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Effectively addressing global warming requires a rapid transformation of the ways in which energy is consumed, and nuclear power produces very low lifecycle carbon emissions. Efficient uranium extraction from unconventional uranium ore sources, such as the ocean, can provide a stable and long-term supply of nuclear fuel for nuclear power plants. Herein, we report an interconnected open-pore architecture poly(amidoxime) (PAO) fiber with PAO nanoparticles and a nano-channel structure (AO-OpNpNc) using a top-down design. A high uranium adsorption capacity of 17.57 mg-U per g-adsorbent in natural seawater and ultra-long service life of at least 30 cycles were obtained, which are the highest values among currently available adsorbents to our knowledge. Extended X-ray absorption fine structure (EXAFS) fits and density functional theory (DFT) computational studies suggest that PAO-bound uranyl is a cooperative chelating model. More importantly, uranium production costs could be reduced to $80.70–86.25 per kg of uranium with this fiber, which is similar to the uranium spot price of $86.68 per kg of uranium and lower than the costs of all currently available adsorbents. The exceptional durability of the AO-OpNpNc fibers suggests the possibility of economically producing nuclear fuel from the ocean.

The development of amidoxime-based polymeric (ABP) fibers offers a solution for uranium extraction from seawater (UES) and provides an alternative solution to the uranium resource shortage. However, ABP adsorbents prepared by existing methods cannot meet the requirements of high adsorption capacity, high selectivity, good mechanical strength and long service life. Herein, we fabricated a 3D hierarchical porous, high specific surface area ABP (H-ABP) fiber via self-assembly of axial grafting chains. A high adsorption capacity of 11.50 mg-U per g-adsorbents was achieved in natural seawater, which is a significant breakthrough in UES. Meanwhile, the adsorption capacity of uranium was higher than its major competing element vanadium, which overturned the U/V mass ratio of the ABP fiber. The H-ABP fiber also exhibited good mechanical strength and a long service life of at least 10 adsorption–desorption cycles. The well-designed structure resulted in groundbreaking properties, which completely meet the requirements for the economic evaluation of UES. This work presents a new technology for the synthesis of highly efficient adsorbents for UES, thus opening a whole new means of nuclear fuel production from the ocean.

A unique selective crystallization strategy based on an iodate-sulfate mixed-anion system has been developed for lanthanide separation. Periodic divergences in crystal formation energy enable simple Nd/Dy, La/Lu, Gd/Tb, La/Dy, and Nd/Lu separations through crystallization of the early lanthanides, giving rise to separation factors up to 123(5), 100(2), 2.4(2), 137(9), and 85(6), respectively.

The reduction mechanism of Pt(4+) ions confined in the channel of multi-walled carbon nanotubes was mainly investigated using X-ray absorption fine structure (XAFS) spectroscopy, with the aid of TEM, Raman, XRD and ICP-AES studies. The XAFS spectra revealed the spontaneous formation of Pt nanoparticles when H2PtCl6 was confined in multi-walled carbon nanotubes (MWCNTs). The Pt L3-edge X-ray absorption near edge structure (XANES) coupled with the C K-edge NEXAFS results indicated that the reduction of Pt(4+) from tetravalent to zerovalent was attributed to the electron transfer from MWCNTs. The Fourier transform R-space of the Pt L3-edge XAFS data displayed that the nanoconfinement effect of MWCNTs promoted the formation of Pt nanoparticles. Moreover, the Pt-Pt bond length in confined Pt nanoparticles became shorter than that of Pt in the bulk state. Furthermore, by varying the inner diameter of MWCNTs from 15 nm to 10 nm and 5 nm, the Pt-Pt bond length of nanoconfined Pt nanoparticles decreased gradually. The results clearly revealed that MWCNTs acting as enriched electron donors can continuously reduce the confined Pt ions to Pt nanoparticles, thereby showing a great potential for the design of a new type of confined nanocatalysts.

