Uranium Radionuclides Research Articles

Uranium and Radium in Groundwater and Incidence of Colorectal Cancer in Georgia Counties, USA: An Ecologic Study.

Colorectal cancer (CRC) is the third most commonly occurring cancer in the United States, with higher incidence rates among Black populations. Groundwater concentrations of natural radionuclides uranium and radium have seldom been investigated in relation to CRC despite their known carcinogenicity. We investigate spatial patterns of CRC by race, and in relation to groundwater concentrations of uranium and radium, testing the hypothesis that uranium and radium in groundwater might differentially contribute to incident CRC in Black and White populations in counties of Georgia, USA. Black populations showed a higher incidence of CRC than White populations; the median incident rate difference was 9.23 cases per 100,000 (95% CI: 2.14, 19.40). Spatial cluster analysis showed high incidence clusters of CRC in similar regions for Black and White populations. Linear regression indicated there are, on average, 1-2 additional cases of colorectal cancer in counties with higher levels of radium in their groundwater, irrespective of race. Uranium was not associated with CRC. This ecologic study suggests that radium in groundwater may be linked with increased incidence of CRC, although it did not explain higher CRC incidence rates in Black populations. Further studies are needed to verify this association given the inherent limitations in the ecologic study design and the crude exposure assessment.

Modification of Ti3C2Tx nanostructure with KH2PO4 and chitosan for effective removal of strontium from nuclear waste.

Nanostructure titanium carbide MXene (Ti3C2Tx) was modified with KH2PO4 and chitosan to effectively remove strontium from nuclear wastewater. Nuclear waste includes radionuclides of uranium, thorium, strontium, and cesium, which are classified depending on the concentration of radionuclides. Nuclear waste with a high strontium concentration is the production waste of radiopharmaceutical production centers. Ti3C2Tx was synthesized from Ti3AlC2 using HF40% and HF in situ (MILD-Ti3C2Tx) in 24h at 313.15 and 333.15K. Morphology, structure, and functional groups were investigated using the XRD, SEM, EDS, FTIR, and BET analyses. The Sr(II)'s adsorption capacity on Ti3C2Tx-HF and Ti3C2Tx-HF in situ was obtained as 61.9 and 253.5mgg-1, respectively (temperature, 298.15K; pH, 7.00; contact time, 180min; and Sr(II) concentration, 150mgl-1). Ti3C2Tx-HF in situ showed fourfold adsorption due to more hydroxyl functional groups and larger interlayer spacing. Ti3C2Tx was modified with KH2PO4 and chitosan to investigate the mechanism of change of Sr(II)'s adsorption capacity, which increased to 370 and 284mgg-1, respectively. The structural results of modified Ti3C2Tx showed that the surface functional groups increased when modified with chitosan. In addition, modification with KH2PO4, through encapsulating large amounts of KH2PO4 between Ti3C2Tx layers, increased the possibility of Sr(II) diffusion between layers and electrochemical interactions with hydroxyl groups, and thus, increased its adsorption. Some experiments were designed to investigate the effect of parameters like initial concentration of Sr(II), contact time, temperature, and pH solution, as well as modified- and unmodified-Ti3C2Tx on adsorbent. The results revealed that the adsorption process of Sr(II) with pristine and modified-Ti3C2Tx follows pseudo-second-order kinetics and Freundlich heterogeneous isotherm model. Freundlich model isotherm indicates the presence of various functional groups on the surface and between the pristine and modified Ti3C2Tx layers. Electrostatic reactions and intra-sphere complexation were the two dominant mechanisms of the adsorption process.

A Mitochondria-Targeted Heptamethine Indocyanine Small Molecular Chelator for Attenuating Uranium Nephrotoxicity.

