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The investigation of interaction mechanism of U(VI) selective removal on amidoxime-functionalized metal organic framework (i.e., UiO-66(Zr)-AO) derived from macromolecular carbohydrate is conducive to apply metal organic frameworks in actual environmental remediation. The batch experiments showed that UiO-66(Zr)-AO displayed the fast removal rate (equilibrium time of 0.5 h), high adsorption capacity (384.6 mg/g), excellent regeneration performance (<10 % decrease after three cycles) towards U(VI) removal due to the unprecedented chemical stability, large surface area and simple fabrication. U(VI) removal at different pH can be satisfactorily fitted by diffuse layer modeling with cation exchange at low pH and an inner-sphere surface complexation at high pH. The inner-sphere surface complexation was further demonstrated by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analysis. These findings revealed that UiO-66(Zr)-AO can be an effective adsorbent to remove the radionuclides from aqueous solution, which is crucial for recycling of uranium resource and decreasing the uranium harm to the environment., Competing Interests: Declaration of competing interest There are no conflicts of interest to declare., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The Chinese Bayan Obo deposit is a world-class rare earth element (REE) deposit with considerable niobium (Nb) and iron (Fe) resources. A complete genetic understanding on all metals is fundamental for establishing genetic models at Bayan Obo. With extensive research being focused on REE enrichment, the timing and controls of Nb enrichment remain unresolved at Bayan Obo, which is mainly due to the challenges in dating, i.e. multistage thermal events, fine-grained minerals with complex textures and the rare occurrence of uranium-enriched minerals with mature dating methods. Based on robust geological and petrographic frameworks, here we conducted ion probe uranium-lead (U-Pb) dating of ferrocolumbite to unravel the timing, hence the genesis of Nb mineralization. Three types of hydrothermal ferrocolumbites—key Nb-bearing minerals—are identified based on their textures and mineral assemblages. They yield U-Pb ages of 1312 ± 47 Ma (n  = 99), 438 ± 7 Ma (n  = 93), and 268 ± 5 Ma (n  = 19), respectively. In line with deposit geology, we tentatively link the first, second and third stage Nb mineralization to Mesoproterozoic carbonatite magmatism, ubiquitous early Paleozoic hydrothermal activity, and Permian granitic magmatism, respectively. While quantifying the contribution of metal endowment from each stage requires further investigation, our new dates highlight that multi-stage mineralization is critical for Nb enrichment at Bayan Obo, which may also have implications for the enrichment mechanism of Nb in REE deposits in general. [ABSTRACT FROM AUTHOR]

Glass solidification is a common method for curing highly radioactive waste liquid. This method has the advantages of high resistance to chemical corrosion, and good radiation, thermal, and mechanical stability. However, the disadvantage is the decline of resistance to water leaching so that the reliability of the result needs to be confirmed by an anti-leaching test. Using Secondary Ionization Mass Spectrometry (SIMS) to analyze the composition distribution and leaching behavior of radioactive components (such as uranium) in the solid glass is a method for evaluating the ability of resistance to leaching of solidified glass. The simulated glass solidified sample was tested by SIMS and the results are reported and discussed in this paper. Carbon was used as the coating material during vacuum evaporation coating on the surface of the sample in order to overcome the poor conductivity of the sample. The isotopic composition of natural uranium is about 7.3‰. And the ratio of 235U/238U in the prepared solid glass is 7.9‰±0.395‰. The research indicates that the method can determine the measurement of the isotopic abundance of uranium and directly show its distribution. This method can provide technical support for the study of the leaching behavior of radioactive elements in solidified glass samples.

The determination of isotope ratios in individual uranium particles is very important for nuclear safeguards. In this work, accelerator mass spectrometry (AMS), thermal ionization mass spectrometry (TIMS), and secondary ion mass spectrometry (SIMS) were applied to isotope ratio analysis of individual uranium particles and compared in terms of background, measurement accuracy, and efficiency. Several individual uranium particles (1–7 μm) from certified reference materials were used as samples. The results show that the average values of blank counting rate of 235U for AMS, FT‐TIMS (FT: fission track), SEM‐TIMS (SEM: scanning electron microscope), and SIMS were 7.3, 7.8, 2.7 and 2.2 cps, respectively. The relative error of 234U/235U and 234U/236U isotope ratios of the particles from U200 for AMS were within 10% and 20%, whereas the results of FT‐TIMS and SIMS were within 5% and 10%, respectively. The relative error and external precision of 234U/238U and 235U/238U of the particles from U850 for the method of AMS, SEM‐TIMS, and SIMS were within 10% and 5%, respectively. For 236U/238U, the average values of the relative error and external precision measured by AMS were within 5%, which measured by SEM‐TIMS and SIMS were all within 10%. AMS has advantages in measuring 236U/238U. The measurement time of AMS and SEM‐TIMS was shorter than that of FT‐TIMS and longer than that of SIMS. It is considered that AMS and SEM‐TIMS have a certain development prospect, and it is necessary to research deeply. [ABSTRACT FROM AUTHOR]

Developing different model age determination methods of uranium sample could get more information on insight into source and suspected use in nuclear forensic investigation. A procedure for the determination of model age of uranium sample using 231Pa/235U radiochronometer was reported. The 233Pa spike used in the procedure of 231Pa–235U model age determination was separated from in-house 237Np stock solution by using two TRU resin columns and three silica gel columns and calibrated by CRM U100. Model ages of CRM U010 and IRMM-1000b were presented. The model age of IRMM-1000b using 231Pa/235U radiochronometer were older than the literature reported results by 230Th/234U radiochronometer by amounts exceeded the expanded uncertainty. [ABSTRACT FROM AUTHOR]

Th/U radiochronometer was commonly used for uranium age determination which could help to reveal the origin of the nuclear material. Th was a relatively appropriate spike for measuring Th by isotope dilution mass spectrometry and its concentration needs to be calibrated before using as spike. A prepared Th solution which was used as Th isotope spike for age dating of CRM U850 sample were calibrated separately by Th and Th standard materials. The calibrated results were compared and evaluated. [ABSTRACT FROM AUTHOR]

Abstract: Isotopic ratio of single uranium-bearing particle in swipe samples was very important for safeguards environmental sampling. For this purpose, an improved FT-TIMS method was developed in this work: (1) Uranium-bearing particles are suspended in the solution of cellulose nitrate commixed with isoamyl acetate, and then spread onto a glass surface, the solution was dried to form a transparent film; (2) After irradiating and etching, uranium-bearing particles can be found and located under microscope. The small part of the film contained one uranium-bearing particle is then cut off and transferred to a filament of TIMS; (3) Isotopic ratio of the particle is determined by TIMS. The problem of particles losing has been avoided in the process of sample preparing, particle locating and transferring. The deviation of the result from the certified value of CRM was less than 5%. [Copyright &y& Elsevier]