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Abstract: Uranium aerosol exposure can be a health risk factor for workers in the nuclear fuel industry. Good knowledge about aerosol dissolution and absorption characteristics in the gastrointestinal tract is imperative for solid dose assessments and risk management. In this study, an in vitro dissolution model of the GI tract was used to experimentally study solubility of size-fractionated aerosols. The aerosols were collected from four major workshops in a nuclear fuel fabrication plant where uranium compounds such as uranium hexafluoride (UF 6 ), uranium dioxide (UO 2 ), ammonium uranyl carbonate, AUC [UO 2 CO 3 ·2(NH 4 ) 2 CO 3 ] and triuranium octoxide (U 3 O 8 ) are present. The alimentary tract transfer factor, f A , was estimated for the aerosols sampled in the study. The transfer factor was derived from the dissolution in the small intestine in combination with data on absorption of soluble uranium. Results from the conversion workshop indicated a f A in line with what is recommended (0.004) by the ICRP for inhalation exposure to Type M materials. Obtained transfer factors, f A , for the powder preparation and pelletizing workshops where UO 2 and U 3 O 8 are handled are lower for inhalation and much lower for ingestion than those recommended by the ICRP for Type M/S materials f A = 0.00029 and 0.00016 vs. 0.0006 and 0.002, respectively. The results for ingestion and inhalation f A indicate that ICRP's conservative recommendation of f A for inhalation exposure is applicable to both ingestion and inhalation of insoluble material in this study. The dissolution- and subsequent absorption-dependence on particle size showed correlation only for one of the workshops (pelletizing). The absence of correlation at the other workshops may be an effect of multiple chemical compounds with different size distribution and/or the reported presence of agglomerated particles at higher cut points having more impact on the dissolution than particle size. The impact on dose coefficients [committed effective dose (CED) per Bq] of using experimental f A vs. using default f A recommended by the ICRP for the uranium compounds of interest for inhalation exposure was not significant for any of the workshops. However, a significant impact on CED for ingestion exposure was observed for all workshops when comparing with CED estimated for insoluble material using ICRP default f A . This indicates that the use of experimentally derived site-specific f A can improve dose assessments. It is essential to acquire site-specific estimates of the dissolution and absorption of uranium aerosols as this provides more realistic and accurate dose- and risk-estimates of worker exposure. In this study, the results indicate that ICRP's recommendations for ingestion of insoluble material might overestimate absorption and that the lower f A found for inhalation could be more realistic for both inhalation and ingestion of insoluble material., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Health Physics Society.)

Uranium oxide microparticles ingestion is one of the potential sources of internal radiation doses to the humans at accidental or undesirable releases of radioactive materials. It is important to predict the obtained dose and possible biological effect of these microparticles by studying uranium oxides transformations in case of their ingestion or inhalation. Using a combination of methods, a complex examination of structural changes of uranium oxides in the range from UO 2 to U 4 O 9 , U 3 O 8 and UO 3 as well as before and after exposure of uranium oxides in simulated biological fluids: gastro-intestinal and lung-was carried out. Oxides were thoroughly characterized by Raman and XAFS spectroscopy. It was determined that the duration of expose has more influence on all oxides transformations. The greatest changes occurred in U 4 O 9 , that transformed into U 4 O 9-y. UO 2.05 and U 3 O 8 structures became more ordered and UO 3 did not undergo significant transformation., (© 2023. The Author(s).)

As a biosorbent, algae are frequently used for the biotreatment or bioremediation of water contaminated by heavy metal or radionuclides. However, it is unclear that whether or not the biomineralization of these metal or radionuclides can be induced by algae in the process of bioremediation and what the mechanism is. In this work, Ankistrodsemus sp. has been used to treat the uranium-contaminated water, and more than 98% of uranium in the solution can be removed by the alga, when the initial uranium concentration ranges from 10 to 80 mg/L. Especially, an unusual phenomenon of algae-induced uranium biomineralization has been found in the process of uranium bioremediation and its mineralization mechanism has been explored by multiple approaches. It is worth noticing that the biomineralization of uranium induced by Ankistrodsemus sp. is significantly affected by contact time and pH. Uranium is captured rapidly on the cell surface via complexation with the carboxylate radical, amino and amide groups of the microalgae cells, which provides nucleation sites for the precipitation of insoluble minerals. Uranium stimulates Ankistrodsemus sp. to metabolize potassium ions (K + ), which may endow algae with the ability to biomineralize uranium into the rose-like compreignacite (K 2 [(UO 2 ) 6 O 4 (OH) 6 ]•8H 2 O). As the time increased, the amorphous gradually converted into compreignacite crystals and a large number of crystals would expand over both inside and outside the cells. To the best of our knowledge, this is the first investigated microalgae with a time-dependent uranium biomineralization ability and superior tolerance to uranium. This work validates that Ankistrodsemus sp. is a promising alga for the treatment of uranium-contaminated wastewater., (Copyright © 2022. Published by Elsevier B.V.)

Direct isotope ratio analysis of solid uranium particulates on cotton swipes was achieved using a solution-based microextraction technique, coupled to a quadrupole inductively coupled plasma - mass spectrometer (ICP-MS). This microextraction-ICP-MS methodology provides rapid isotopic analysis which could be applicable to nuclear safeguards measurements. Particulates of uranyl nitrate hexahydrate (UO 2 (NO 3 ) 2 ·6H 2 O) and uranyl fluoride (UO 2 F 2 ) ranging from 6 μm to 40 μm in length were transferred to cotton swipes with a particle manipulator. The microextraction probe then delivers a 5% nitric acid (HNO 3 ) solvent onto the swipe surface to extract the uranium species. The extracted sample is then delivered to the ICP-MS for isotopic determination. The majority of uranium signal (∼99% and ∼94% for UO 2 (NO 3 ) 2 ·6H 2 O and UO 2 F 2 , respectively) was detected in the first 15 s extraction, while subsequent extractions on the same location had low or no U signal, suggesting near complete removal of the solid uranium compounds from the swipe surface. Ten samples (for each of the uranium compounds), were analyzed for their isotopic composition. For UO 2 (NO 3 ) 2 ·6H 2 O, the determined isotope ratios resulted in a % relative difference (% RD) from the referenced isotope ratios of 0.97, 1.0, and 7.3% for 234 U/ 238 U, 235 U/ 238 U, and 236 U/ 238 U, respectively. The % RD of the UO 2 F 2 isotope ratios were 1.9 and 0.60% for 234 U/ 238 U and 235 U/ 238 U, respectively. The preliminary limits of detection were determined to be 0.002, 0.4, and 60 pg for 234 U, 235 U and 238 U, respectively This work demonstrates that microextraction ICP-MS is a rapid and sensitive method that could directly determine uranium isotope ratios of UO 2 (NO 3 ) 2 ·6H 2 O and UO 2 F 2 particulates on cotton swipes., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The preparation of synthetic (Zr,U)SiO4 solid solution is challenging, as the conventional high-temperature solid-state method limits the solubility of uranium (4 ± 1 mol%) in the orthosilicate phase due to its thermodynamic instability. However, these compounds are of great interest as a result of (Zr,U)SiO4 solid solutions, with uranium contents exceeding this concentration, being observed as corium phases formed during nuclear accidents. It has been identified that hydrothermal synthesis pathways can be used for the formation of the metastable phase, such as USiO4. The investigation carried out in this study has indeed led to the confirmation of metastable (Zr,U)SiO4 compounds with high uranium contents being formed. It was found that (Zr,U)SiO4 forms a close-to-ideal solid solution with uranium loading of up to 60 mol% by means of hydrothermal treatment for 7 days at 250 °C, at pH = 3 and starting from an equimolar reactant concentration equal to 0.2 mol L−1. A purification procedure was developed to obtain pure silicate compounds. After purification, these compounds were found to be stable up to 1000 °C under an inert atmosphere (argon). The characterisation methods used to explore the synthesis and thermal stability included powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and Raman spectroscopies, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). [ABSTRACT FROM AUTHOR]