Radionuclide uranium has both a chemical and radioactive toxicity, leading to severe nephrotoxicity as it predominantly deposits itself in the kidneys after entering into human bodies. It crosses renal cell membranes, accumulates in mitochondria and causes mitochondrial oxidative damage and dysfunction. In this study, a mitochondria-targeted heptamethine indocyanine small molecule chelator modified with gallic acid (IR-82) is synthesized for uranium detoxication. Both gallic acid and sulfonic acid, as two hydrophilic endings, make IR-82, being excreted feasibly through kidneys. Gallic acid with polyphenol groups has a steady metal chelation effect and potent antioxidant ability, which may facilitate IR-82-alleviated uranium nephrotoxicity simultaneously by enhancing uranium decorporation from the kidneys and reducing mitochondrial oxidative damage. Cell viability assays demonstrate that IR-82 can significantly improve the cell viability of uranium-exposed human renal (HK-2) cells. It is also demonstrated to accumulate in mitochondria and reduce mitochondrial ROS and total intracellular ROS, as well as intracellular uranium content. In vivo imaging experiments in mice show that IR-82 could be excreted out through kidneys. ICP-MS tests further reveal that IR-82 can efficiently decrease the uranium deposition in mouse kidneys. IR-82 treatment improves the animal survival rate and renal function of experimental mice after high-dose uranium exposure. Collectively, our study may evidence that the development of uranium decorporation agents with kidney-mitochondrion dual targeting abilities is a promising strategy for attenuating uranium-induced nephrotoxicity.

σ-hole effect of halogen-bonded cocrystals causing tunable photoelectric properties for photocatalytic uranium removal

The mechanism of how the internal composition of halogen-bonded cocrystals affecting photoelectric properties is ambiguous. Herein, we report a series of stable halogen-bonded cocrystals containing I-, Br-based halogen bond donors and N-based halogen bond acceptor. The halogen bonds served an intrinsic hub, and the two parts (donor and acceptor) were spliced into a highly ordered periodic network with a tight electronic configuration. The charge transfer within lattice induced by the σ-hole effect activates disparate photoelectric phenomena. The results uncover that the degree of photoelectric response of cocrystals can be adjusted rationally by manipulating the intensity and density of σ-holes with an atomic precision at the molecular level. The experimental and theoretical studies of the σ-hole effect pave the way to simplify the design principle of functional cocrystals. Eventually, benefiting from the fascinating photoelectric activity, halogen-bonded cocrystals exhibited excellent photocatalytic reduction ability of radionuclide uranium.

Perilla frutescens: A new strategy for uranium decorporation

Radionuclide uranium is a great threat to human health, due to its high chemical toxicity and radioactivity. Finding suitable uranium decorporation to reduce damage caused by uranium internal contamination is an important aspect of nuclear emergency response. However, the poor selectivity and/or high toxicity of the only excretory promoter approved by Food and Drug Administration (FDA) is an obvious disadvantage. Herein, we choose an edible natural product, the traditional Chinese medicine called Perilla frutescens (PF), which has wide sources and can be used as an excellent and effective uranyl decorporation. In vivo uranium decorporation assays illustrate the removal efficiency of uranium in kidney were 68.87% and 43.26%, in femur were 56.66% and 54.53%, by the test of prophylactic and immediate administration, respectively. Cell level experiments confirmed that it had better biocompatibility than CaNa3-DTPA (CaNa3-diethylenetriamine pentaacetate, a commercial actinide excretion agent). In vitro static adsorption experiments exhibited that its excellent selectivity sorption for uranyl. All those results findings would provide new research insights about natural product for uranyl decorporation.

