Latest ArticlesUranium removal from aqueous solutions using environmentally friendly photocatalytic technology is a novel approach for resource recovery. Herein, carbon nitride/activated carbon composite materials (CN/AC) were investigated for U(Ⅵ) reduction under visible light. An exceptional boost in photocatalytic activity was observed for CN/AC composites (up to 70 times over the conventional bulk g-C3N4). The strong interactive conjugated π-bond structure between g-C3N4 and AC accelerated the migration of carriers and then prolonged the electron lifetime. CN/AC composites exhibited excellent compatibility with different water substrates and were resilience to a wide range of pH changes and abundant competitive anions/cations. Quenching experiments and electron microscopy characterization indicated that U(Ⅵ) was reduced by photogenerated electrons and deposited on the edge of CN/AC composites. The low-cost, high-performance carbon-based composite material proposed in this work is a potential candidate for the efficient treatment of radioactive wastewater.
Separation and recovery of U(Ⅵ) and Th(Ⅳ) from rare earth minerals is a very challenging work in rare earth industrial production. In the present study, a homemade membrane emulsification circulation (MEC) extractor was used to separate U(Ⅵ) and Th(Ⅳ) from rare earth elements by using Cyphos IL 104 as an extractant. Batch experiments were carried out using a constant temperature oscillator to investigate the extraction parameters of the single element and the results indicated that Cyphos IL 104 could reach the extraction equilibrium within 30 min for all the three elements, i.e., U(Ⅵ), Th(Ⅳ), and Eu(Ⅲ). Besides, the MEC extractor possessed a strong phase separation ability. The extraction efficiencies of U(Ⅵ), Th(Ⅳ), La(Ⅲ), Eu(Ⅲ) and Yb (Ⅲ) increased with the increase of pH. La(Ⅲ), Eu(Ⅲ) and Yb(Ⅲ) were hardly extracted when pH ≤ 1.50, which was beneficial for effectively separating U(Ⅵ) and Th(Ⅳ) from La(Ⅲ), Eu(Ⅲ) and Yb(Ⅲ). In the multi-stages stripping experiments, when the stripping stage number was 3, the effective separation could be achieved by using HCl and H2SO4, since the stripping efficiency reached 80.0% and 100.0% for Th(Ⅳ) and U(Ⅵ), respectively. Slope method and FT-IR spectra showed that Cyphos IL 104 reacted with U(Ⅵ) and Th(Ⅳ) by chelation mechanism. The extraction of multi-elements indicated that U(Ⅵ) and Th(Ⅳ) could be well separated from the solution which contains all rare earth elements, and the extraction efficiencies of U(Ⅵ) and Th(Ⅳ) both were close to 100.0%. Based on the above experimental results, a flowchart for efficient separation of U(Ⅵ) and Th(Ⅳ) from rare earth elements was proposed.
Soft N-donor bis-triazin bipyridines derives (R-BTBP) are a type of very promising extratant for extraction and complexation with long-lived trivalent minor actinides over lanthanides from highly active liquid waste (HLW). In addition to minor actinides, R-BTBP also holds very strong complexation ability toward fission palladium. However, few studies have been focused on the separation and complexation with the fission product Pd(Ⅱ) by R-BTBP. Herein, the complexation behaviors of Pd(Ⅱ) with four typical R-BTBP ligands were systematically studied by single crystal X-ray diffraction, 1H NMR titration and theoretical calculation. The effects of R-BTBP initial conformation and nitrate anions on the complexation behaviors of R-BTBP with Pd(Ⅱ) were thoughtfully analyzed. Both the 1:1 and 2:1 binuclear complexes could be formed between Pd(Ⅱ) and R-BTBP with initial Ⅱ conformation in the presence of nitrate anions, while only one 1:1 type Pd(Ⅱ) complex could be formed for those with initial OO conformation. Without nitrate anion, only one 1:1 type complex was formed in solution. The structure of the 1:1 Pd(Ⅱ)/R-BTBP complex was firstly characterized by single crystal crystallography. DFT calculation results showed that a significant large rotational energy barrier (21.8~22.6 kcal/mol) must be overcome to form the Ⅱ type 2:1 Pd(Ⅱ) complex for those OO type R-BTBP ligands, however which would not prevent them from forming the 1:1 type complex.
A relatively new branch of science - nuclear forensics, aiming at providing the nature, origin, history and possible trafficking route of seized nuclear materials/devices, has been established and rapidly developed over decades to screen illicit nuclear activities. This highly interdisciplinary science is built upon a foundation of analytical chemistry, radiochemistry, nuclear physics, material sciences, geology, and other scientific disciplines, within which radiochemical methodologies and radioanalytical techniques play a key role. The present review provides a brief overview about the crucial aspects of nuclear forensics, including basic content, procedure, concerned elements, common separation, analytical method, and so on. The state of the art and recent progresses of nuclear forensics by research communities in China are reviewed, while selected examples and practical applications are emphasized. The challenges associated with this new area and on-going developments are highlighted and discussed.