Leaching of uranium, thorium and rare earth from the monazite selective solution residue were studied by conventional leaching--two-stage countercurrent leaching was studied. The effects of various factors on the leaching was investigated. The results show that the leaching rates of uranium, thorium and rare earth are 98.66 %, 95.37 % and 64.23%, respectively under suitable conditions using conventional leaching method. Using the two-stage countercurrent leaching method, the leaching rates of uranium, thorium and rare earth can be increased by 0.5%~1.0%, the residual acid of the leaching solution can be reduced by more than 50%, and the solid-liquid separation performance of the slurry can be improved to a certain extent. [ABSTRACT FROM AUTHOR]

Polynuclear metal hydride clusters play important roles in various catalytic processes, with most of the reported polynuclear metal hydride clusters adopting a polyhedral three‐dimensional structure. Herein, we report the first example of a planar tetranuclear uranium hydride cluster [(CpCMe2CMe2Cp)U]4(μ2‐H)4(μ3‐H)4 (U4H8). It was synthesized by reacting an ansa‐bis(cyclopentadienyl) ligand‐supported uranium chloride precursor [(CpCMe2CMe2Cp)U]3(μ2‐Cl)3(μ3‐Cl)2 with NaHBEt3. The presence of hydrides in U4H8 was confirmed by NMR spectroscopy and its reactivity with phenol and carbon tetrachloride. DFT calculations also facilitated the determination of the hydrides' positions in U4H8, featuring four bridging μ2‐H ligands and four face‐capping μ3‐H ligands, with the four U centers arranged in a rhombic geometry. The U4H8 represents not only the first example of planar polynuclear actinide metal hydride cluster but also the uranium hydride cluster with the highest nuclearity reported to date. [ABSTRACT FROM AUTHOR]

This paper describes the nuclear-forensic characterization of materials provided by the Nuclear Forensic International Technical Working Group within the 7th Collaborative Material Exercise. The characterized materials were two powdered uranium material samples labelled ES-1 and ES-3 and two uranium metal samples labelled ES-2 and ES-4. A combination of several analytical techniques was used by a group of Czech laboratories to the identification of chemical compounds and the determination of the uranium isotopic and elemental composition of all four samples. Those results allowed for an unambiguous conclusion that ES-1 was depleted uranium trioxide, ES-2 was depleted uranium-vanadium alloy, ES-3 was depleted uranium nitrate, and ES-4 was depleted uranium metal. A further conclusion was that ES-2 cannot originate from the same source as the other three samples and that ES-1, ES-3, and ES-4 had a common source material. The highlights of this work were in obtaining the isotopic composition of uranium, including minor isotopes, in the early (24-hour) phase of the exercise using the Secondary Ion Mass Spectrometry in a single-particle measurement mode and in the application of the Neutron Activation Analysis with uranium separation prior to irradiation for the elemental screening of the uranium samples. [ABSTRACT FROM AUTHOR]

Porphyrinoid metal-organic frameworks (MOFs) with dual effective uranium uptake sites were synthesized through combined in-situ and post-synthetic method. The MOF10@5 demonstrates the uptake amount of uranium reaches 1476 mg/g under visible-light irradiation. The PN-MOF10@5 with dual uranyl uptake sites yields the amount of extracting uranyl of 1590 mg/g under visible-light irradiation. The density functional theory (DFT) calculations reveal strong interaction between uranyl and dual uranyl effective active sites. These MOFs demonstrate a powerful synthesis strategy for uranium extraction materials with dual effective active sites. [ABSTRACT FROM AUTHOR]

Reactions of uranium tri‐ and tetrahalides, UBr3, UI3, UCl4, and UI4, with different cyanides MCN (M=K, Ag) in liquid anhydrous ammonia led to three novel uranium(IV) cyanide compounds. The reaction of UCl4 in the presence of KCN resulted in the compound [U(CN)(NH3)8]Cl3 ⋅ 3NH3, while UBr3 and UI3 were oxidized in the presence of AgCN to form the compounds ∞1[ ${{}_{\infty }{}^{1}[}$ (μ‐CN){(H3N)5U(μ‐NH2)3U(NH3)5}]Br4 ⋅ 2NH3, and ∞1[ ${{}_{\infty }{}^{1}[}$ (μ‐CN){(H3N)5U(μ‐NH2)3U(NH3)5}]I4 ⋅ 2NH3. The reaction of UI4 with KCN in aNH3 also yielded the compound ∞1[ ${{}_{\infty }{}^{1}[}$ (μ‐CN){(H3N)5U(μ‐NH2)3U(NH3)5}]I4 ⋅ 2NH3. The compounds ∞1[ ${{}_{\infty }{}^{1}[}$ (μ‐CN){(H3N)5U(μ‐NH2)3U(NH3)5}]X4 ⋅ 2NH3 (X=Br, I) crystallize in different space groups, Pmn21 (no. 31) and Imm2 (no. 44), respectively. In both cases, the ∞1[ ${{}_{\infty }{}^{1}[}$ (μ‐CN){(H3N)5U(μ‐NH2)3U(NH3)5}]4+ cation forms infinite strands. We conducted quantum‐chemical calculations and Intrinsic Bond Orbital analyses on the observed [U(CN)(NH3)8]3+ cation and the [(μ‐CN)2{(H3N)5U(μ‐NH2)3U(NH3)5}]3+ model cation to gain insight into the bonding situation. [ABSTRACT FROM AUTHOR]

The speciation of uranium bis(trifluoromethylsulfonyl)imide (TFSI) species formed from UI3(THF)4 in butyl-methylpiperidinium bis(trifluoromethylsulfonyl)imide ([BMPip][TFSI]) and [BMPip][TFSI]/HTFSI was investigated by X-ray absorption fine structure (XAFS) spectroscopy. Following the dissolution of UI3(THF)4 in the room temperature ionic liquid (RTIL), X-ray absorption near edge spectroscopy (XANES) indicates that U(III) did fully oxidize to U(VI) in [BMPip][TFSI] while a U(VI)/U(IV) mixture was obtained in [BMPip][TFSI]/HTFSI media. Extended X-ray absorption fine structure (EXAFS) results are consistent with the formation of UO2(TFSI)2(THF)3 in [BMPip][TFSI]. The U-S(TFSI) distance (i.e., 3.81(4) Å) is consistent with the presence of TFSI ligands coordinated to the UO22+ unit in monodentate mode. In [BMPip][TFSI])/HTFSI, EXAFS indicates the presence of UO2(TFSI)2(THF)3 (~ 35%) and of a U(IV) species coordinated to THF and TFSI ligands. The number of TFSI ligands coordinated to U(IV) (i.e., ~ 0.5) is consistent with the presence of an outer-sphere U(IV)-TFSI complex. [ABSTRACT FROM AUTHOR]