Amidoxime-functionalized hollow 2D-COFs for uranium separation

Constructing desirable morphology has been demonstrated to be an effective strategy for enhancing the capabilities of the covalent organic frameworks (COFs) for the processing of uranium. Traditional 3D-COFs only possess a limited number of structural nodes, not being the ideal structure for uranium adsorption, but 2D-COFs with rich structural nodes also suffer from reduced exposure of adsorption sites due to stacking during uranium treatment, which is not beneficial for achieving sustained and efficient adsorption. To this end, by polymerizing COFs on the silica carrier, followed by etching the silica carrier, and utilizing the conversion of nitrile to amidoxime groups as chelation sites, we designed and synthesized a hollow 3D-like structure of 2D-COFs (COF-TD-H-AO, similar to three-dimensional COFs) as adsorbents to capture the radionuclide uranium. Systematic studies were carried out for the adsorption characteristics of this material at different pH values and in the presence of interfering ions, as well as its adsorption thermodynamics and kinetics. Compared with COF-TD-AO (pure 2D-COFs) and SiO2@COF-TD-AO (unetched), COF-TD-H-AO exhibited a higher adsorption capacity as well as selective adsorption of uranium. This work provides an innovative perspective on material design and preparation by providing more adsorption sites in an effort to improve the capacity of adsorption and the selectivity of adsorption.

Environmentally friendly tea saponin foam detergents costabilized by GO-OH/SiO2 nanoparticles for removing radioactive surface contaminants

Currently, bare silica nanoparticles with low surface activity and weak stabilizing foam ability have restricted applicability in treating surface radioactive pollutants. To address potential issues with SiO2 as a foam stabilizer, a highly efficient foam stabilizer was fabricated by compounding silica with hydroxylated graphene oxide (GO-OH), which was prepared by hydrothermal modification of graphene oxide (GO). Then, an environmentally friendly foam detergent with high stability and high decontamination efficiency was developed using the natural surfactant tea saponin (TAS) as a foaming agent and a composite of silica and GO-OH (GO-OH/SiO2) as a foam stabilizer, which is named tea saponin foam detergent. For different types of surfactants, the structural and morphological characteristics of GO-OH, such as hydrophilic and surface oxygen groups, as well as the synergistic influence of GO-OH with SiO2 on foamability, foam stability, and detergency of the foam detergent, were studied. As a consequence, the TAS foam detergent has good stability with a drain half-life of 68 min. By hydrothermal modification of GO, the contact angle of water on GO-OH in air dropped to 63.2°, which was lower than that (73.0°) on GO. Furthermore, the hydrophilicity of GO-OH increased, and more oxygen-containing groups on GO-OH enhanced its absorption and enrichment of the radionuclide uranium and improved the decontamination rate of the TAS foam detergent. Moreover, when GO-OH was combined with SiO2, the dispersion and stability of SiO2 in the foam detergent improved, and the foam stability of the detergent subsequently further improved. Adding 2 wt% SiO2 and 0.1 wt% GO-OH to the detergent enhanced the foam drainage half-life of the detergent from 40 min to 68 min and improved the stability of the detergent by 70%. In addition, the synergistic action of GO-OH/SiO2 with TAS surfactant increased the liquid film thickness of the foam and the airflow resistance to support the weight-bearing capacity of the foam skeleton. As a result, it slowed the rate of foam disproportionation, reduced the bubble size, increased the bubble number, and finally improved the foam stability of the detergent. For simulated radioactive uranium pollutants on the surfaces of glass, stainless steel, and tiles, the foam detergent with the synergistic action of GO-OH/SiO2 and TAS surfactant had decontamination rates of 91.7%, 91.16% and 91.76%, respectively, which were 14.96%, 15.67% and 19.39% higher than that of TAS foam detergent without GO-OH/SiO2. The synergistic enhancement of GO-OH and SiO2 on foam stability and its adsorption and combination action with uranyl ions would be the main reasons to improve the detergency of the TAS foam detergent. Therefore, TAS foam detergent stabilized synergistically by GO-OH/SiO2 with high stability and efficient decontamination will be widely applied in nuclear emergencies and decommissioning decontamination of nuclear facilities.

