 mg of uranium (g of sorbent)−1 was obtained with a theoretical saturation capacity of 710 mg g–1 obtained by fitting isotherm data with the Langmuir–Freundlich model. The resulting yellow precipitate was characterized via X-ray absorption fine structure (XAFS) at the U LIII-edge, with the extended XAFS spectra best fitted by a model where uranyl is coordinated by monodentate amidoxime, one chelating carboxylic acid, and two water molecules. These results are consistent with the formation of a uranium coordination polymer. The ultrahigh uranium uptake capacity obtained by the bifunctional chelating ligand makes it a promising candidate for deployment as a uranium ad...

US Transuranium and Uranium Registries case study on accidental exposure to uranium hexafluoride

The United States Transuranium and Uranium Registries’ (USTUR) whole-body donor (Case 1031) was exposed to an acute inhalation of uranium hexafluoride (UF6) produced from an explosion at a uranium processing plant 65 years prior to his death. The USTUR measurements of tissue samples collected at the autopsy indicated long-term retention of inhaled slightly enriched uranium material (0.85% 235U) in the deep lungs and thoracic lymph nodes. In the present study, the authors combined the tissue measurement results with historical bioassay data, and analysed them with International Commission on Radiological Protection (ICRP) respiratory tract models and the ICRP Publication 69 systemic model for uranium using maximum likelihood and Bayesian statistical methods. The purpose of the analysis was to estimate intakes and model parameter values that best describe the data, and evaluate their effect on dose assessment. The maximum likelihood analysis, which used the ICRP Publication 66 human respiratory tract model, resulted in a point estimate of 79 mg of uranium for the occupational intake composed of 86% soluble, type F material and 14% insoluble, type S material. For the Bayesian approach, the authors applied the Markov Chain Monte Carlo method, but this time used the revised human respiratory tract model, which is currently being used by ICRP to calculate new dose coefficients for workers. The Bayesian analysis estimated that the mean uranium intake was 160 mg, and calculated the case-specific lung dissolution parameters with their associated uncertainties. The parameters were consistent with the inhaled uranium material being predominantly soluble with a small but significant insoluble component. The 95% posterior range of the rapid dissolution fraction (the fraction of deposited material that is absorbed to blood rapidly) was 0.12 to 0.91 with a median of 0.37. The remaining fraction was absorbed slowly, with a 95% range of 0.000 22 d−1 to 0.000 36 d−1 and a median of 0.000 31 d−1. The effective dose per unit intake calculated using the dissolution parameters derived from the maximum likelihood and the Bayesian analyses was higher than the current ICRP dose coefficient for type F uranium by a factor of 2 or 7, respectively; the higher value of the latter was due to use of the revised respiratory tract model. The dissolution parameter values obtained here may be more appropriate to use for radiation protection purposes when individuals are exposed to a UF6 mixture that contains an insoluble uranium component.

Preparation of pure TiO2 sorption material

Determination of 236U/238U at natural ratios using accelerator mass spectrometry (AMS) requires overall purity of each step in the sample preparation procedures which are complex and include various chemicals. Therefore, the simplification of the procedures is desirable and can be done by implementing other effective separation materials. Among the prospective sorption materials, hydrated titanium dioxides showed promising properties for uranium extraction from various water samples. This paper shows the preparation of several titanium based sorption materials using an organic precursor and their characterization with several techniques in order to analyse crystal structure (XRPD, SEM, HRTEM, SAED) and residues of organic compounds (TG analysis and IR spectroscopy) and to quantify their sorption properties towards uranium. The practical sorption capacity of one of the prepared materials was as high as 260 mg of uranium per gram. AMS measurements showed that it is possible to prepare sufficiently pure titanium dioxides for the determination of 236U/238U ratio.

Comparison of uranium extraction from model fresh water on TiO–PAN and NaTiO–PAN composite absorbers

Possibility of uranium extraction on titanium oxide (TiO)–polyacrylonitrile (PAN) and sodium titanate (NaTiO)–PAN composite absorbers prepared from hydrated TiO and NaTiO embedded into a matrix of PAN binder was studied. Both TiO–PAN and NaTiO–PAN absorbers might be advantageous for repeated extraction of uranium from fresh water. Appropriate flow rates were found up to 60 BV h−1 for both the absorbers. Elution of uranium and regeneration of both the absorbers may be accomplished by hydrochloric acid solutions of concentration 0.1 mol L−1 and more. Practical sorption capacity (up to 10 % break-through) from tap water containing 2.3 μg U mL−1 was ~4.6 and ~1.5 mg of uranium per 1 mL of swollen TiO–PAN and NaTiO–PAN absorber, respectively.