We describe a study of the influence of cryptand denticity on the structural, electronic, and electrochemical properties of UIII-containing cryptates. Two cryptands (2.2.2 and 2.2.1) are reported. The cryptand with the smaller denticity leads to negative electrochemical potentials and shorter bond lengths that are consistent with a better fit for UIII than the larger cryptand. These studies provide insight into the rational design of cryptand-based ligands for trivalent uranium. [ABSTRACT FROM AUTHOR]

UCl4, UBr4, UBr5, or UO2Cl2 reacted with excess liquid ammonia – in adventitious presence of moisture and/or air – and formed some peculiar uranium compounds of which we present the crystal structures. [(NH3)7(N3)U(μ‐O)U(NH3)8]Cl5 ⋅ 7NH3 contains a dinuclear μ‐O‐bridged uranium(IV) cation, [{(NH3)4UO2}2(μ‐O)]Cl2 ⋅ 4NH3 features a dinuclear μ‐O‐bridged uranyl(VI) cation, while the compounds [(U(VI)O2)2(U(V)O2)2(μ3‐O)2(NH3)12]Br2 ⋅ 6NH3 and [(U(VI)O2)4(U(V)O2)4(μ3‐O)4(NH3)22]Br4 ⋅ 16NH3 are mixed‐valent containing uranyl(V)‐uranyl(VI) units. For these tetra‐ and octanuclear complex cations we observed that the O atoms of the uranyl(V) units can be μ2‐ and even μ3‐bridging to uranyl(VI) units, while the O atoms of the latter are acting as terminal ligands only. [(NH3)8U(μ‐N)U(NH3)5(μ‐N)UO2(NH3)4]Br6 ⋅ 18NH3 presents the first example of a compound where the isoelectronic species UO22+ and UN2 formed a complex with the NUN unit bridging to the U atom of the uranyl(VI) cation. As it is can be difficult to distinguish between N and O atoms with X‐ray diffraction, quantum‐chemical calculations at the DFT‐PBE0/TZVP level of theory were carried out which unequivocally confirmed the atom assignments in the crystal structures. The chemical bonding in the complex cations was studied using intrinsic bonding orbitals and allowed for an additional discrimination of the U(V) and U(VI) atoms in the mixed‐valent compounds. [ABSTRACT FROM AUTHOR]

The evolution of the uranium chemical state in uranium compounds, principally in the oxides, is of concern in the context of nuclear fuel degradation under storage and repository conditions, and in accident scenarios. The U–O system shows complicated phase relations between single‐valence uranium dioxide (UO2) and different mixed‐valence compounds (e.g. U4O9, U3O7 and U3O8). To try resolving the electronic structure associated with unique atomic positions, a combined application of diffraction and spectroscopic techniques, such as diffraction anomalous fine structure (DAFS), can be considered. Reported here is the application of two newly developed routines for assessing a DAFS data set, with the aim of refining the uranium X‐ray dispersion corrections. High‐resolution anomalous diffraction data were acquired from polycrystalline powder samples of UO2 (containing tetravalent uranium) and potassium uranate (KUO3, containing pentavalent uranium) using synchrotron radiation in the vicinity of the U L3 edge (17.17 keV). Both routines are based on an iterative refinement of the dispersion corrections, but they differ in either using the intensity of a selection of reflections or doing a full‐pattern (Rietveld method) refinement. The uranium dispersion corrections obtained using either method are in excellent agreement with each other, and they show in great detail the chemical shifts and differences in fine structure expected for tetravalent and pentavalent uranium. This approach may open new possibilities for the assessment of other, more complicated, materials such as mixed‐valence compounds. Additionally, the DAFS methodology can offer a significant resource optimization because each data set contains both structural (diffraction) and chemical (spectroscopy) information, which can avoid the requirement to use multiple experimental stations at synchrotron sources. [ABSTRACT FROM AUTHOR]

The features of uranium mining on Kazakhstan's enterprises have been examined, and uranium deposits located in the Syrdarya and Shu-Sarysu depressions have been described. Actual and projected data on the development of technological blocks in areas with complex geological structures have been analyzed and compared. Core samples were collected and, using X-ray diffraction analysis, quantitative and qualitative characteristics as well as mineral compositions of ores from various productive horizons of uranium deposits in the Syrdarya and Shu-Sarysu depressions were comparatively analyzed. It was determined that the ores in the Syrdarya depression are relatively homogeneous compared to those in the Shu-Sarysu depression, although in some places, clay minerals and gypsum are present, which hinder the uranium leaching processes. In the ores of the Shu-Sarysu depression, clay minerals that impede the uranium leaching processes are present in certain areas. Microscopic analysis of core material samples using a LEICA DM 2500 P microscope revealed particle sizes and shapes, as well as their distribution within the structure of host rocks in the productive horizon. Using X-ray diffraction analysis, mineral compositions of sediment-forming components during uranium well mining in the considered productive horizons were determined and comparatively analyzed. It was established that in the geotechnological wells of the Syrdarya depression, sediments of predominantly chemical origin, such as gypsum, are formed. However, in the geotechnological wells of the Shu-Sarysu depression, sediments of mechanical origin, consisting predominantly of quartz particles and clay minerals, are formed. Based on the obtained data, a method for intensifying underground uranium leaching in complex geological conditions has been developed, which involves dissolving sediment formations and increasing the oxidative–reductive potential of the leaching solution. The proposed and experimentally substantiated universal methodology for enhancing uranium well production involves the dissolution and prevention of precipitation using hydrofluoric acid solutions, as well as the oxidation of uranium dioxide with hydrogen peroxide. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterisation of thorium(IV), uranium(III), and uranium(IV) complexes supported by a sterically demanding triamidoamine ligand with N‐diphenyl‐tert‐butyl‐silyl substituents. Treatment of ThCl4(THF)3.5 or UCl4 with [Li3(TrenDPBS)] (TrenDPBS={N(CH2CH2NSiPh2But)3}3−) afforded [An(TrenDPBS)Cl] (An=Th, 1Th; U, 1U). Complexes 1An react with benzyl potassium to afford the cyclometallates (TrenDPBScyclomet) [An{N(CH2CH2NSiPh2But)2(CH2CH2NSiPhButC6H4)}] (An=Th, 2Th; U, 2U). Treatment of 1An with sodium azide affords [An(TrenDPBS)N3] (An=Th, 3Th; U, 3U). Reaction of 3Th with potassium graphite affords 2Th. In contrast, 3Th reacts with cesium graphite to afford the doubly‐cyclometallated (TrenDPBSd‐cyclomet) ate complex [Th{N(CH2CH2NSiPh2But)(CH2CH2NSiPhButC6H4)}2Cs(THF)3] (4). In contrast to 3Th, reaction of 3U with potassium graphite produces the uranium(III) complex [U(TrenDPBS)] (5), and 5 can also be prepared by reaction of potassium graphite with 1U. The loss of azide instead of conversion to nitrides contrasts to prior work when the silyl group is iso‐propyl silyl, underscoring how ligand substituents profoundly drive the reaction chemistry. Several complexes exhibit T‐shaped meta‐C−H⋅⋅⋅phenyl and staggered parallel π–π‐stacking interactions, demonstrating subtle weak interactions that drive ancillary ligand geometries. Compounds 1An–3An, 4, and 5 have been variously characterised by single crystal X‐ray diffraction, multi‐nuclear NMR spectroscopy, infrared spectroscopy, UV/Vis/NIR spectroscopy, and elemental analyses. [ABSTRACT FROM AUTHOR]