Experimental Study on the Solidification of Uranium Tailings and Uranium Removal Based on MICP

The governance of uranium tailings aims to improve stability and reduce radionuclide uranium release. In order to achieve this goal, the uranium removal solution test and uranium tailings grouting test were successively carried out using microbially induced calcium carbonate precipitation (MICP) technology. The effect of MICP on the reinforcement of uranium tailings and the synchronous control of radionuclide uranium in the tailings were discussed. The solution test results show that Sporosarcina pasteurii could grow and reproduce rapidly in an acidic medium with an initial pH of 5. The uranium concentration decreased with the increase in MICP reaction time, and the removal efficiency reached 60.9% at 24 h. In the solidification test of tailings, the strength of tailings improved significantly after 12 days of reinforcement, with an increase in the cohesion of tailings by 2.937 times and an increased internal friction angle of 8.393°. The peak stress value of solidified tailings at the surrounding pressure of 50 kPa increased by 1.87 times, and the uranium concentration in the discharge fluid decreased by 76.91% compared to the blank group. This study provides valuable insights and references for safely disposing of uranium tailings.

Performance of Thermal-, Acid-, and Mechanochemical-Activated Montmorillonite for Environmental Protection from Radionuclides U(VI) and Sr(II)

Low-cost sorption materials based on the clay mineral of the smectite group—montmorillonite—were used for the removal of radionuclides uranium (VI) and strontium (II) from contaminated water. A wide range of industrial methods such as thermal treatment, acid activation, and mechanochemical activation were applied. Complex methods, such as SEM microscopy analysis, X-ray powder diffraction (XRD), thermal analysis, and nitrogen adsorption–desorption at −196 °C, were used to assess the characteristics of the structure of the obtained materials. The thermal treatment, acid activation, and mechanochemical activation resulted in changes in the surface properties of the clay minerals: specific surface area, porosity, and distribution of active sites. It was established that the mechanochemical activation of montmorillonite significantly increases the sorption characteristics of the material for U(VI) and Sr(II) and the acid activation of montmorillonite increases it for U(VI). The appropriateness of the experimental adsorption values for U(VI) and Sr(II) on modified montmorillonite to Langmuir and Freundlich models was found. Independently of the changes induced by acid attack, calcinations, or milling, the sorption of U(VI) and Sr(II) ions on treated montmorillonite occurs on a homogeneous surface through monolayer adsorption in a similar fashion to natural montmorillonite. Water purification technologies and modern environmental protection technologies may successfully use the obtained clay-based sorbents.

Radiometric and magnetic susceptibility characterization of soil profiles: Geophysical data and their relationship with Antarctic periglacial processes, pedogenesis, and lithology

Maritime Antarctica is still pedologically unexplored by proximal geophysical sensors. In-depth soil geophysical characterizations in depth can provide comprehensive information regarding how weathering, pedogenesis, and periglacial processes operate in periglacial environments, with advantages like non-invasive methodology, fast and precise data acquisition, practical equipment operation, and cost-effectiveness. This research aimed to carry out the first proximal gamma-spectrometric and magnetic geophysical characterization of soil profiles in maritime Antarctica and to relate the geophysical variables analyzed with periglacial processes, weathering, pedogenesis, geology, and landscape dynamics. The study was carried out in the Keller Peninsula (King George Island, Maritime Antarctica) with the pedological characterization of soil profiles, using two proximal geophysical sensors (gamma spectrometer and susceptibility meter) that quantify, respectively, soil radionuclides uranium, thorium and potassium as well as soil magnetic susceptibility. For that, twenty soil profiles were described and characterized, and soil samples were collected for physico-chemical analysis. In addition, readings were carried out with the two geophysical sensors in each soil profile, through soil horizons up to the lithic contact and/or permafrost top. We performed exploratory statistical analyses in R software as follows: visualizing the geophysical variables in soil depth for each profile and soil class, obtaining descriptive statistics among soil classes, analyzing geophysical variables by geology and soil classes, performing Spearman correlation between geophysical variables and soil physico-chemical attributes, and applying principal component analysis to pedological classes, geophysical variables, and soil physico-chemical attributes. The results showed that radionuclide contents increased with soil profile depth in all profiles and soil classes analyzed, except for Cryosols where permafrost is present, and cryoturbation was more pronounced. The potassium content was high in all soil profiles, evidencing the low degree of chemical weathering and leaching. The soil magnetic susceptibility values tended to decrease in depth, mainly where permafrost was present. The gravel content contributed more to the levels of radionuclide content. The clay content in some soil classes present contributed secondarily to uranium and thorium contents. Soil profiles located on marine terraces were influenced by periglacial reworking and deposition of different materials, showing increases in magnetic susceptibility values with soil depth by the absolute accumulation of ferrimagnetic minerals. Principal component analyses efficiently separated Regosols from other soil classes by soil κ related to lithology, whereas Cambisols and other soil classes were separated by radionuclide contents related to incipient pedogenesis. These findings may give new insights into understand this inhospitable continent.

