Songdong Ding

A direct correlation between acid medium, ligand coordination, and Sc extraction is established, enabling predictive selection for red mud processing.

The performance of nitrilotriacetamide (denoted as NTAamide or L) in extracting and separating Am(III)/Eu(III) is strongly governed by the nitric acid concentration; however, the interaction mechanism connecting acidity to extractability remains unclear. Herein, five types of representative NTAamide-extracted Am(III)/Eu(III) species were comprehensively examined by density functional theory calculations and ab initio molecular dynamics simulations. The extracted complexes were classified as ligand-neutral M-L (M:L = 1:1, 1:2, and 2:2) and ligand-protonated M-HL (M:HL = 1:1 and 1:2), with one to three HNO3 molecules explicitly included to simulate the nitric acid media. With increasing acidity, most extracted complexes prefer forming thermodynamically less stable species, corroborated by electronic structure analyses. Specifically, structural optimizations and dynamic simulations find acidity-weakened metal–oxygen coordination in the 1:1 M-L complex, decreasing the inner-sphere coordination number from nine to eight; in contrast, the rest of the species mainly reorganize and weaken outer-sphere noncovalent interactions. Meanwhile, high acidity promotes NTAamide protonation, and the produced M-HL complexes are less stable on average than the M-L species. It is evident that the former ones have more positive total bond interaction energies (e.g., weaker bonding strength) and less thermodynamic stability. Thus, the established acidity–extractability correlation rationalizes experimental findings and guides amide extractant design for selective lanthanide/actinide separation.

Understanding the extraction and stripping behavior of UO₂²⁺ and Th⁴⁺ with α-irradiated extractants is critical for their applications in spent nuclear fuel (SNF) reprocessing. In this work, the effect of external α-radiolysis on the extraction and stripping of UO₂²⁺ and Th⁴⁺ by the TiAP extraction system was investigated via experimental and theoretical approaches. Experiments indicated that α-radiolysis enhanced the extraction of UO₂²⁺ and Th⁴⁺ but suppressed their stripping. Mass spectrometry (MS) and molecular dynamics (MD) simulations demonstrated that strong electrostatic interactions between the representative α-radiolysis products, di-iso-amyl phosphate (DiAP^-) and tri-iso-pentyl pyrophosphate (TriPP^-), and the metal ions led to the formation of UO₂(DiAP/TriPP)₂(TiAP)₂ and Th(DiAP/TriPP)₄(TiAP) complexes, thereby enhancing extraction. Furthermore, the adsorption of stable UO₂(DiAP/TriPP)₂(H₂O)₃ and Th(DiAP/TriPP)₄(H₂O)₅ complexes at the liquid-liquid interface hindered stripping and may promote third-phase formation. Moreover, the minor acidic pyrophosphate ester compounds were found to be more detrimental to the TiAP extractant system. This work elucidates the effects of α-radiolysis on UO₂²⁺ and Th⁴⁺ extraction in the 36% TiAP-nDD/HOK-HNO₃ system, providing crucial insights for the subsequent application of TiAP in SNF reprocessing.

With the rapid development of nuclear energy, achieving efficient and highly selective separation of TcO₄^- from acidic nuclear wastewater has become an urgent challenge. In this context, three amine-triamide ligands were selected to investigate the effect of ligand structure on the extraction performance toward TcO₄^-/ReO₄^-. Among them, the short-chain ethyl-substituted ligand N,N-diethyl-N',N',N″,N″-tetraoctylnitrilotriacetamide (L_I) exhibited superior extractability and selectivity for TcO₄^-/ReO₄^- anions in dilute nitric acid solution compared to the long-chain butyl-substituted (L_II) and octyl-substituted (L_III), using n-dodecane as the diluent. The study of the relationship between ligand structure and extraction performance revealed that the overall extraction performance of amine-triamide ligands─including loading capacity, extraction efficiency, and selectivity─is governed by a combination of steric hindrance and lipophilicity. Remarkably, even at a NO₃^-/ReO₄^- molar ratio as high as 1000:1, ligand L_I maintained a D_Re value of 3.5 with negligible coextraction of coexisting cations, outperforming most functional adsorbents reported to date. Slope analysis and loading capacity tests indicated the formation of a 1:1 extracted complex between the amine-triamide ligand and TcO₄^-/ReO₄^-. Furthermore, characterization by electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) confirmed that the extraction proceeds via an anion-exchange mechanism.