The monomeric and dimeric uranium azide complexes {[(CH3)2NCH2CH2NPiPr2]2U(N3)2} (2) and {[(CH3)2NCH2CH2NPiPr2]2U(N3)2}2 (3) were synthesized by treating complex 1 with NaN3 at 60 and −20 °C, respectively. A temperature-induced single-crystal to single-crystal transformation of 3 to 2 was observed. The reduction of either 2 or 3 with KC8 yields a uranium nitride complex {[(CH3)2NCH2CH2NPiPr2]4U2(μ-N)2} (4). [ABSTRACT FROM AUTHOR]

The toxic and the hazardous ramifications that affect both the environment and human beings due to the existence of uranium in wastewater are a huge challenge towards a sustainable environment. Uranium removal from wastewater is a big difficulty that is becoming more severe as the world's population grows and energy demand rises. A hydrothermal and freeze-drying process is used to create a chitosan/graphene oxide/poly (vinyl alcohol) aerogel (CH/GO/PVA) for a very effective and selective uranium removal. Batch experiments were used to examine hexavalent uranium (VI) sorption from wastewater. The efficiency of U (VI) removal was investigated for time of contact, various pH, dosage of sorbent, initial concentration of U (VI), and temperature values. Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Energy Dispersive Spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller are utilized to describe the composition, morphology, polymer formation and nanocomposites. Kinetic and Freundlich equations, and the pseudo-second-order are used to illustrate the adsorption process. The adsorption capacity of U (VI) reaches its maximum of 1247 mg g–1 when an initial uranium concentration is 380 mg L–1, and the highest uranium removal efficiency is 98.44%. Thermodynamic study reveals an endothermic and spontaneous adsorption mechanism. Furthermore, the as-synthesized GO/CS/PVA aerogel has good mechanical as well as thermal stability, and can be utilized six times before losing a substantial portion of its original removing effectiveness. [ABSTRACT FROM AUTHOR]

A series of bidentate, viz., 1,1'-(1,2-ethylene)-3,3'-dimethyldiimidazoline-2,2'-diylidene (L1), 1-methyl-3-(2-pyridylmethyl)-imidazoline-2-ylidene (L2) and tridentate, viz., 1,3-bis(2-pyridyl)-imidazoline-2-ylidene (L3) ligands have been obtained from their corresponding imidazolium salts through deprotonation reactions. Treatment of UO2Cl2(THF)3 with one equivalent L3 produces air-stable U(VI)-carbene complex 3, characterized by elemental analysis, FTIR, NMR spectroscopy as well as extended X-ray absorption fine structure (EXAFS) analysis. EXAFS result indicates that the ligand is bonded through one C and two N-atoms to the uranium atom. Attempts to synthesize uranyl complexes derived from L1 and L2 were also successful but these complexes are decomposed quickly within one hour at room temperature. 3 produces pure UO2 powder when heated under an argon atmosphere from room temperature to 600 °C with constant heating rate of 5 °C/min. The solid-state UV–Vis spectrum of the compound shows absorption peaks at 332 and 450 nm. The excitation spectrum of 3 (at λem = 520 nm) exhibits two almost symmetrical peaks at 273 and 368 nm. Density functional theory-based quantum mechanical calculations indicate that a partial covalent interaction exists between the carbene C and U while a weak non-covalent interaction exists between carbene N and U atoms. [ABSTRACT FROM AUTHOR]

This study synthesized (3-aminopropyl)triethoxysilane-functionalized porous silica (AP@MPS) to adsorb aqueous uranium (U(VI)). To comprehensively analyze the surface properties of the AP@MPS materials, a combination of SEM, BET, XPS, NMR, and zeta potential tests were conducted. The adsorption experiments for U(VI) revealed the rapid and efficient adsorption capacity of AP@MPS, with the solution condition of a constant solution pH = 6.5, an initial U(VI) concentration of 600 mg × L−1, a maximum U(VI) capacity of AP@MPS reaching 381.44 mg-U per gram of adsorbent, and a removal rate = 63.6%. Among the four types of AP@MPS with different average pore sizes tested, the one with an average pore size of 2.7 nm exhibited the highest U(VI) capacity, particularly at a pH of 6.5. The adsorption data exhibited a strong fit with the Langmuir model, and the calculated adsorption energy aligned closely with the findings from the Potential of Mean Force (PMF) analysis. The outcomes obtained using the Surface Complex Formation Model (SCFM) highlight the dominance of the coulombic force ΔG0coul as the principal component of the adsorption energy (ΔG0ads). This work garnered insights into the adsorption mechanism by meticulously examining the ΔG0ads across a pH ranging from 4 to 8. In essence, this study's findings furnish crucial insights for the future design of analogous adsorbents, thereby advancing the realm of uranium(VI) removal methodologies. [ABSTRACT FROM AUTHOR]

The accurate determination of uranium content in geological samples is extremely important for the exploration and development of uranium resources. In this study, based on titration method for the determination of uranium content of the nuclear industry standard test, the pretreatment process such as sample dissolution, sample dissolution reagent and test method has been improved according to the characteristics of geological samples. The results showed that the sample was moistened with water before acid treatment, and the dissolving vessel was adjusted from 100 mL beaker to 150 mL triangle flask, which basically avoided the problem of sputtering during the boiling process. The amount of phosphoric acid added in the sample dissolution reagent was increased to ensure that the ferrous could completely reduce the hexavalent uranium in the sample at the appropriate phosphoric acid concentration, and the low measurement result caused by the low phosphoric acid concentration is avoided. In the test, the amount of reducing agent ferrous sulfate is changed to 1 mL, and the amount of sodium nitrite was changed to 3–4 drops, which improved the sensitivity of titration endpoint and realized clear determination of titration end point. The RSD of the improved test method is better than 2.5%, and the standard recovery is between 99 and 102%. The results are accurate and reliable, can meet the needs of scientific research and production. It can provide technical support for uranium exploration and natural uranium production. [ABSTRACT FROM AUTHOR]