Synthesis of propenone-linked covalent organic frameworks via Claisen-Schmidt reaction for photocatalytic removal of uranium

The type of reactions and the availability of monomers for the synthesis of sp2-c linked covalent organic frameworks (COFs) are considerably limited by the irreversibility of the C=C bond. Herein, inspired by the Claisen-Schmidt condensation reaction, two propenone-linked (C=C–C=O) COFs (named Py-DAB and PyN-DAB) are developed based on the base-catalyzed nucleophilic addition reaction of ketone-activated α-H with aromatic aldehydes. The introduction of propenone structure endows COFs with high crystallinity, excellent physicochemical stability, and intriguing optoelectronic properties. Benefitting from the rational design on the COFs skeleton, Py-DAB and PyN-DAB are applied to the extraction of radionuclide uranium. In particular, PyN-DAB shows excellent removal rates (>98%) in four uranium mine wastewater samples. We highlight that such a general strategy can provide a valuable avenue toward various functional porous crystalline materials.

Carbonate modified polyester nanofiltration membrane: Separation performance and mechanism investigation

The development of loose nanofiltration (LNF) membranes with high water flux and excellent separation performance is of great significance for wastewater treatment and resource recovery. As a green polyphenol with high molecular weight, tannic acid (TA) is an attractive aqueous monomer to prepare LNF membranes via interfacial polymerization (IP) with trimesoyl chloride (TMC). To the best of our knowledge, this work first reports a facile and delicate method to regulate reaction sites of the aqueous monomer by oxidizing a certain proportion of hydroxyl groups under weak alkaline condition caused by carbonate to tailor the morphology of polyester layer. The resulted nanobubbles generated by the reaction of carbonate with H+ produced during the IP reaction (which also promoted the IP process) rendered polyester layer nanovoids structure. Compared with the pristine membrane, the tailored morphology of active layer decreased 93.24% membrane resistance and significantly improved water flux up to 13.55 times, while maintained effective dye/salt separation. Furthermore, the polyester NF membrane possessed high electronegativity and abundant oxygen-containing functional groups, which could effectively remove heavy metal ions Pb2+, Cu2+ and radionuclide uranium (U(VI)) from water through Donnan effect and adsorption, with the rejection rates of above 95.39%, 94.71% and 99.35%, respectively. This work provides a noteworthy modification idea for the preparation of high-performance multifunctional LNF membranes derived from green polyphenols to deal with some challenges such as dye separation, heavy metal ions and radionuclide removal.

Thermodynamic Modeling of Thermal Processes Involving Radionuclides of Uranium, Plutonium, Europium on Heating of Nuclear Graphite in Air

Thermodynamic Modeling of Thermal Processes Involving Radionuclides of Uranium, Plutonium, Europium on Heating of Nuclear Graphite in Air

Biodistribution of naturally occurring radionuclides and radiocesium in wild European perch (Perca fluviatilis)