Amine–diamides have exhibited good extractability toward radiotoxic pertechnetate (⁹⁹TcO₄^–) and high acidic resistance. Their starting cationic materials, however, have not been experimentally captured in the nitric acid media, and the enhanced extraction mechanism over triamide analogues remains underexplored. Herein, a series of 2,2′-(alkylimino)bis(N,N-diethylacetamide), marked as ^RNDA (R = Me, Et, n-Bu and n-Oct), for extracting TcO₄^– have been investigated using molecular dynamics and density functional theory calculations. The dynamically formed [(H^MeNDA)⁺·NO₃^–] was trapped for the first time, along with its anion exchange reaction with TcO₄^–. A binary extracted complex [(H^RNDA)⁺·TcO₄^–] was recognized and stabilized through multiple hydrogen bonds. It contrasts with the ternary complex of N,N,N′,N′,N′′,N′′-hexaethylnitrotriacetamide (NTA) that contains an additional water molecule. The difference is because more hydrophobic ^RNDA, especially with a long-chain alkyl substituent, squeezes the water out. It is found that ^RNDA shows better extractability than NTA. It is the alkyl introduction that has increased electron density around the central N atom (i.e., raised nucleophilicity and basicity) and concurrently decreased electron density of surrounding carbonic H atoms (raised electrophilicity and acidity). Taken together, the hydrogen-bonding interactions between NDA and TcO₄^– are enhanced.

Background: ⁶⁸ Ga is a key radionuclide in PET due to its favorable decay properties, generator availability, and growing preclinical and clinical use of ⁶⁸ Ga-labeled radiopharmaceuticals. The performance of the ⁶⁸ Ge/ ⁶⁸ Ga generator is critical for efficient ⁶⁸ Ga utilization. Here, a novel modified TiO ₂ -based ⁶⁸ Ge/ ⁶⁸ Ga generator ( ⁶⁸ Ge activity: 3.26 GBq) was evaluated for long-term performance, including ⁶⁸ Ga elution yield, ⁶⁸ Ge breakthrough, and metal impurities (Ti, Fe and Zn), and was verified in radiolabeling applications. Results: Over a two-year period, this generator maintained an average ⁶⁸ Ga elution yield of 79.8 ± 3.2% ( n = 209, range: 70.8%–87.1%), an average ⁶⁸ Ge breakthrough as low as 0.00003% ( n = 149, range: 0.0000035%–0.00031%), and Ti, Fe, and Zn concentrations well below the limit of 10 µg/GBq. The generator demonstrated compatibility with various precursors such as DOTA-TATE, Pentixafor and FAP-2286. Conclusion: The enhancement of the ⁶⁸ Ge(IV) loading capacity in the ⁶⁸ Ge/ ⁶⁸ Ga generator, along with improved ⁶⁸ Ga elution efficiency, facilitates the rapid and efficient production of ⁶⁸ Ga. This advancement contributes to the promotion and widespread adoption of ⁶⁸ Ga-based radiopharmaceuticals and benefits more patients. Graphical

The efficient separation of thorium (Th) from uranium (U) and rare earth elements (REEs) is crucial for the Th-based nuclear energy. To address the coextraction limitation of light REEs by NTAamide(n-Oct), two novel tetraamide derivatives of EDTA─EDTAamide(n-Bu) and EDTAamide(n-Oct)─were synthesized and characterized. Their extraction behaviors toward Th⁴⁺, UO₂²⁺, and RE³⁺ in HNO₃ media were systematically investigated. The extraction performance of both ligands decreased monotonically with increasing acidity. Both ligands achieved exceptional Th/RE separation, with separation factor (SF_Th/RE) ranging from 64 to 8.3 × 10² at 0.50-2.0 mol/L HNO₃. Notably, EDTAamide(n-Bu) exhibited superior Th/U selectivity (SF_Th/U = 78-1.3 × 10²) over EDTAamide(n-Oct) (SF_Th/U = 14-25), with optimal performance at 1.0 mol/L HNO₃. A 1:1 Th⁴⁺-EDTAamide(n-Bu) complex was confirmed, where the ligand coordinates as a hexadentate chelate via two central N atoms and four amide O atoms, forming a deca-coordinate Th⁴⁺ center with four inner-sphere H₂O molecules. The extraction process follows a spontaneous and endothermic neutral complexation mechanism, accompanied by an entropy increase. In a simulated monazite leachate, EDTAamide(n-Bu) achieved 98.1% Th⁴⁺ recovery with high selectivity, underscoring its strong potential for practical application.

Lanthanide/actinide (Ln/An) separation is a critical step in the reprocessing of spent nuclear fuels, enabling a more efficient utilization of nuclear resources and reducing nuclear waste contamination. However, separating Ln/An ions remains a significant challenge due to the similarity in their physicochemical properties. The periodic table and periodic law offer powerful tools for guiding chemical research. As Ln/An nuclides fall within the periodic trends, this provides possibilities for the optimized design of selective extractants. In this study, we systematically investigated the periodic patterns through which nitrilotriacetamide (NTAamide) selectively separates actinide-lanthanide ion pairs. The results indicate that separating ion pairs within the same group follows the Difference Model, while separating ion pairs of the same period follows the Similarity Model. Furthermore, our modified extractants exhibited enhanced separation selectivity for Ln/An ion pairs from the same group or period, which was validated by retrosynthetic analysis based on machine learning models. Detailed computational characterizations reveal that the modulation of the metal-oxygen bond strength is the microscopic origin underlying the enhanced separation performance.