As UO2 is easily oxidized during the nuclear fuel cycle it is important to have a detailed understanding of the structures and properties of the oxidation products. Experimental work over the years has revealed many stable uranium oxides including UO2, U4O9 (UO2.25), U3O7 (UO2.33), U2O5 (UO2.5), U3O8 (UO2.67), and UO3, all with a number of different polymorphs. These oxides are broadly split into two categories, fluorite-based structures with stoichiometries in the range of UO2 to UO2.5 and less dense layered-type structures with stoichiometries in the range of UO2.5 to UO3. While UO2 is well characterized, both experimentally and computationally, there is a paucity of data concerning higher stoichiometry oxides in the literature. In this work we determine the ambient melting points of all the six stoichiometric uranium oxides listed above and compare them to the available experimental and/or theoretical data. We demonstrate that a family of the six ambient melting points map out a solid-liquid transition boundary consistent with the high-temperature portion of the phase diagram of uranium-oxygen system suggested by Babelot et al. [ABSTRACT FROM AUTHOR]

A hydrothermal and ethanol activation method is proposed to synthesize Cu-BTC and graphite oxide composites (Cu-BTC/GO). The uranium dynamic adsorption behavior was investigated by varying the addition of graphene oxide. The result showed that Langmuir isotherm and quasi-secondary kinetic model (R2 > 0.99) were more consistent with the adsorption process of uranium (VI) on this composite, and the maximum uranium adsorption was 150.50 mg g−1. The thermodynamic parameters indicated that this adsorption process was spontaneous and endothermic. After five adsorption–desorption cycles, the adsorption efficiency can still reach 76.6–78.9%. This study will help to draw a promising roadmap to describe the adsorption performance of Cu-BTC/GO composites for uranium. [ABSTRACT FROM AUTHOR]

Reactions of atomic uranium cations with carbon disulfide form US+ in an efficient exothermic reaction and UCS+ in an inefficient endothermic process. The subsequent reaction of US+ with CS2 forms US2+ in an endothermic process having a low energy threshold. At much higher energies, UCS2+ and UCS+ are also formed. Collision-induced dissociation of US+ with Xe yields U+ + S exclusively in an endothermic reaction. Analysis of the kinetic energy dependent cross sections of the endothermic processes yields the 0 K bond dissociation energies of 5.73 ± 0.15 eV for U+ – S, 3.89 ± 0.08 eV for SU+ – S, 1.69 ± 0.17 eV for U+ – CS, 2.78 ± 0.33 eV for U+ – CS2, 1.53 ± 0.30 eV for SU+ – CS, and 5.65 ± 0.39 eV for S – UCS+. Theory is used to explore the structures and electron configurations of US+, US2+, UCS+, and UCS2+. The thermochemistry measured in this study is further compared to analogous values previously determined for select group 3 metals, lanthanides, and actinides. [ABSTRACT FROM AUTHOR]

Effective treatment of uranium-containing wastewater is of great significance to the sustainable development of nuclear power and the protection of ecological environment. In this study, a highly efficient uranium adsorbent, graphene oxide (GO)/nano-hydroxyapatite (nHA) composite microspheres (nHA@rGO) was synthesized, which could effectively remove uranium from aqueous solution. Under the condition of pH = 3.5, T = 298 K, the maximum adsorption capacity reached 1672.96 mg/g. The results of batch experiments showed that the adsorption capacity of nHA@rGO microspheres was higher than that of nHA microspheres, indicating the enhancement of GO. The adsorption kinetics conformed to the pseudo second-order model. The changes of nHA@rGO microspheres before and after uranium adsorption were analyzed by FT-IR, XPS and XRD. The mechanisms of U(VI) ions adsorption onto nHA@rGO microspheres involved precipitation, surface complexation and ion exchange, in which the hydroxyl and phosphoric acid groups played important roles. The results showed that the prepared nHA@rGO microspheres can be used as an efficient and promising adsorbent for the treatment of uranium-containing wastewater. [ABSTRACT FROM AUTHOR]

Reactions of atomic uranium cations with carbon disulfide form US+ in an efficient exothermic reaction and UCS+ in an inefficient endothermic process. The subsequent reaction of US+ with CS2 forms US2+ in an endothermic process having a low energy threshold. At much higher energies, UCS2+ and UCS+ are also formed. Collision-induced dissociation of US+ with Xe yields U+ + S exclusively in an endothermic reaction. Analysis of the kinetic energy dependent cross sections of the endothermic processes yields the 0 K bond dissociation energies of 5.73 ± 0.15 eV for U+ – S, 3.89 ± 0.08 eV for SU+ – S, 1.69 ± 0.17 eV for U+ – CS, 2.78 ± 0.33 eV for U+ – CS2, 1.53 ± 0.30 eV for SU+ – CS, and 5.65 ± 0.39 eV for S – UCS+. Theory is used to explore the structures and electron configurations of US+, US2+, UCS+, and UCS2+. The thermochemistry measured in this study is further compared to analogous values previously determined for select group 3 metals, lanthanides, and actinides. [ABSTRACT FROM AUTHOR]

Uranium diazomethanediide complexes can be prepared and their synthesis, structure and reactivity were explored. Reaction of the uranium imido compound [η5‐1,2,4‐(Me3Si)3C5H2]2U=N(p‐tolyl)(dmap) (1) or [η5‐1,3‐(Me3C)2C5H3]2U=N(p‐tolyl)(dmap) (4) with Me3SiCHN2 cleanly yields the first isocyanoimido metal complexes [η5‐1,2,4‐(Me3Si)3C5H2]2U(=NNC)(μ‐CNN=)U(dmap)[η5‐1,2,4‐(Me3Si)3C5H2]2 (2) and {[η5‐1,3‐(Me3C)2C5H3]2U[μ‐(=NNC)]}6 (5), respectively. Both compounds exhibit remarkable thermal stability and were fully characterized. According to density functional theory (DFT) studies the bonding between the Cp2U2+ and [NNC]2− moieties is strongly polarized with a significant 5 f orbital contribution, which is also reflected in the reactivity of these complexes. For example, complex 5 acts as a nucleophile toward alkylsilyl halides and engages in a [2+2] cycloaddition with CS2, but no reaction occurs in the presence of internal alkynes. [ABSTRACT FROM AUTHOR]

A promising way to recover spent nuclear fuel (SNF) is the method of extracting transuranium compounds from molten salt, which makes it possible to obtain a partial separation between transuranium compounds and lanthanides. This work is devoted to the quantum mechanical study of changes in the structure, energy and electronic properties of the main SNF component, uranium dioxide, upon the removal of oxygen from the system. The influence of the considered properties on the substitution of uranium by plutonium is also studied at a ratio, of the number of plutonium atoms to uranium atoms, of 1:7 and 1:3. The removal of oxygen leads to a narrowing of the band gap up to the transition to a conductive state at a ratio of uranium to oxygen of 2:3. The band gap narrows and metallization sets in even when uranium is replaced by plutonium. A two-stage UO2 metallization scheme based on lithium reduction and direct (electronic) reduction is proposed. [ABSTRACT FROM AUTHOR]