Wild European perch (Perca fluviatilis) is one of the most important freshwater fish species, in Sweden, due to its widespread and his value for recreational fishing. Little it is known regarding the biodistribution of naturally occurring radionuclides such as 238U, 234U, 226Ra, 210Po in perch. Therefore, in this study, perches from five lakes located in different counties in Sweden were collected to investigate the biodistribution of 238U, 234U, 226Ra, 210Po and 137Cs in organs and tissues of perch as well as their radiological impact. The results showed that uranium radionuclides ranged between 0.1 and 6 Bq/kg with an average value of 1.1 ± 1.5 Bq/kg. 226Ra varied from 0.4 to 8 Bq/kg with a mean concentration of 1.7 ± 1.9 Bq/kg. The ranged of 210Po was 0.5 – 250 Bq/kg, with an average value of 24 ± 52 Bq/kg. On the other hand, the highest activity concentration of 137Cs, 151 ± 1 Bq/kg, was detected in muscle samples of perch from Redsjösjön lake. For uranium radionuclides and 226Ra uptake from water is the main source whereas for 210Po and 137Cs the uptake is controlled by the perch diet. Regarding naturally occurring radionuclides, the perch tended to accumulated uranium radionuclides in fins, gills, and skin; 226Ra in bones, fins and skin and 210Po in the organs linked to digestive system. Finally, in case of consumption, it is advised the consumption of skinned fillets of perch due to the higher bioaccumulation of the radionuclides investigated in the skin and scales.

Study on the removal behavior of radionuclide uranium by nanoscale zero valent iron materials

Study on the removal behavior of radionuclide uranium by nanoscale zero valent iron materials

Facile Synthesis of MXene/MnO2 Nanocomposites for Efficient Removal of Radionuclide Uranium

The efficient removal of radionuclide uranium is crucial for sustainable nuclear energy and achieving a zero-carbon loop. In this study, we synthesized MXene/MnO2 nanocomposites and evaluated their ability to adsorb and reduce uranium. The results showed that the nanocomposites achieved a uranium removal rate of 99% and an adsorption capacity of 696 mg/g. Adsorption experiments were conducted under different conditions, including pH, cation, anion, and humic acid, and the uranium removal rate by the composite remained high at 91%, 70%, and 60% under the influence of pH = 4.97, 1.0 mM CaCl2, and 20 mg/L humic acid, respectively. The XRD and SEM analyses revealed that the uranium element was removed by the reduction and fixation of the composite material. These findings indicate that the MXene/MnO2 composite is an effective adsorption cleaning agent for the purification of radioactive nuclear wastewater, which has significant implications for pollution control.

State of Red Blood Indicators in Animals With Uranium Load

Research relevance: the study of uranium load on the state of red blood is relevant in connection with the effect on the bone marrow and changes in it. Research objectives: to study conditions of red blood indicators in animals with a uranium load. Research materials and methods: experiments were carried out on rabbits of the chinchilla breed, weighing 1.7-2 kg. The animals were divided into 4 groups depending on the altitude above sea level and on the receipt of uranium from food. To obtain posthemorrhagic anemia, a single bloodletting was performed in the amount of 3% of the animal’s weight. Research results: in animals that were in mid-mountain conditions, stimulation of the red and white sprouts of the bone marrow and a pronounced regenerative reaction to the preliminary administration of uranium radionuclide and blood loss were observed. Conclusions: in animals kept in mid-mountain conditions near the uranium tailing dump, the regenerative potential of red and white bone marrow sprouts was reduced, which was confirmed by the absence of regenerative, regenerative processes after blood loss.

