Sorption Of Plutonium Research Articles

Influence of Na-Al phosphate glass leachates in clays sorption behavior toward radionuclides

The article presents the results of the study of the sorption of 90Sr, 137Cs, 233U, 237Np, 239Pu,and 241Am radionuclides from model groundwater, model leachate of aluminophosphate glass and Na2HPO4 solutions of different concentrations on bentonite clays of Kamalinskoye (Krasnoyarsk Territory), Desyaty Khutor (Republic of Khakassia), and Dinozavrovoye (Republic of Kazakhstan) deposits. We determined that the presence of aluminophosphate glass leachate in the liquid phase reduced the sorption activity of the studied clays towards caesium. The distribution coefficients of strontium depend more on the clay properties than on the liquid phase composition. However, with increasing concentration of phosphate ion, we observed an increase in the strength of sorbed strontium retention by clay. The sorption of uranium, neptunium, plutonium and americium, increased in the presence of components leached from the aluminophosphate glass-like matrix, and the strength of their fixation by clay increased.

Going deeper into plutonium sorption affected by redox

Sorption of Pu(VI) onto synthesized goethite under oxidizing and normal conditions was investigated, which revealed its pH dependence on different solid/liquid ratios. Pu speciation upon sorption on the solid phase was characterized via extended X-ray absorption fine structure (EXAFS) spectroscopy, while that in solution was assessed using ultraviolet–visible (UV–Vis) spectroscopy and liquid–liquid extraction. The obtained results demonstrate differences in plutonium behavior in the studied systems. Pu(VI) remains hexavalent on the goethite surface and in solution under oxidizing conditions. While Pu(IV) is stabilized on the mineral and Pu(V) is found in solution under normal conditions. This study provides the thermodynamic descriptions of these reactions.

Highly selective separation of plutonium using a mono-amide-based supported liquid membrane

ABSTRACT A monoamaide-functionalized supported liquid membrane was developed and employed for efficient and selective solid phase separation of Pu(IV). The membrane was prepared in a simple, one-pot process and was characterized for its homogeneity, stability and hydrophobicity. Various membrane parameters like sorption efficiency, sorption kinetics, sorption isotherm and equilibrium uptake capacity were studied for Pu(IV) in nitric acid medium. Langmuir and Freundlich isotherm models were employed for understanding the sorption mechanism of the membrane. Lagergren first-order kinetics and pseudo-second-order kinetics were applied to understand the plutonium sorption kinetics. The equilibrium sorption capacity of the membrane was found to be 27.18 mg g−1and the sorption kinetics followed a pseudo-second-order reaction with rate constants of 1.129 g mg−1 min−1 for Pu(IV). Stripping of Pu from the membrane was also studied to check the regeneration and reusability of the supported liquid membrane. The membrane was found to be very selective toward Pu(IV) in 4 M HNO3 medium, with separation factors 42 and 75 with respect to Am(III) and U(VI), respectively.

Correction to: Sorption of plutonium from aqueous medium containing oxalate using zero-valent iron nano particles

Correction to: Sorption of plutonium from aqueous medium containing oxalate using zero-valent iron nano particles

Sorption of plutonium from aqueous medium containing oxalate using zero-valent iron nano particles

Sorption of plutonium from aqueous medium containing oxalate using zero-valent iron nano particles

The self-assembled AgCd nanoclusters: A novel plutonium separating material

• Novel alloy clusters, i.e. Ag 32 Cd 12 (SR) 36 and Ag 32 Cd 12 (SR) 36 are prepared. • The Ag 32 Cd 12 clusters show high efficiency and selectivity for Pu seperation. • The oxygen-rich environments by self-assembly of Ag 32 Cd 12 is pivotal. The selective sorption of plutonium from radioactive wastes is of high economic and strategic importance. Herein, the self-assembled Ag 32 Cd 12 (SPh 4− OMe) 36 (SPh 4− OMe = 4-methoxyphenylthiolate) have been developed as a powerful plutonium separating material. Compared to its non-assembled analogue of the trimetallic Au 4 Ag 28 Cd 12 (SPh 4− OMe) 36 cluster, the bimetallic AgCd alloy cluster shows excellent binding affinity and selectivity to 239 Pu(IV) over the other radionuclides (such as 237 Np(V), 241 Am(III), etc). The maximum value of the distribution coefficient (Kd) and separation factors reaches 3 × 10 4 mL g −1 and 7.52 × 10 3 at pH = 3. The significantly higher selectivity of the AgCd clusters than that of the reported solid-phase materials might originate from the regular, inter-cluster assembly via formation of the cyclic …Ag-S…Ag-S… interactions in the exterior AgS 3 motifs.