Three new cross-linked chitosan derivatives were yielded through intensification of chitosan with diverse types of bis-aldehydes. The prepared cross-linked chitosan was characterized by FTIR, 1H NMR, XRD, and TGA techniques. TGA indicated an improvement in thermal stability of the cross-linked chitosan compared with pure chitosan. Batch adsorption experiments showed that the three novel cross-linked chitosan bis-aldehyde derivatives possessed good adsorption capacity against U(VI) in the order of BFPA > BFB > BODB (adsorption capacity of the three adsorbents for U(VI) reaches 142, 124, and 114 mg/g respectively) and the adsorption isotherm and kinetic were well described by the Langmuir and the pseudo-second-order kinetic model, respectively. In addition, the prepared cross-linked chitosan bis-aldehyde derivatives were examined as U(VI) catcher from waste solutions. [ABSTRACT FROM AUTHOR]

The Lewis base-supported uranium terminal imido metallocene [η5-1,2,4-(Me3Si)3C5H2]2UvN(p-tolyl) (dmap) (1) readily reacts with various small molecules such as internal alkynes, isothiocyanates, thioketones, amidates, organic nitriles and imines, chlorosilanes, copper iodide, diphenyl disulfide, organic azides and diazoalkane derivatives. For example, treatment of 1 with PhCuCCuCPh and PhNCS forms metallaheterocycles originating from a [2 + 2] cycloaddition to yield [η5-1-(p-tolyl)NC(Ph)vCHCvC(Ph) CH2Si(Me)2-2,4-(Me3Si)2C5H2][η5-1,2,4-(Me3Si)3C5H2]U (2) and [η5-1,2,4-(Me3Si)3C5H2]2U[N(p-tolyl)C (vNPh)S](dmap) (3), respectively. The reaction of 1 with the thioketone Ph2CS forms the known uranium sulfido complex [η5-1,2,4-(Me3Si)3C5H2]2US(dmap) (4), which reacts with a second molecule of Ph2CS to give the disulfido compound [η5-1,2,4-(Me3Si)3C5H2]2U(S2CPh2) (5). The imido moiety also promotes deprotonation reactions as illustrated in the reactions with the amide PhCONH(p-tolyl), the nitrile PhCH2CN and the imine (p-tolyl)2CvNH to form the bis-amidate [η5-1,2,4-(Me3Si)3C5H2]2U[OC(Ph)N(ptolyl)] 2 (7), and the iminato complexes [η5-1,2,4-(Me3Si)3C5H2]2U[N(p-tolyl)C(CH2Ph)vNH](NvCvCHPh) (8) and [η5-1,2,4-(Me3Si)3C5H2]2U[NH(p-tolyl)][NvC(p-tolyl)2] (9), respectively. Addition of PhSiH2Cl to 1 yields [η5-1,2,4-(Me3Si)3C5H2]2U(Cl)[N(p-tolyl)SiH2Ph] (10). In contrast, the uranium(V) imido complexes [η5-1,2,4-(Me3Si)3C5H2]2UvN(p-tolyl)(I) (11) and [η5-1,2,4-(Me3Si)3C5H2]2UvN(p-tolyl)(SPh) (12), may be isolated upon addition of CuI or Ph2S2 to 1, respectively. Uranium(VI) bis-imido metallocenes [η5-1,2,4-(Me3Si)3C5H2]2UvN(p-tolyl)(vNR) (R = p-tolyl (13), mesityl (14)) and [η5-1,2,4-(Me3Si)3C5H2]2UvN(ptolyl)[ vNNv(9-C13H8)] (15) are accessible from 1 on exposure to RN3 (R = p-tolyl, mesityl) and 9-diazofluorene, respectively. Complexes 2, 3, 5, and 7-15 were characterized by various spectroscopic techniques and, in addition, compounds 2, 3, 5, and 7-13 were structurally authenticated by single-crystal X-ray diffraction analyses. [ABSTRACT FROM AUTHOR]

The Mayer group expansion method is extended on the low-temperature solids where quantum effects cannot be ignored and applied to the prediction of polymorphic transition line between cubic Fm3m and orthorhombic Pnma phases in the highly compressed ionic crystal of uranium dioxide. The temperature dependence of the transition pressure and volume changes are evaluated and the results are compared with existing experimental data and ab initio predictions. [ABSTRACT FROM AUTHOR]

Tri-iso-amyl phosphate (TiAP) is a promising alternative extract agent to tri-n-butyl phosphate for spent fuel reprocessing. In this work, the effect of concentration and dominant radiolysis products of TiAP in γ-irradiated TiAP/n-dodecane (nDD) solution on the extraction of UO2(NO3)2 was investigated. The extraction efficiency of U(VI) increased significantly with absorbed dose in the absence of nitric acid due to the formation of di-iso-amyl phosphoric acid (HDiAP). Density functional theory calculation further proved that coordination energy between HDiAP and U(VI) is higher than that of TiAP. Extraction performance confirmed the synergistic effect of TiAP and HDiAP on U(VI). [ABSTRACT FROM AUTHOR]

A poly(toluidine blue) modified glassy carbon electrode (PTB/GCE) was prepared by two-step electropolymerization, and was used for the stripping voltammetric analysis of trace uranium for the first time. The results showed that the PTB modified electrode had higher sensitivity of uranium detection compared with the glassy carbon electrode, and the standard addition method was satisfactory for seawater, river water and tap water. The PTB/GCE can be used as a mercury-free electrode for the electrochemical detection of uranyl ions in the environmental water, which provides a new way for the rapid detection of trace uranium. [ABSTRACT FROM AUTHOR]

Understanding the binding configuration of uranium on biotite is crucial for elucidating the environmental behavior of U(VI) and addressing emergency scenarios in disposal repositories. This investigation demonstrated that U(VI) adsorption on biotite was significantly affected by pH, while a lesser impact from ionic strength. Moreover, the presence of phosphate and humic acid (HA) exerted a substantial enhancing influence on U(VI) adsorption (adsorption rate increased by over 20%). X-ray photoelectron spectroscopy (XPS) analysis revealed that elevated Fe(II) contents within biotite structures facilitated the reduction of partial U(VI) to form U(V/IV)/U(IV), i.e., mineralization products, under both aerobic and anaerobic conditions. [ABSTRACT FROM AUTHOR]

2-(((2,7-Dihydroxynaphthalen-1-yl)methylene)amino)-3′,6′-bis(ethylamino)-2′,7′-dimethylspiro[isoindoline-1,9′-xanthen]-3-one was synthesized using Rhodamine 6G hydrazide (prepared using literature methods) and commercially available 2,7-dihydroxynaphthalene-1-carbaldehyde via imine condensation. Structural characterization was performed using FT-IR, 1H-NMR, 13C-NMR, X-ray, and HRMS. This Schiff base shows promise as a ligand for the colorimetric analysis of uranium in water. [ABSTRACT FROM AUTHOR]

Two new disulfatouranylates, Rb2[UO2(SO4)2(H2O)]⋅1.75H2O (I) and (N2H5)2[UO2(SO4)2(H2O)] (II), were synthesized and their structures were determined by single-crystal X-ray diffraction. In structures I and II, each uranyl ion is coordinated in the equatorial plane by four bidentate-bridging sulfate groups and one water molecule to form pentagonal-bipyramidal complexes with the crystal-chemical formula АВ М1 (A = , B2 = , M1 = H2O). It was found that, while having the same composition [UO2(SO4)2(H2O)]2–, the uranium-containing structural units are geometric isomers, which have a chain and layered structure in I and II, respectively. [ABSTRACT FROM AUTHOR]