The physicochemical properties of large molecules confined in nanopores are expected to be different from those of the bulk. This study investigates the cation–anion relative position and the molecular orientation of the 1-hexyl-3-methylimidazolium bromide (C6mimBr) ionic liquid intercalated in LAPONITE® by a temperature-dependent X-ray absorption fine structure (XAFS) and some traditional methods (TEM, DSC, XRD, and IR). DSC and TEM analyses revealed the formation of C6mimBr crystals intercalated in LAPONITE®. The XAFS and XRD analyses at ambient temperature revealed that an ordered monolayer structure, with C6mim+ cations intercalated in the interlayer nanospace and Br located on the edge of the LAPONITE®, was formed when ILs were intercalated in LAPONITE®. The results also demonstrated that the enhanced interactions, the formed hydrogen bonds, as well as the ordered monolayer arrangement induced the formation of C6mimBr crystals when intercalated in LAPONITE®. In situ XAFS analysis with a combination of XRD patterns at varied temperatures revealed that the structure orientation of the intercalated C6mim+ cations tends to deflect and maintain the ordered monolayer arrangement with the elevation of temperature. The ordered crystal structure still exists at 120 °C and disappears at a higher temperature.

The polystyrene-supported primary amine -CH2NH2 has shown an at least 3-fold increase in uranyl capacity compared to a diamidoxime ligand on a polystyrene support. This study aims to understand the coordination of substitution complexes from UO2(CO3)3(4-) and amines using density functional theory calculations. Four kinds of amines (diethylamine (DEA), ethylenediamine (EDA), diethylenetriamine (DETA) and triethylenetetramine (TETA)) were selected because they belong to different classes and have different chain lengths. The geometrical structures, electronic structures and the thermodynamic stabilities of various substitution complexes, as well as the trends in their calculated properties were investigated at equilibrium. In these optimized complexes, DEA groups bind to uranyl as monodentate ligands; EDA groups serve as monodentate and bidentate ligands; DETA groups act as monodentate and tridentate ligands; while TETA groups serve as monodentate, bidentate and tridentate ligands. The thermodynamic analysis confirmed that the primary amines coordinate to uranyl more strongly than does the secondary amine. The stabilities of substitution complexes with primary amines were calculated to decrease with increasing chain length of the amine, except for UO2(L2)(2+). Of the complexes analyzed, only UO2L(CO3)2(2-) (L = EDA and DETA) and UO2L2CO3 (L = EDA) were predicted to form from the substitution reactions with UO2(CO3)3(4-) and protonated amines as reactants in aqueous solution. Amines were calculated to be comparable to, or sometimes weaker than, amidoximate in replacing CO3(2-) in UO2(CO3)3(4-) to coordinate to uranium. Therefore, the coordination mechanism, in which amines replace carbonates to bind to uranyl, is not primarily responsible for the experimentally observed 3-fold or greater increase in uranyl capacity of primary amines compared to a diamidoxime ligand. Based on the results of our calculations, we believe that the cation exchange mechanism, in which the protonated amines bind to uranyl tricarbonate directly, plays a leading role in the uranium recovery from seawater by amines.

[Emim]Br ionic liquid was confined in porous SiO2 nanoparticles. It is shown that the confinement in the nanopores leads to a compression of molecular size and an increase in the melting point. The pore size of SiO2 is a key factor in tuning the anion-cation distance and the melting point of the confined ionic liquids.

By means of density functional theory (DFT) calculations, we study the water adsorption behavior on two common surfaces, (001) and (100) TiO(2)-B, which maintains the monoclinic structure as high as approximately 550 degrees C or higher in ambient conditions. The two surfaces show totally different activity for water dissociation. The dissociative chemisorption of water on TiO(2)-B (100) is identified at both submonolayer and monolayer coverages, which indicates considerable reactivity. In contrast, the non-dissociative molecular adsorption of water is the most stable state on TiO(2)-B (001) which suggests no special activity. Furthermore, we compare the structural features of different surfaces with diverse crystal structures, such as rutile, anatase, brookite, TiO(2)-B etc. Keeping a close eye on the exposed atoms on the surface, we conclude a more general criterion for a quick evaluation of reactivities of different TiO(2) surfaces merely based on local surface structure features.