Oxygen-containing functional groups enhance uranium adsorption by aged polystyrene microplastics: Experimental and theoretical perspectives

Although oxygen-containing functional groups generated during unavoidable aging play a key role in improving the adsorption performance of heavy metals by microplastics (MPs), little is known about the contribution of such groups to the interactions between highly toxic radioactive heavy metals and aged MPs. Here, we used a combination of batch experiments and density functional theory calculations to examine the effects and mechanisms of aging and the produced oxygen-containing functional groups, i.e., C═O, –OH, phenolic hydroxyl (–OHm), and –COOH, on the adsorption behavior of representative radionuclide uranium (U) on polystyrene (PS) MPs. The kinetic experimental results showed that the amount of U adsorption by the aged PS MPs was significantly higher than that of virgin PS MPs (P < 0.05). Binding-energy and thermodynamic data indicated that the affinity of PS MPs to a typical U species, i.e., uranyl, followed the order of PS═O–OHm > PS═O > PS–COOH > PS–OH > PS–OHm > virgin PS. Characterization and surface potential analyses demonstrated that the electronegative oxygen atoms in oxygen-containing functional groups in the aged PS MPs increased along with the aging time, and could serve as potential sites for electrostatic interactions with uranyl. Intramolecular interaction calculations confirmed that hydrogen bonding by oxygen-containing functional groups could strengthen the interactions between uranyl and aged PS MPs via electrostatic and polarization effects. Our findings provide an in-depth understanding of the role of aging in U adsorption by MPs, which is critical for assessing the fate of coexisting radionuclides and MPs in the environment, and their associated risks.

Allometric-kinetic model predictions of radionuclide dynamics across turtle taxa

Chelonians (turtles, tortoises, and sea turtles; hereafter, turtles) inhabit a wide variety of ecosystems that are currently, or have the potential in the future to become, radioactively contaminated. Because they are long-lived, turtles may uniquely accumulate significant amounts of the radionuclides, especially those with long half-lives and are less environmentally mobile. Further, turtle shells are covered by scutes made of keratin. For many turtle taxa, each year, keratin grows sequentially creating annual growth rings or layers. Theoretically, analysis of these scute layers for radionuclides could provide a history of the radioactivity levels in the environment, yet there are few previously published studies focused on the dynamics of radionuclide intake in turtles. Using established biochemical and ecological principles, we developed an allometric-kinetic model to establish relationships between the radionuclide concentrations in turtles and the environment they inhabit. Specifically, we calculated Concentration Ratios (CRs – ratio of radionuclide concentration in the turtle divided by the concentration in the soil, sediment, or water) for long-lived radionuclides of uranium and plutonium for freshwater turtles, tortoises, and sea turtles. These CRs allowed prediction of environmental concentrations based on measured concentrations within turtles or vice-versa. We validated model-calculated CR values through comparison with published CR values for representative organisms, and the uncertainty in each of the model parameters was propagated through the CR calculation using Monte Carlo techniques. Results show an accuracy within a factor of three for most CR comparisons though the difference for plutonium was larger with a CR ratio of about 200 times for sea turtles, driven largely by the uncertainty of the solubility of plutonium in sea water.

Constructing redox-active 3D covalent organic frameworks with high-affinity hexameric binding sites for enhanced uranium capture

The arduousness of nuclear waste disposal and the serious consequences of nuclear accidents motivate the development of efficient solid-phase extractants to provide enhanced protection. Herein, we report the first example of a hydroquinone-functionalized 3D covalent organic framework (DHBA-TAPM) with unique redox activity and high-affinity hexameric binding sites to be well suited as an efficient platform for selective capture and in situ reduction of radionuclide uranium. The high-affinity hexameric binding sites laced on the open 3D interconnected nanochannels showed high accessibility, and hollow tubular morphology enhanced the permeability, allowing greatly improved the utilization efficiency of the binding site. In addition, compared with adsorbents based on physical and/or chemical adsorption, the synergistic effect of the redox mineralization mechanism and high-affinity hexameric binding sites of DHBA-TAPM can significantly reduce the impact of binding site protonation under highly acidic conditions in chemisorption, thereby increasing the capture capacity. As a result, the DHBA-TAPM far outperform than other analogous adsorbents in terms of adsorption capacity and kinetics for uranium under highly acidic conditions. This work provides a facile strategy for the synthesis of functionalized 3D COFs and opens up the application of redox-active 3D COFs in environmental remediation.