The authors synthesized a series of functionalized diatomite-based materials and assessed their U(VI) removal performance. Phosphor-derivative-modified diatomite adsorbents were synthesized by the three-route procedures: polymerisation (DIT-Vin-PAin), covalent (DIT-Vin-PAcov), and non-covalent (DIT-PA) immobilization of the functional groups. The effects of the diatomite modification have been studied using powder XRD, solid state NMR, FTIR spectroscopy, electronic microscopy, EDX, acid–base titrations, etc. The maximum adsorption capacities of DIT-Vin-PAcov, DIT-PA, and DIT-Vin-PAin samples were 294.3 mg/g, 253.8 mg/g, and 315.9 mg/g, respectively, at pH0 = 9.0. The adsorption amount of U(VI) ions using the prepared DIT-Vin-PAin was 95.63%, which is higher compared with that of the natural diatomite at the same concentration. The adsorption studies demonstrated that the phosphonic and hydroxyl groups on the surface of the diatomite played pivotal roles in the U(VI) adsorption. The U(VI) ions as a "hard" Lewis acid could easily form bonds with the "hard" donor P-containing ligands, so that the as-prepared DIT-Vin-PAin sample had excellent adsorption properties. The monolayer adsorption of the analyte on the surface of the raw diatomite and DIT-PA was observed. It was found from the thermodynamic parameters that the uptake of the U(VI) ions by the obtained adsorbents was a spontaneous process with an endothermic effect. Findings of the present work highlight the potential for using modified diatomite as effective and reusable adsorbents for the extraction of U(VI) in the waste, river, and tap waters with satisfactory results. [ABSTRACT FROM AUTHOR]

Contamination of underground water by uranium (U) and other heavy metals is a growing concern. Mesoporous silica nanoparticles (MSNs) have shown great potential as an adsorbent material for heavy metal removal. This study synthesized a novel MSN using surface-initiated atom transfer radical polymerization (SI-ATRP) and evaluated its effectiveness for removing uranium from aqueous solutions under different conditions. The particle size was reduced to 150–240 nm to enhance adsorption. Fourier transform infrared characterization and thermogravimetric analysis confirmed successful synthesis and modification. Results showed that the MSN adsorbent was highly effective in removing U, with a removal rate of 85.35% at 120 min. Temperature had a significant impact, with the highest removal rate of 96.7% achieved at 25 °C and a U concentration of 10 ppm. The highest removal rate of 91.89% was achieved at a pH of 6 and a U concentration of 50 ppm. The highest removal rate of 95.16% was achieved at 25 mg and a U concentration of 50 ppm at room temperature for 60 min. The MSNs also showed a 58.27% removal rate in a mixture solution at room temperature for 60 min. This study demonstrates the effectiveness of the MSN adsorbent for removing U under different conditions. [ABSTRACT FROM AUTHOR]

Although barium(II) ions play an important role in the natural weathering of the mineral uraninite (UO2+x) and are expected to therefore do the same for spent nuclear fuel in geological disposal, the detailed structural understanding of this role is rather limited. In this work, we report the synthesis and characterisation of two new uranium oxide hydrate (UOH) phases with barium(II) ions, a layer-structured UOH-Ba1 constructed with undulating uranyl oxide hydroxide layers incorporating hydrated interlayer barium(II) ions; and UOH-Ba2 forming a complex three-dimensional structure by linking six different types of uranium polyhedrons with barium(II) ions located in the narrow channels. Both crystal structures were revealed using synchrotron single crystal X-ray diffraction and confirmed with powder X-ray or electron diffractions. While vibrational modes were elucidated by Raman, electronic structures and the presence of pentavalent uranium were investigated using diffuse reflectance spectroscopy. This work has provided insights into the complexity of uranium crystal chemistry in the presence of barium(II) ions and has implications to both uranium geochemistry in terms of the natural weathering of uraninite and the disposal of spent nuclear fuel in the underground repository. [ABSTRACT FROM AUTHOR]

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. The synthesis of sp2 carbon-conjugated covalent organic frameworks is limited to a few reactions and monomers due to the poor irreversibility of carbon double bonds. Here the authors synthesize propenone-linked covalent organic frameworks for the removal of radionuclide uranium from mine wastewater samples. [ABSTRACT FROM AUTHOR]

Uranium and thorium are heavy metals, and all of their isotopes are radioactive, so it is impossible to study chemical effects entirely independent of the radiation effects. In the present study, we tried to compare the chemo- and radiotoxicity of both metals, taking into account deterministic radiation damages reflected by acute radiation sickness and stochastic radiation damages leading to long-term health impairments (e.g., tumor induction). We made at first a literature search on acute median lethal doses that may be expected to be caused by chemical effects, as even acute radiation sickness as a manifestation of acute radiotoxicity occurs with latency. By simulations based on the biokinetic models of the International Commission on Radiological Protection and using the Integrated Modules for Bioassay Analysis software, we determined the amounts of uranium at different enrichment grades and thorium-232 leading to a short-term red bone marrow equivalent dose of 3.5 Sv considered to cause 50% lethality in humans. Different intake pathways for incorporation were considered, and values were compared to the mean lethal doses by chemotoxicity. To assess stochastic radiotoxicity, we calculated the uranium and thorium amounts leading to a committed effective dose of 200 mSv that is often considered critical. Mean lethal values for uranium and thorium are in the same order of magnitude so that the data do not give evidence for substantial differences in acute chemical toxicity. When comparing radiotoxicity, the reference units (activity in Bq or weight in g) must always be taken into account. The mean lethal equivalent dose to the red bone marrow of 3.5 Sv is reached by lower activities of thorium compared to uranium in soluble compounds. However, for uranium as well as thorium-232, acute radiation sickness is expected only after incorporation of amounts exceeding the mean lethal doses by chemotoxicity. Thus, acute radiation sickness is not a relevant clinical issue for either metal. Concerning stochastic radiation damages, thorium-232 is more radiotoxic than uranium if incorporating the same activities. Using weight units for comparison show that for soluble compounds, thorium-232 is more radiotoxic than low-enriched uranium in the case of ingestion but even more toxic than high-enriched uranium after inhalation or intravenous administration. For insoluble compounds, the situation differs as the stochastic radiotoxicity of thorium-232 ranges between depleted and natural uranium. For acute effects, the chemotoxicity of uranium, even at high enrichment grades, as well as thorium-232 exceeds deterministic radiotoxicity. Simulations show that thorium-232 is more radiotoxic than uranium expressed in activity units. If the comparison is based on weight units, the rankings depend on the uranium enrichment grades and the route of intake. [ABSTRACT FROM AUTHOR]