Sequential injection analysis system with DGA resin for sample pretreatment in ICP-MS determination of 239Pu in nuclear industry samples

The monitoring of the presence of plutonium isotopes is a very important issue in both nuclear energy industry and environmental protection for human health risk assessment. The developed method for the determination of 239Pu isotope with ICP-QMS detection is based on the use of sequential injection analysis (SIA) system for the pretreatment of samples to be analyzed with the use of a commercial sorbent called diglycolamide (DGA-b) for the analyte preconcentration and separation from 238U, which is the source of the most significant isobaric interference 238U1H+. Optimizing the size of the sorbent bed and the conditions of analyte sorption and elution of plutonium and uranium provides the analytical procedure for 239Pu determination, where at total analysis time of 45 min (at flow rate 10 mL min−1) the evaluated method detection limit (MDL) for 100 mL sample volume was 88 mBq L−1. This is satisfactory detectability for applications in both technological and environmental samples.

Plutonium(IV) Sorption during Ferrihydrite Nanoparticle Formation.

Understanding interactions between iron (oxyhydr)oxide nanoparticles and plutonium is essential to underpin technology to treat radioactive effluents, in cleanup of land contaminated with radionuclides, and to ensure the safe disposal of radioactive wastes. These interactions include a range of adsorption, precipitation, and incorporation processes. Here, we explore the mechanisms of plutonium sequestration during ferrihydrite precipitation from an acidic solution. The initial 1 M HNO3 solution with Fe(III)(aq) and 242Pu(IV)(aq) underwent controlled hydrolysis via the addition of NaOH to pH 9. The majority of Fe(III)(aq) and Pu(IV)(aq) was removed from solution between pH 2 and 3 during ferrihydrite formation. Analysis of Pu–ferrihydrite by extended X-ray absorption fine structure (EXAFS) spectroscopy showed that Pu(IV) formed an inner-sphere tetradentate complex on the ferrihydrite surface, with minor amounts of PuO2 present. Best fits to the EXAFS data collected from Pu–ferrihydrite samples aged for 2 and 6 months showed no statistically significant change in the Pu(IV)–Fe oxyhydroxide surface complex despite the ferrihydrite undergoing extensive recrystallization to hematite. This suggests the Pu remains strongly sorbed to the iron (oxyhydr)oxide surface and could be retained over extended time periods.

Effect of Natural Organic Matter on Plutonium Sorption to Goethite.

The effect of citric acid (CA), desferrioxamine B (DFOB), fulvic acid (FA), and humic acid (HA) on plutonium (Pu) sorption to goethite was studied as a function of organic carbon concentration and pH using batch sorption experiments at 5 mgC·L-1 and 50 mgC·L-1 natural organic matter (NOM), 10-9-10-10 M 238Pu, and 0.1 g·L-1 goethite concentrations, at pH 3, 5, 7, and 9. Low sorption of ligands coupled with strong Pu complexation decreased Pu sorption at pH 5 and 7, relative to a ligand-free system. Conversely, CA, FA, and HA increased Pu sorption to goethite at pH 3, suggesting ternary complex formation or, in the case of humic acid, incorporation into HA aggregates. Mechanisms for ternary complex formation were characterized by Fourier transform infrared spectroscopy in the absence of Pu. CA and FA demonstrated clear surface interactions at pH 3, HA appeared unchanged suggesting HA aggregates had formed, and no DFOB interactions were observed. Plutonium sorption decreased in the presence of DFOB (relative to a ligand free system) at all pH values examined. Thus, DFOB does not appear to facilitate formation of ternary Pu-DFOB-goethite complexes. At pH 9, Pu sorption in the presence of all NOM increased relative to pH 5 and 7; speciation models attributed this to Pu(IV) hydrolysis competing with ligand complexation, increasing sorption. The results indicate that in simple Pu-NOM-goethite ternary batch systems, NOM will decrease Pu sorption to goethite at all but particularly low pH conditions.

