Selective Separation of U(VI) from Pu(IV) by 2,9-Diamide-1,10-phenanthroline Ligands at High Acidity: Extraction and Coordination Chemistry.

During the PUREX process, the separation between U(VI) and Pu(IV) is achieved by reducing Pu(IV) to Pu(III), which is complicated and energy-consuming. To address this issue, we report here the first case of separation of U(VI) from Pu(IV) by o-phenanthroline diamide ligands under high acidity. Two new o-phenanthroline diamide ligands (1,10-phenanthroline-2,9-diyl)bis(indolin-1-ylmethanone) (L1) and (1,10-phenanthroline-2,9-diyl)bis((2-methylindolin-1-yl)methanone) (L2) were synthesized, which can effectively separate U(VI) from Pu(IV) even at 4 mol/L HNO3. The highest separation factor of U(VI) and Pu(IV) can reach over 1000, setting a new record for the separation of U(VI) from Pu(IV) under high acidity. Furthermore, extracted U(VI) can be easily recovered with water or dilute nitric acid, and the extraction performance remains stable even after 150 kGy gamma irradiation, which provides solid experimental support for potential engineering applications. The results of UV-vis titration and single-crystal X-ray diffraction measurements show that the 1:1 complex formed by L1 with U(VI) is more stable than all of the previously reported phenanthroline ligands, which reasonably reveals that the ligand L1 designed in this work has excellent affinity for U(VI). The findings of this work promise to contribute to the facilitation of the PUREX process by avoiding the use of reducing agents. It also provides new clues for designing ligands to achieve efficient separation between U(VI) and Pu(IV) at high acidity.

Sequential Water Sorption/Desorption of a Nonporous Adaptive Organic Ligand Bridged Coordination Polymer for Atmospheric Moisture Harvesting.

Moisture harvesters with favourable attributes such as easy synthetic availability and good processability as alternatives for atmospheric moisture harvesting (AWH) are desirable. This study reports a novel nonporous anionic coordination polymer (CP) of uranyl squarate with methyl viologen (MV2+ ) as charge balancing ions (named U-Squ-CP) which displays intriguing sequential water sorption/desorption behavior as the relative humidity (RH) changes gradually. The evaluation of AWH performance of U-Squ-CP shows that it can absorb water vapor under air atmosphere at a low RH of 20 % typical of the levels found in most dry regions of the world, and have good cycling durability, thus demonstrating the capability as a potential moisture harvester for AWH. To the authors' knowledge, this is the first report on non-porous organic ligand bridged CP materials for AWH. Moreover, a stepwise water-filling mechanism for the water sorption/desorption process is deciphered by comprehensive characterizations combining single-crystal diffraction, which provides a reasonable explanation for the special moisture harvesting behaviour of this non-porous crystalline material.

Theoretical Insights into the Selectivity of Hydrophilic Sulfonated and Phosphorylated Ligands to Am(III) and Eu(III) Ions.

The separation of lanthanides and actinides has attracted great attention in spent nuclear fuel reprocessing up to date. In addition, liquid-liquid extraction is a feasible and useful way to separate An(III) from Ln(III) based on their relative solubilities in two different immiscible liquids. The hydrophilic bipyridine- and phenanthroline-based nitrogen-chelating ligands show excellent performance in separation of Am(III) and Eu(III) as reported previously. To profoundly explore the separation mechanism, herein, we first of all designed four hydrophilic sulfonated and phosphorylated ligands L1, L2, L3, and L4 based on the bipyridine and phenanthroline backbones. In addition, we studied the structures of these ligands and their neutral complexes [ML(NO3)3] (M = Am, Eu) as well as the thermodynamic properties of complexing reactions through the scalar relativistic density functional theory. According to the changes of the Gibbs free energy for the back-extraction reactions, the phenanthroline-based ligands L2 and L4 have stronger complexing capacity for both Am(III) and Eu(III) ions while the phosphorylated ligand L3 with the bipyridine framework has the highest Am(III)/Eu(III) selectivity. In addition, the charge decomposition analysis revealed a higher degree of charge transfer from the ligand to Am(III), suggesting stronger donor-acceptor interactions in the Am(III) complexes. This study can provide theoretical insights into the separation of actinide(III)/lanthanide(III) using hydrophilic sulfonated and phosphorylated N-donor ligands.

Theoretical Insights into Phenanthroline-Based Ligands toward the Separation of Am(III)/Eu(III).