Montmorillonite-supported nanoscale zero-valent iron composite functionalized by thiols (nZVI/Mt-SH) was synthesized by a two-step co-precipitation method for uranium (IV) removal from water. The SEM investigation showed that the morphology of nZVI/Mt was successfully modified by the (3-Mercaptopropyl) trimethoxysilane. The optimal adsorption efficiencies could be attributed to the synergetic behavior between SH-functionalized clay and iron nanoparticles. Analysis of the removal kinetics indicated the feature of monolayer chemisorption. The intraparticle diffusion exploration by Weber-Morris model illustrated a multi-phase removal process. This work suggests that the as-synthesized particles could be used as an efficient adsorbent to remove U(VI) from contaminated water sources. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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During nuclear fuel processing, workers can potentially be exposed to repeated inhalations of uranium compounds. Uranium nephrotoxicity is well documented after acute uranium intake, but it is controversial after long-term or protracted exposure. This study aims to analyze the nephrotoxicity threshold after repeated uranium exposure through upper airways and to investigate the resulting uranium biokinetics in comparison to reference models. Mice (C57BL/6J) were exposed to uranyl nitrate (0.03–3 mg/kg/day) via intranasal instillation four times a week for two weeks. Concentrations of uranium in urines and tissues were measured at regular time points (from day 1 to 91 post-exposure). At each exposure level, the amount of uranium retained in organs/tissues (kidney, lung, bone, nasal compartment, carcass) and excreta (urine, feces) reflected the two consecutive weeks of instillation except for renal uranium retention for the highest uranium dose. Nephrotoxicity biomarkers, KIM-1, clusterin and osteopontin, are induced from day 4 to day 21 and associated with changes in renal function (arterial fluxes) measured using non-invasive functional imaging (Doppler-ultrasonography) and confirmed by renal histopathological analysis. These results suggest that specific biokinetic models should be developed to consider altered uranium excretion and retention in kidney due to nephrotoxicity. The threshold is between 0.25 and 1 mg/kg/day after repeated exposure to uranium via upper airways. [ABSTRACT FROM AUTHOR]

A major challenge for radioactive wastewater treatment and associated environmental remediation is how to simultaneously remove cationic and anionic radionuclides. Herein, a series of Mn3O4@polyaniline (Mn3O4@PANI) nanocomposites were successfully prepared and used to remove U(VI) and I− from aqueous solution, two highly concomitant species in nuclear pollution settings. Batch adsorption experiments reveal that the component Mn3O4 is predominantly responsible for U(VI) removal, but PANI for I−. The nanocomposite with 24.2 wt% Mn3O4 possesses high removal percentages (> 85%) either for U(VI) or I− over a wide pH range, fast removal kinetics, and excellent adsorption selectivity at high concentrations of competing ions. Benefiting from the contributions of the two components and the high adsorption affinities, the nanocomposite achieves the simultaneous removal to coexisting U(VI) and I−, with a maximum adsorption capacity 102.6 mg/g for U(VI) and 126.1 mg/g for I−. X-ray photoelectron spectroscopy (XPS) results reveal that the U(VI) adsorption occurs via coordination bonding with Mn−O, −NH− , and =N− groups in the nanocomposite, whereas I− adsorption proceeds mainly through I anionic species exchange with Cl− and interactions with π-bonds in PANI, as well as the electrostatic attraction onto Mn3O4. Considering the excellent performance and multiple active sites, the Mn3O4@PANI nanocomposite is promising to remove practical radioactive U(VI) and I−. [ABSTRACT FROM AUTHOR]

A novel and really simple method for extractive photometric determination of uranium is achievable by Azur II dye with accurate and sensitive results. This has been possible through a basic dye (Azur II) that reacts firstly with a suitable ligand (benzoate) to form a triple complex. The latter is then extracted in a suitable organic solvent (Trioctylamine). Optimisation of the formed U-benzoate-Azur II complex was performed by studying several parameters such as suitable pH, dye concentration, duration time of the formed complex, solvent concentration, shaking time and U concentration (calibration curve). This reagent is extremely sensitive to uranium, with a molar absorption potential of 0.654 × 104 L. M−1 cm−1 at pH 4 at 688 nm. Absorbance measurements showed as time function that the coloured complex is stable up to 20 min. This system allows uranium content to be calculated with a detection limit (LOD) of 0.15 µg L−1, and precision expressed as relative standard deviation (RSD) of 0.368%. The tolerance limits had been calculated for several metal ions. Accuracy was confirmed by U (VI) determination in the standard reference materials. This new spectrophotometric method was applied for the determination of U(VI) in some cataclastic rock samples with accurate results. [ABSTRACT FROM AUTHOR]

Tailoring the band structure of photocatalysts by elemental doping to enhance redox ability and carrier separation kinetics is a promising strategy for designing high-efficiency catalysts for uranium (U(VI)) photoreduction. Herein, we report enhanced visible-light spectral absorption by tuning the energy bandgap of flower-like ZnO microspheres by doping Co. Accordingly, Co doping narrows the bandgap and increases the photogenerated carrier concentration, thereby promoting the U(VI) photocatalytic reduction. Especially, the removal ratio of U(VI) by Co-doped ZnO microspheres reaches 98.4% with a remarkable adsorption capacity of 1645 mg/g for U(VI) uptake in 400 ppm U(VI) solution. In addition, the Co-doped ZnO microspheres present desired U(VI) reduction ratio in a wide range of U(VI) concentrations, as well as excellent reusability, and resistance to ion interference during photocatalysis. This paper provides a feasible strategy for enhancing the photocatalytic reduction of uranium by introducing metal element doping on the metal oxide surface. [ABSTRACT FROM AUTHOR]

For uranium adsorption in water, a new uranium adsorbent was synthesized by preparing poly(tetraethylenepentamine–trimesoyl chloride). The samples were characterized using SEM, EDS, TGA, FTIR and XPS. The removal ability and adsorption mechanism of uranium (VI) in an aqueous solution by poly(tetraethylenepentamine–trimesoyl chloride) were systematically studied. The results showed that the adsorption equilibrium was completed within 80 min, the adsorption capacity reached 189.82 mg g−1, and the removal rate reached 94.91%. The adsorption process fitted well with the pseudo-second-order model and the Langmuir isotherm model. The thermodynamic analysis indicated that the adsorption was an endothermic and spontaneous process. This study proved that poly(tetraethylenepentamine–trimesoyl chloride) could be considered a highly efficient and sustainable material for the removal of uranium (VI) from aqueous solutions. [ABSTRACT FROM AUTHOR]

This work presents the results of studies of extraction properties in relation to the uranium of bis(2,2,2-trifluoroethyl)diallylamido phosphite, bis(2,2,2-trifluoroethyl)dimethylamido phosphite, and bis(N, Ndialamido) isopropyl phosphite synthesized by us earlier. Tests were carried out in a factory laboratory, as the initial solutions used nitrate solution prepared from uranium oxide (CU = 10.30 g/dm3, CHNO3 = 56.40 g/dm3) and uranium sulfate solution prepared from the chemical concentrate of natural uranium and deoxidized with sulfuric acid (CU = 10.60 g/dm3, CH2SO4 = 25.10 g/dm3). It was proved that the synthesized acyclic amido phosphites can effectively extract uranium from these technological solutions with a proper selection of technological parameters, and the degree of uranium extraction may vary from 34.43 to 95.94%. [ABSTRACT FROM AUTHOR]