Sorption and redox speciation of plutonium at the illite surface under highly saline conditions

Natural groundwater may contain high salt concentrations, such as those occurring at several potential deep geological nuclear waste repository sites. Actinide sorption to clays (e.g. illite) under saline conditions has, however, been rarely studied. Furthermore, both illite surface and ionic strength may affect redox speciation of actinides like plutonium. In the present study, Pu sorption to illite is investigated under anaerobic conditions for 3<pHm (=−log mH+)<10andmNaCl=1.0and3.2 molal (m). Results are compared with previous data for mNaCl=0.1m. According to redox potential measurements and based on Eu(III)-illite sorption data (taken as analogue of Pu(III)), the strong effect of mNaCl on overall Pu uptake observed for pHm<6 is mainly attributed to the presence of Pu(III) and its competition with Na+ for ion exchange sites. For pHm>6, overall Pu uptake is largely insensitive to mNaCl due to the prevalence of strongly adsorbed Pu(IV). By applying appropriate corrections to the activity coefficients of dissolved ions and using the 2-site protolysis non-electrostatic surface complexation and cation exchange (2 SPNE SC/CE) model, experimental data on Pu sorption to illite as a function of pH, Eh and mNaCl can be very well reproduced.

Sorption of plutonium to bacteria and fungi isolated from groundwater and clay samples

Preliminary studies of Pu(V) sorption to site-specific microorganisms isolated from the Triassic clay selected as an engineered barrier for the near surface low and intermediate level radioactive waste repository and from groundwater at the expected site were carried out. Adsorption of Pu(V) by bacteria attained the maxima values of 82–84 % at pH 6–7. The maximum adsorption values of Pu of about 100 % were found for Penicillium chrysogenum at pH 4.1. Bioreduction of Pu(V) to Pu(IV) by Bacillus cereus was observed, while any Pu(III) was not found in the system.

Investigation of 137Cs and plutonium isotope sorption–desorption in bio- and synthetic materials

Investigations on the pre-concentration of radionuclides (137Cs and plutonium isotopes) from fresh water on solid matrices are presented in this study. A particular focus was given to an innovative physico-chemical removal process such as adsorption of radionuclides from an aqueous medium on new type adsorbents, environmental-friendly materials. Sorption of the tested radionuclides from the lake water solution by environmental assays and synthetic sorbents was compared. Lake water was analyzed for main anions, micro- and macroelements, using ion and atomic absorption chromatography methods, respectively. Batch type and dynamic flow column laboratory experiments were performed. The sorption–desorption capacity of radionuclides by the tested sorbents was estimated based on the results of α- and γ-spectrometric measurements. According to the removal efficiency results, moss can be considered as the best sorbent for plutonium of the tested environmental-friendly sorbents, whereas the moss sorption capacity exceeded even that of the tested synthetic ones. The highest 137Cs removal efficiency from the lake water solution was obtained for granular activated carbon. Application of the dynamic flow method carried out in situ confirmed the reversibility of sorbed background 137Cs activity in the moss observed during the batch type experiments, and the method of the moss bed column turned to be unfit for the pre-concentration of 137Cs from the lake water. Application of a single moss bed column for the 137Cs and plutonium isotope pre-concentration for the first time carried out in situ allowed us to determine the activity concentration of 239,240Pu and 238Pu in the lake water – 4.87±0.98 and 0.67±0.21 mBq/m3, respectively. The reversible 137Cs and different plutonium sorption in the moss apparently indicates different binding properties of these radionuclides to the moss, therefore further investigations on this issue are foreseen.

Sorption and Redox Speciation of Plutonium at the Illite Surface.

The geochemical behavior of Pu strongly depends on its redox speciation. In this study, we investigated Pu sorption onto Na-illite, a relevant component of potential host rocks for high-level nuclear waste repositories, under anaerobic conditions. When contacting Pu (85% Pu(IV), 11% Pu(V), and 4% Pu(III); 8 × 10(-11) < [Pu]tot/M < 10(-8)) with illite in 0.1 M NaCl at pH between 3 and 10, Pu uptake was characterized by log Rd > 4 (Rd: distribution coefficient in L kg(-1)). Small amounts of aqueous Pu(V) were detected in solution on contact with illite after 1 week, which is not expected to be stable at the measured redox potentials (Eh) in our experiments. This observation suggests time-dependent reduction of Pu(V) to Pu(IV). After one year, log Rd values had increased compared to those after 1 week due to the reduction of weakly adsorbing Pu(V). For pH < 5, Pu(IV) and Pu(III) coexisted in solution under our experimental conditions, showing that Pu(IV) reduction to Pu(III) occurred in the illite suspension. Taking (i) surface complexation constants determined for Eu(III)-illite interaction (with redox-insensitive Eu(III) as a chemical analogue to Pu(III)), (ii) the known constant for Pu(III)-Pu(IV) redox transition, and (iii) measured Eh and pH, overall Pu uptake was well-predicted.

