Thorium (Th) separation from acidic solutions is crucial for both resource recovery and environmental protection, while most materials suffer from limitations such as poor selectivity, slow kinetics, and insufficient acid and radiation tolerance. In this work, a pyrazine ethylamide-functionalized pillar[5]arene (P[5]A-PEA) was designed and employed as a highly preorganized N, O-hybrid ligand for selective Th(IV) coordination and separation. The complexation behaviors between P[5]A-PEA and Th(IV) were systematically investigated by virtue of multiple techniques including UV-vis titration, Job plot analysis, FT-IR spectroscopy, ESI-MS, EXAFS, and DFT calculations. The findings reveal that each P[5]A-PEA molecule binds to a Th(IV) ion with four functional chains through amide oxygen and pyrazine nitrogen atoms, forming a stable macrocyclic chelating complex. By impregnating P[5]A-PEA into a porous resin, the composite material achieves effective Th(IV) adsorption from acidic solution with efficiencies twice higher than those of the counterpart containing small molecules PA-PEA without P[5]A platform. The results highlight the significant role of pillar[5]arene skeleton in improving Th(IV) separation efficiency. In addition, the P[5]A-PEA-based material exhibits merits such as fast adsorption kinetics, high selectivity, excellent reusability, effective dynamic Th(IV) separation, and outstanding γ-irradiation resistance even at a dose of 1000 kGy. This work demonstrates a feasible approach to efficient Th(IV) separation from complicated water environments.
Six-nines (6N, ≥99.9999 wt%) tungsten powder is an indispensable material for next-generation semiconductors, microelectronics, and nuclear fusion devices, in which even trace impurities can severely undermine device performance, reliability, and lifetime. This paper systematically reviewed the state-of-the-art manufacturing routes for 6N tungsten powder, encompassing solvent extraction, multiple crystallization, zone refining, and chemical vapor deposition (CVD), with particular emphasis on the role of hydrometallurgical unit operations, especially solvent extraction and multiple crystallization of ammonium paratungstate (APT), in controlling impurity content and ensuring precursor purity. These hydrometallurgical operations determine the transfer and removal of trace impurities before downstream thermal conversion and reduction, and thus play a critical role in achieving the required chemical purity of the final tungsten powder. This paper critically evaluated various advanced characterization methodologies, especially glow discharge mass spectrometry (GDMS), alongside emerging analytical strategies. Three principal challenges were identified: the prohibitive cost and inherent metrological uncertainty of GDMS purity quantification exacerbated by the absence of matrix-matched certified reference materials (CRMs), the insufficiently understood trade-off between ultra-high chemical purity and fine particle size, and the substantial environmental and occupational safety hazards associated with the CVD route employing toxic WF6 precursor gas. Accordingly, several prospective mitigation strategies including the development of economically viable and metrologically traceable analytical calibration frameworks, dedicated mechanistic investigations into the co-optimization of purity and granulometry during powder synthesis, and the exploration of fluorine-free alternative precursors for sustainable vapor-phase synthesis, were proposed to guide the future development of greener, more efficient, and precisely controllable manufacturing technologies for 6N tungsten powder.