Heavy haze events have become a serious environment and health problem in China and many developing countries, especially in big cities, like Beijing. However, the factors and processes triggered the formation of secondary particles from the gaseous pollutants are still not clear, and the processes driving evolution and degradation of heavy haze events are not well understood. Iodine isotopes (127I and 129I) as tracers were analyzed in time series aerosol samples collected from Beijing. It was observed that the 127I concentrations in aerosols peaked during the heavy haze events. The conversion of gaseous iodine to particular iodine oxides through photochemical reactions provides primary nuclei in nucleation and formation of secondary air particles, which was strengthened as the external iodine input from the fossil fuel burning in the south/southeast industrial cities and consequentially induced heavy haze events. Anthropogenic 129I concentrations peaked during clean air conditions and showed high levels in spring and later autumn compared to that in summer. 129I originated from the direct air discharges and re-emissions from contaminated seawaters by the European nuclear fuel reprocessing plants was transported to Beijing by the interaction of Westerlies and East Asian winter monsoon. Three types of mechanisms were found in the formation and evolution of heavy haze events in Beijing by the variation of 127I and 129I, i.e., iodine oxides intermediated secondary air particles, dust storm and mixed mode by both secondary air particles and dust storm induced processes.
Tumor-related PD-L2 expression is associated with the clinical efficacy of PD-1/PD-L1 blockade therapy. PD-L2-specific imaging can help selecting patients for appropriate immunotherapy. In this study, a PD-L2-targeting peptide (PDP2) was screened by the one-bead one-compound combinatorial library approach. Using the retro-inverso D-peptide of PDP2 (RD-PDP2) and PEGylation strategies, we developed a novel Tc-99m-labeled PD-L2-targeting peptide as a SPECT tracer (99mTc-PEG6-RD-PDP2) for imaging of tumor PD-L2 expression. The radiolabeling yield of 99mTc-PEG6-RD-PDP2 was greater than 95% by the standard HYNIC/tricine/TPPTS labeling procedure. 99mTc-PEG6-RD-PDP2 displayed high PD-L2-binding specificity both in vitro and in vivo. SPECT/CT imaging with 99mTc-PEG6-RD-PDP2 showed that the A549-PD-L2 tumors were clearly visualized, whereas the signals in PD-L2-negative A549 tumors were much lower. In vivo blocking study suggested that the tumor uptake of 99mTc-PEG6-RD-PDP2 was PD-L2 specifically mediated. 99mTc-PEG6-RD-PDP2 is a promising SPECT probe for the non-invasive imaging of tumor PD-L2 expression and has a great potential in guiding the anti-PD-1 or anti-PD-L1 immunotherapy of cancer.
Abnormal Tau deposition is a crucial pathological hallmark of various neurodegenerative disorders defined as tauopathies, of which Alzheimer's disease is the most prominent one. To date, a large number of chemical entities with different structures have been developed as Tau imaging tracers for the early diagnosis of tauopathies. Several of them with excellent bio-properties are currently being assessed in clinical trials, and more recently, the TauvidTM ([18F]Flortaucipir, also known as [18F]AV1451 or [18F]T807) as the first Tau tracer was approved by the U.S. Food and Drug Administration in 2020. This review summarized the latest development of Tau tracers and analyzed their chemical structures, with particular attention to the effects of chemical structures on biological properties. In addition, we also discuss the limitations of current Tau imaging tracers, issues that need attention in the development of new tracers, and possible future directions.
Targeted alpha-therapy (TAT) is increasingly attractive due to its extraordinary antitumor efficacy. However, the supply of α-emitters for TAT is insufficient and under control by a limited number of countries. 212Pb is a promising α-emitter with an optimal half-life (10.6 h) and favored decay chain. Of interest, 212Pb can be extracted directly from natural thorium, which may be abundant in the mining waste of rare-earth, uranium, etc. Indeed, radioactive thorium waste has been a longstanding environmental challenge that needs immediate action. Developing an on-demand and facile process to isolate 212Pb from natural thorium would be ideal to meet the above challenges, yet is difficult. In theory, the ratio of 212Pb to natTh is below 10−13 in commercially available thorium salts. As a pilot study, 2.2 MBq of 212Pb was successfully extracted from a 5 L solution of thorium nitrate by using a Pb-selective resin. The radiochemical purity of 212Pb is over 99.9% according to gamma-ray analysis. The purified 212Pb was applied to radiolabel a couple of peptides used in clinics (i.e. PSMA, TATE and FAPI-04), and the radiochemical yields are > 85%. Of note, 212Pb can be repeatedly separated from the thorium solution every 2 days. In summary, a practical and scalable method was developed to isolate 212Pb for potentially clinical use, which may be of great importance as it does not require either cyclotron or nuclear reactor.
A process for actinide(Ⅲ) and lanthanum(Ⅲ) extraction separation from high-level liquid waste (HLLW) was proposed, with N,N,N',N'-tetraoctyl diglycolamide (TODGA) as the extractant, tri-n‑butyl phosphate (TBP) as the phase modifier and 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl]pyridine (PyTri-Diol or PTD) as hydrophilic stripping agent. This 'hot test' was successfully carried out, achieving 99.92% removal of americium-241 (241Am) with a separation factor SF(Eu/Am) of 3.8 × 103 in the actinide(Ⅲ) product solution. The results show that bisamide podand extractants can effectively realize the extraction and separation of actinide(Ⅲ) and lanthanum(Ⅲ) from Chinese commercial HLLW and thus have a bright practical application potential for the treatment of commercial HLLW.
Internal contamination of actinides has led to significant health hazards to the public and workers in the context of nuclear power plant accidents, uranium ore mining, and reprocessing of the used fuel. An effective sequestering agent that is able to remove accidentally incorporated actinides in vivo with low toxicity is always in urgent need. The molecular decorporation ligands have been the most widely researched agents for the past few decades, while preliminary studies of functionalized nanoparticles have shown their clear advantages in metal binding selectivity, toxicity, and oxidative stress alleviation. Herein, the state-of-the-art of those two types of decorporation agents is presented with special attention being paid on the correlation between the solution and solid-state chemistry of those agents with actinides and the corresponding decorporation efficacies.
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