The bistriazinyl-phenanthroline representative ligand, BTPhen, shows excellent extraction and separation ability for trivalent actinides and lanthanides. Herein, we first designed three phenanthroline-based nitrogen-donor ligands (L1, L2, and L3), and then studied the structural and bonding properties as well as thermodynamic properties of the probable complexes, ML(NO3)3 (M = Am or Eu and L = L1, L2, or L3), using scalar relativistic density functional theory. Our charge decomposition analysis revealed an obviously higher charge transfer from the ligand to Am(III) compared with the Eu(III) case for the studied complexes. Spin density analysis further showed a more significant degree of Am-to-ligand spin delocalization and the corresponding spin polarization on the ligands. According to the thermodynamic analysis, ligand L3 has the strongest complexation capacity for both Am(III) and Eu(III) ions, while ligand L1 has the highest Am(III)/Eu(III) selectivity in binary octanol/water solutions. We expected that this work can provide valuable theoretical support for the design of effective ligands for actinide(III)/lanthanide(III) separation in high level liquid waste.

Hydrophilic Sulfonated 2,9-Diamide-1,10-phenanthroline Endowed with a Highly Effective Ligand for Separation of Americium(III) from Europium(III): Extraction, Spectroscopy, and Density Functional Theory Calculations.

The design and development of a water-soluble heterocyclic ligand are believed to be an alternative way for improving the separation efficiency of actinides from lanthanides. Herein, we designed and synthesized a novel hydrophilic multidentate ligand: disulfonated N,N'-diphenyl-2,9-diamide-1,10-phenanthroline (DS-Ph-DAPhen) with soft and hard donor atoms, as a masking agent in aqueous solutions for Am(III) separation. The combination of N,N,N',N'-tetraoctyldiglycolamide in kerosene and DS-Ph-DAPhen in aqueous phases could separate Am(III) from Eu(III) across a range of nitric acid concentrations with very high selectivity. The coordination behaviors of Eu(III) with DS-Ph-DAPhen in aqueous solutions were studied by UV-vis titration, electrospray ionization mass spectrometry, and Fourier transform infrared spectra. The results indicated that Eu(III) ions could form both 1:1 and 1:2 complexes with the DS-Ph-DAPhen ligand in aqueous solution. Density functional theory calculation suggests that there are more covalent characters for Am-N bonds than that for Eu-N bonds in the complexes, which supports the better selectivity of the DS-Ph-DAPhen ligand toward Am(III) over Eu(III). This work demonstrates a feasible alternative approach to separating trivalent actinides from lanthanides with high selectivity.

Strong Periodic Tendency of Trivalent Lanthanides Coordinated with a Phenanthroline-Based Ligand: Cascade Countercurrent Extraction, Spectroscopy, and Crystallography.

Phenanthroline-diamide ligands have been reported in the selective separation of actinides over Eu(III); on the contrary, relevant basic coordination chemistry studies are still limited, and extraction under actual application conditions is rarely involved. In this work, N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline [Et-Tol-DAPhen (L)] was applied to explore the coordination performance of lanthanides in simulative high-level liquid waste. For the first time, cascade countercurrent extraction was conducted with Et-Tol-DAPhen as the extractant, which reveals the periodic tendency of the extraction efficiency of lanthanides to decrease gradually as the atomic number increases. Comparison of elements with similar radii verifies the hypothesis that the increase in the atomic number leads to a decrease in the ionic radius, thus reducing the coordination and extraction capacity of ligands. Slope analysis, electrospray ionization mass spectrometry, and ultraviolet-visible titration results show that the ligand forms 1:1 and 1:2 complexes with lanthanides and the coordination ability follows the tendency of extraction efficiency, and the first crystal structures of Lns(III) with a phenanthroline-diamide ligand, i.e., [LaL(NO3)3(H2O)] and [LaL2(NO3)2][(NO3)], were obtained, which confirms the conclusions described above. This work promises to enhance our comprehension of the chemical properties of Lns(III) and offer new clues for the design and synthesis of novel separation ligands.

Selective Separation of Am(III)/Eu(III) by the QL-DAPhen Ligand under High Acidity: Extraction, Spectroscopy, and Theoretical Calculations.