Sorption of plutonium on geological materials associated with a Chinese radioactive waste repository: influence of pH

The aim of this study is to characterize plutonium sorption particularly 239Pu distribution coefficients and the influence of pH on sorption processes in saturated geological materials used as a radioactive waste repository in China. The examined geological media is from a southwestern Chinese repository and consists of soil and slates. The backfill material consists of Na-bentonite from Inner Mongolia Gaomiaozi, and will be used at the Beishan high-level waste (HLW) repository, Gansu Province. The results show that the sorption capacity of Pu by geological medium in an acidic environment is low, but significantly increases with increasing pH.

Studies on BenzoDODA encapsulated polymeric beads for separation of plutonium from acidic solution

BenzoDODA encapsulated polymeric beads were synthesized by phase inversion technique and evaluated for the separation of plutonium from nitric acid medium. The beads were characterized by FT-IR, TGA and SEM techniques to gain insight into their structure and morphology. Kinetics studies showed that the sorption of plutonium was fast and, equilibrium was achieved within 60 min of equilibration. Sorption isotherm studies have indicated that uptake increases with the increase of metal ion concentration, the sorption data fitted well to Langmuir model. Back extraction was effectively carried out using 0.3 M Hydrazine + 0.5 M HNO3. Reusability of the beads was established by multiple sorption–desorption experiments. The beads were found to be quite stable as no significant structural deformation or leaching out of the extractant was observed in 4.0 M HNO3 solution, up to studied equilibration time of 8 days.

Modeling plutonium sorption to kaolinite: Accounting for redox equilibria and the stability of surface species

Plutonium with its particularly complex redox chemistry may be thermodynamically stable in the states +III to +VI depending on the redox conditions in the environment. Mineral surfaces can also affect Pu redox speciation. Therefore, the interpretation of Pu sorption data becomes particularly challenging, even for simplified laboratory experiments. The present study focuses on Pu sorption to kaolinite. Am(III), Th(IV), Np(V) and U(VI) literature sorption data are used as analogues for the corresponding Pu redox states to calibrate a simple surface complexation model, and the Nernst formalism is applied. Two independent pH–pe diagrams, one for the kaolinite surface and another for the aqueous phase, are constructed and superimposed. This allows visualization of the prevalent Pu redox state in both phases. The model suggests that the stability field of the most strongly adsorbing redox state is larger at the surface than in solution. Because Pu(V) weakly sorbs to kaolinite, it never prevails at the surface. Within the stability field of Pu(V) in 0.1M NaClO4 solution, Pu(VI) and Pu(IV) prevail at the kaolinite surface under oxidizing and slightly reducing conditions, respectively. By contrast, the Pu(IV)/Pu(III) boundary is hardly affected because both redox states strongly sorb to kaolinite, especially for pH>6. The present method is applied to literature data for Pu sorption to kaolinite. By estimating the pe from a Pu redox state analysis in solution, overall Pu uptake could be predicted. Generic equations are derived that are applicable to minerals and actinides other than kaolinite and Pu. The present study provides important progress in understanding Pu geochemistry, especially in the context of nuclear waste disposal where thermodynamic models are particularly necessary to predict Pu mobility.

Effect of fulvic acid surface coatings on plutonium sorption and desorption kinetics on goethite.

The rates and extent of plutonium (Pu) sorption and desorption onto mineral surfaces are important parameters for predicting Pu mobility in subsurface environments. The presence of natural organic matter, such as fulvic acid (FA), may influence these parameters. We investigated the effects of FA on Pu(IV) sorption/desorption onto goethite in two scenarios: when FA was (1) initially present in solution or (2) found as organic coatings on the mineral surface. A low pH was used to maximize FA coatings on goethite. Experiments were combined with kinetic modeling and speciation calculations to interpret variations in Pu sorption rates in the presence of FA. Our results indicate that FA can change the rates and extent of Pu sorption onto goethite at pH 4. Differences in the kinetics of Pu sorption were observed as a function of the concentration and initial form of FA. The fraction of desorbed Pu decreased in the presence of FA, indicating that organic matter can stabilize sorbed Pu on goethite. These results suggest that ternary Pu-FA-mineral complexes could enhance colloid-facilitated Pu transport. However, more representative natural conditions need to be investigated to quantify the relevance of these findings.