Although 1,10-phenanthroline-based ligands have recently shown vast opportunities for the separation of trivalent actinides (Ans(III)) from lanthanides (Lns(III)), the optimization and design of the extractant structure based on the phenanthroline framework remain hotspots for further improving the separation. Following the strategy of hard and soft donor atom combination, for the first time, the quinoline group was attached to the 1,10-phenanthroline skeleton, giving a lipophilic ligand, 2,9-diacyl-bis((3,4-dihydroquinoline-1((2H)-yl)-1),10-phenanthroline (QL-DAPhen)), for Am(III)/Eu(III) separation. In the presence of sodium nitrate, the ligand can effectively extract Am(III) over Eu(III) in HNO3 solution, with the separation factor (SFAm/Eu) ranging from 29 to 44. The coordination chemistry of Eu(III) with QL-DAPhen was investigated by slope analysis, NMR titration, UV-vis titration, Fourier transform infrared spectroscopy, electrospray ionization-mass spectrometry, and theoretical calculations. The experimental results unanimously confirm that the ligand forms both 1:1 and 1:2 complexes with Eu(III), and the stability constants (log ß) of each of the two complexes were obtained. Density functional theory calculations show that the Am-N bonds have more covalent characteristics than the Eu-N bonds in the complexes, which reveals the reason why the ligand preferentially bonds with Am(III). Meanwhile, the thermodynamic analysis reveals that the 1:1 complex is more thermodynamically stable than the 1:2 complex. The findings of this work have laid a solid theoretical foundation for the application of phenanthroline-based ligands in the separation of An(III) from practical systems.

Actinide Separation Inspired by Self-Assembled Metal-Polyphenolic Nanocages.

The separation of actinides has a vital place in nuclear fuel reprocessing, recovery of radionuclides, and remediation of environmental contamination. Here we propose a new paradigm of nanocluster-based actinide separation, namely, nanoextraction, that can achieve efficient sequestration of uranium in an unprecedented form of giant coordination nanocages using a cone-shaped macrocyclic pyrogallol[4]arene as the extractant. The U24-based hexameric pyrogallol[4]arene nanocages with distinctive [U2(PG)2] binuclear units (PG = pyrogallol) that rapidly assembled in situ in monophasic solvent were identified by single-crystal X-ray diffraction, MALDI-TOF mass spectrometry, NMR spectroscopy, and small-angle X-ray and neutron scattering. Comprehensive biphasic extraction studies showed that this novel separation strategy has enticing advantages such as fast kinetics, high efficiency, and good selectivity over lanthanides, thereby demonstrating its potential for efficient separation of actinide ions.

Selective Separation and Coordination of Europium(III) and Americium(III) by Bisdiglycolamide Ligands: Solvent Extraction, Spectroscopy, and DFT Calculations.

Diglycolamide-based ligands have recently received increased attention due to their outstanding affinity for trivalent actinides and lanthanides. The structure optimization of the ligands, however, still remains a hot topic to achieve better extraction performance. In this work, we prepare and investigate three multidentate diglycolamide ligands for the selective separation of Eu(III) over Am(III) from a nitric acid solution to explore the effect on the extraction of alkyl groups on the nitrogen atoms in the center of the BisDGA ligands. The introduction of ethyl or isopropyl groups on the central nitrogen atoms greatly increased the distribution ratios of trivalent metal ions and enhanced the separation factor of Eu(III) over Am(III). The complexation behaviors of Eu(III) and Am(III) ions were studied by slope analyses, electrospray ionization mass spectrometry (ESI-MS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The results indicated that the trivalent metal ions were extracted as 1:2 and 1:3 complexes for all three BisDGA ligands during the extraction. Density functional theory (DFT) calculations verified the relevant experimental conclusion that the selectivity of THEE-BisDGA for Eu(III) is better than that for Am(III). The metal-DGA bonds in the ML3(NO3)3 complexes seem to be stronger than those in ML2(NO3)3 complexes.

Efficient Photocatalytic Reduction of Aqueous Perrhenate and Pertechnetate.

The pertechnetate anion (99TcO4-) is a long-lived radioactive species that is soluble in aqueous solution, in contrast to sparingly soluble 99TcO2. Results are reported for photocatalytic reduction and removal of perrhenate (ReO4-), a nonradioactive surrogate for 99TcO4-, using a TiO2 (P25) nanoparticle suspension in formic acid under UV-visible irradiation. Re(VII) removal up to 98% was achieved at pH = 3 under air or N2. The proposed mechanism is Re(VII)/Re(IV) reduction mediated by reducing radicals (·CO2-) from oxidation of formic acid, not direct reduction by photogenerated electrons of TiO2. Recycling results indicate that photocatalytic reduction of ReO4- exhibits excellent regeneration and high activity with >95% removal even after five cycles. 99Tc(VII) is more easily reduced than Re(VII) in the presence of NO3- with very slow redissolution of reduced 99Tc. This study presents a novel method for the removal of ReO4-/99TcO4- from aqueous solution, with potential application for deep geological disposal.

Supramolecular Host-Guest Inclusion for Distinguishing Cucurbit[7]uril-Based Pseudorotaxanes from Small-Molecule Ligands in Coordination Assembly with a Uranyl Center.

Although the capability of supramolecular pseudorotaxane/rotaxane systems as ligands for coordination with actinides has been identified by the on-going emerging of uranyl-organic polyrotaxane compounds, it is, however, still unknown how supramolecular inclusion affects the coordination assembly of the simple "axle" ligand with uranyl species. Herein, a semi-rigid organic dicarboxylate compound [BzBPCEt]Br2 (L1 ) is selected as a small-molecule "axle" ligand and the corresponding cucurbit[7]uril (CB7)-based [2]pseudorotaxane ligand, [BzBPCEt]Br2 @CB7 (L1 @CB7) has been also synthesized through CB7-based inclusion in this work. A detailed comparison between uranyl complexes from the "axle" ligand L1 and those from pseudorotaxane L1 @CB7 has been conducted, demonstrating the significant role of CB7-based inclusion in distinguishing supramolecular pseudorotaxane ligands from small-molecule dicarboxylates in uranyl coordination assembly. Notably, the impact of supramolecular inclusion on the "axle" linker in the system with cucurbituril macrocycles involved is established for the first time. Detailed structure decipherment suggests that the significant effect of CB7 is attributed to hydrothermal stabilization of the "axle" ligand or increased steric hindrance to the groups nearby originated from the bulky size of macrocyclic CB7.

Sequence Analysis and Comparison of the Key Genes of Domestic Live Attenuated Varicella Vaccine.

Objective To analyze the safety and consistency of domestic live attenuated varicella vaccines (LAVVs) at gene level.Methods The key genes (ORF38,ORF54,and ORF62) of LAVVs produced by four Chinese manufacturers were amplified by polymerase chain reaction (PCR) and sequenced.The sequencing results were compared with the sequences of Dumas,P-Oka,and V-Oka strains in GenBank and with the sequences of Varilrix (GSK) and Varivax (Merck).Results The ORF38 and ORF54 gene sequences of four domestic LAVVs were the same as each other and completely consistent with the sequences of V-Oka and Varilrix;however,it was different from Varivax (Merck) at one site.The ORF62 gene sequences of four domestic LAVVs were similar,and had individual nucleotide differences with V-Oka,Varilrix(GSK),and Varivax (Merck).Conclusions The sequences of ORF38,ORF54,and ORF62 of four domestic LAVVs are almost the same,showing good stability.They have small differences with V-Oka,Varilrix(GSK),and Varivax (Merck),without introducing new mutations.

An Unprecedented Two-Fold Nested Super-Polyrotaxane: Sulfate-Directed Hierarchical Polythreading Assembly of Uranyl Polyrotaxane Moieties.

The hierarchical assembly of well-organized submoieties could lead to more complicated superstructures with intriguing properties. We describe herein an unprecedented polyrotaxane polythreading framework containing a two-fold nested super-polyrotaxane substructure, which was synthesized through a uranyl-directed hierarchical polythreading assembly of one-dimensional polyrotaxane chains and two-dimensional polyrotaxane networks. This special assembly mode actually affords a new way of supramolecular chemistry instead of covalently linked bulky stoppers to construct stable interlocked rotaxane moieties. An investigation of the synthesis condition shows that sulfate can assume a vital role in mediating the formation of different uranyl species, especially the unique trinuclear uranyl moiety [(UO2 )3 O(OH)2 ](2+) , involving a notable bent [O=U=O] bond with a bond angle of 172.0(9)°. Detailed analysis of the coordination features, the thermal stability as well as a fluorescence, and electrochemical characterization demonstrate that the uniqueness of this super-polyrotaxane structure is mainly closely related to the trinuclear uranyl moiety, which is confirmed by quantum chemical calculations.

New insight of coordination and extraction of uranium(VI) with N-donating ligands in room temperature ionic liquids: N,N'-diethyl-N,N'-ditolyldipicolinamide as a case study.