Plutonium sorption and desorption behavior on bentonite

Understanding plutonium (Pu) sorption to, and desorption from, mineral phases is key to understanding its subsurface transport. In this work we study Pu(IV) sorption to industrial grade FEBEX bentonite over the concentration range 10−7–10−16 M to determine if sorption at typical environmental concentrations (≤10−12 M) is the same as sorption at Pu concentrations used in most laboratory experiments (10−7–10−11 M). Pu(IV) sorption was broadly linear over the 10−7–10−16 M concentration range during the 120 d experimental period; however, it took up to 100 d to reach sorption equilibrium. At concentrations ≥10−8 M, sorption was likely affected by additional Pu(IV) precipitation/polymerization reactions. The extent of sorption was similar to that previously reported for Pu(IV) sorption to SWy-1 Na-montmorillonite over a narrower range of Pu concentrations (10−11–10−7 M). Sorption experiments with FEBEX bentonite and Pu(V) were also performed across a concentration range of 10−11–10−7 M and over a 10 month period which allowed us to estimate the slow apparent rates of Pu(V) reduction on a smectite-rich clay. Finally, a flow cell experiment with Pu(IV) loaded on FEBEX bentonite demonstrated continued desorption of Pu over a 12 day flow period. Comparison with a desorption experiment performed with SWy-1 montmorillonite showed a strong similarity and suggested the importance of montorillonite phases in controlling Pu sorption/desorption reactions on FEBEX bentonite.

Plutonium(IV) sorption to montmorillonite in the presence of organic matter

The effect of altering the order of addition in a ternary system of plutonium(IV), organic matter (fulvic acid, humic acid and desferrioxamine B), and montmorillonite was investigated. A decrease in Pu(IV) sorption to montmorillonite in the presence of fulvic and humic acid relative to the binary Pu-montmorillonite system, is attributed to strong organic aqueous complex formation with aqueous Pu(IV). No dependence on the order of addition was observed. In contrast, in the system where Pu(IV) was equilibrated with desferrioxamine B (DFOB) prior to addition of montmorillonite, an increase in Pu(IV) sorption was observed relative to the binary system. When DFOB was equilibrated with montmorillonite prior to addition of Pu(IV), Pu(IV) sorption was equivalent to the binary system. X-ray diffraction and transmission electron microscopy revealed that DFOB accumulated in the interlayer of montmorillonite. The order of DFOB addition plays an important role in the observed sorption/desorption behavior of Pu. The irreversible nature of DFOB accumulation in the montmorillonite interlayer leads to an apparent dependence of Pu sorption on the order of addition in the ternary system. This work demonstrates that the order of addition will be relevant in ternary systems in which at least one component exhibits irreversible sorption behavior.

Plutonium sorption and precipitation in the presence of goethite at 25 and 80 ○C

Abstract We have examined the sorption of aqueous Pu(IV) and intrinsic Pu colloids to goethite across a Pu concentration range that spans the solubility of Pu(IV) hydrous oxide, at 25 and 80 ℃, and after equilibration for over 100 days. The strong affinity of aqueous Pu(IV) for the goethite surface is explained by the epitaxial growth of bcc Pu4O7 nano-particles on goethite. The 3–5 nm Pu4O7 nano-particles are strictly associated with goethite, widely dispersed across the goethite surface, and stable over the timescale of months at both 25 and 80 ℃. There is no indication that the sorbed Pu4O7 nano-particles alter to PuO2 over time. Intrinsic Pu colloids were identified by TEM as 3–5 nm PuO2 nano-particles. They exhibit a weaker association with the goethite surface. Aggregation of PuO2 nano-particles was observed. There is no indication that the PuO2 nano-particles, once formed, will alter to Pu4O7 on goethite. Based on supernatant Pu concentrations, PuO2 nano-particle aggregation behavior is consistent with Pu(IV) hydrous oxide precipitation.