Room temperature ionic liquids (RTILs) represent a recent new class of solvents applied in liquid/liquid extraction based nuclear fuel reprocessing, whereas the related coordination chemistry and detailed extraction processes are still not well understood and remain of deep fundamental interest. The work herein provides a new insight of coordination and extraction of uranium(VI) with N-donating ligands, e.g., N,N'-diethyl-N,N'-ditolyldipicolinamide (EtpTDPA), in commonly used RTILs. Exploration of the extraction mechanism, speciation analyses of the extracted U(VI), and crystallographic studies of the interactions of EtpTDPA with U(VI) were performed, including the first structurally characterized UO2(EtpTDPA)2(NTf2) and UO2(EtpTDPA)2(PF6)2 compounds and a first case of crystallographic differentiation between the extracted U(VI) complexes in RTILs and in molecular solvents. It was found that in RTILs two EtpTDPA molecules coordinate with one U(VI) ion through the carbonyl and pyridine nitrogen moieties, while NTf2(-) and PF6(-) act as counterions. The absence of NO3(-) in the complexes is coincident with a cation-exchange extraction. In contrast, both the extracted species and extraction mechanisms are greatly different in dichloromethane, in which UO2(2+) coordinates in a neutral complex form with one EtpTDPA molecule and two NO3(-) cations. In addition, the complex formation in RTILs is independent of the cation exchange since incorporating UO2(NO3)2, EtpTDPA, and LiNTf2 or KPF6 in a solution also produces the same complex as that in RTILs, revealing the important roles of weakly coordinating anions on the coordination chemistry between U(VI) and EtpTDPA. These findings suggest that cation-exchange extraction mode for ILs-based extraction system probably originates from the supply of weakly coordinating anions from RTILs. Thus the coordination of uranium(VI) with extractants as well as the cation-exchange extraction mode may be potentially changed by varying the counterions of uranyl or introducing extra anions.

Template-free synthesis and mechanistic study of porous three-dimensional hierarchical uranium-containing and uranium oxide microspheres.

A novel type of uranium-containing microspheres with an urchin-like hierarchical nano/microstructure has been successfully synthesized by a facile template-free hydrothermal method with uranyl nitrate hexahydrate, urea, and glycerol as the uranium source, precipitating agent, and shape-controlling agent, respectively. The as-synthesized microspheres were usually a few micrometers in size and porous inside, and their shells were composed of nanoscale rod-shaped crystals. The growth mechanism of the hydrothermal reaction was studied, revealing that temperature, ratios of reactants, solution pH, and reaction time were all critical for the growth. The mechanism study also revealed that an intermediate compound of 3 UO3 ⋅NH3 ⋅5 H2 O was first formed and then gradually converted into the final hydrothermal product. These uranium-containing microspheres were excellent precursors to synthesize porous uranium oxide microspheres. With a suitable calcination temperature, very uniform microspheres of uranium oxides (UO2+x , U3 O8 , and UO3 ) were successfully synthesized.

Excellent selectivity for actinides with a tetradentate 2,9-diamide-1,10-phenanthroline ligand in highly acidic solution: a hard-soft donor combined strategy.

In this work, we reported a phenanthroline-based tetradentate ligand with hard-soft donors combined in the same molecule, N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen), for the group separation of actinides over lanthanides. The synthesis and solvent extraction as well as complexation behaviors of the ligand with actinides and lanthanides are studied experimentally and theoretically. The ligand exhibits excellent extraction ability and high selectivity toward hexavalent, tetravalent, and trivalent actinides over lanthanides in highly acidic solution. The chemical stoichiometry of Th(IV) and U(VI) complexes with Et-Tol-DAPhen is determined to be 1:1 using X-ray crystallography. The stability constants of some typical actinide and lanthanide complexes of Et-Tol-DAPhen are also determined in methanol by UV-vis spectrometry. Density functional theory (DFT) calculations reveal that the An-N bonds of the Et-Tol-DAPhen complexes have more covalent characters than the corresponding Eu-N bonds, which may in turn lead to the selectivity of Et-Tol-DAPhen toward actinides. This ligand possesses merits of both alkylamide and 2,9-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-1,10-phenanthroline (R-BTPhen) extractants for efficient actinide extraction and the selectivity toward minor actinides over lanthanides and hence renders huge potential opportunities in high-level liquid waste (HLLW) partitioning.

Thermodynamic study on the complexation of Am(III) and Eu(III) with tetradentate nitrogen ligands: a probe of complex species and reactions in aqueous solution.

A thermodynamic investigation has been performed to study the complexation of trivalent metal (M) ions (M = Am(III), Eu(III)) with tetradentate ligands (L), 6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines (BTBPs), by using relativistic quantum mechanical calculations. The structures and stabilities of the inner-sphere BTBPs complexes were explored in the presence of various counterions such as NO(3)(-), Cl(-), and ClO(4)(-). According to our calculations, Am(III) and Eu(III) can chelate eight or nine water molecules at most, whereas more stable species like M(NO(3))(3)(H(2)O)(4) tend to be formed in the presence of nitrate ions. The inner sphere of the BTBPs complexes can accommodate four water molecules or three nitrate ions based on our calculations, forming species such as [ML(H(2)O)(4)](3+) and ML(NO(3))(3). Compared with Eu(III) complexes, the Am(III) counterparts have obviously lower binding energies in both the gas phase and solution. In addition, the solvent effect significantly decreases the binding energies of the BTBPs complexes. It has been found that the complexing reactions, in which products and reactants possess the same or close number of nitrate ions, are more favorable for formation of the BTBPs complexes. In short, the reactions of M(NO(3))(3)(H(2)O)(4) → ML(NO(3))(3) and [M(NO(3))(H(2)O)(7)](2+) → [ML(2)(NO(3))](2+) are probably the dominant ones in the Am(III)/Eu(III) separation process.

Controllable photomechanical bending of metal-organic rotaxane crystals facilitated by regioselective confined-space photodimerization.

Molecular machines based on mechanically-interlocked molecules (MIMs) such as (pseudo) rotaxanes or catenates are known for their molecular-level dynamics, but promoting macro-mechanical response of these molecular machines or related materials is still challenging. Herein, by employing macrocyclic cucurbit[8]uril (CB[8])-based pseudorotaxane with a pair of styrene-derived photoactive guest molecules as linking structs of uranyl node, we describe a metal-organic rotaxane compound, U-CB[8]-MPyVB, that is capable of delivering controllable macroscopic mechanical responses. Under light irradiation, the ladder-shape structural unit of metal-organic rotaxane chain in U-CB[8]-MPyVB undergoes a regioselective solid-state [2 + 2] photodimerization, and facilitates a photo-triggered single-crystal-to-single-crystal (SCSC) transformation, which even induces macroscopic photomechanical bending of individual rod-like bulk crystals. The fabrication of rotaxane-based crystalline materials with both photoresponsive microscopic and macroscopic dynamic behaviors in solid state can be promising photoactuator devices, and will have implications in emerging fields such as optomechanical microdevices and smart microrobotics.

Trivalent actinide and lanthanide separations by tetradentate nitrogen ligands: a quantum chemistry study.

Although a variety of tetradentate ligands, 6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines (BTBPs), have been proved as effective ligands for selective extraction of Am(III) over Eu(III) experimentally, the origin of their selectivity is still an open question. To elucidate this question, the geometric and electronic structures of the actinide and lanthanide complexes with the BTBPs have been investigated systematically by using relativistic quantum chemistry calculations. We show herein that in 1:1 (metal:ligand) type complexes substitution of electron-donating groups to the BTBP molecule can enhance its coordination ability and thus the energetic stability of the formed Am(III) and Eu(III) complexes in the gas phase. According to our results, Eu(III) can coordinate to the BTBPs with higher stability in energy than Am(III), no matter whether there are nitrate ions in the inner-sphere complexes. The presence of nitrate ions leads to formation of the probable Am(III) and Eu(III) complexes, M(NO(3))(3)(H(2)O)(n) (M = Am, Eu), in nitric acid solutions. It has been found that the changes of Gibbs free energy play an important role for Am(III)/Eu(III) separation. In fact, the weaker complexing ability of Am(III) with nitrate ions and water molecules makes the decomposition of Am(NO(3))(3)(H(2)O)(4) more favorable in energy, which may thus increase the possibility of formation of Am(BTBPs)(NO(3))(3). Our work may shed light on the design of novel extractants for Am(III)/Eu(III) separation.

In-situ anodic precipitation process for highly efficient separation of aluminum alloys.

Electrorefining process has been widely used to separate and purify metals, but it is limited by deposition potential of the metal itself. Here we report in-situ anodic precipitation (IAP), a modified electrorefining process, to purify aluminium from contaminants that are more reactive. During IAP, the target metals that are more cathodic than aluminium are oxidized at the anode and forced to precipitate out in a low oxidation state. This strategy is fundamentally based on different solubilities of target metal chlorides in the NaAlCl4 molten salt rather than deposition potential of metals. The results suggest that IAP is able to efficiently and simply separate components of aluminum alloys with fast kinetics and high recovery yields, and it is also a valuable synthetic approach for metal chlorides in low oxidation states.