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Abstract: Novel crystalline actinide materials can be used to immobilize uranium and transuranium elements at radioactive waste disposal sites. However, the stability and dissolution of such phases are still poorly understood. In this study, we investigated the dissolution kinetics of two uranyl borates and one plutonyl borate, UO2B2O4 (UBO), Na[(UO2)B6O10(OH)]·2H2O (NaUBO), and PuO2[B8O11(OH)4] (PuBO), with three different ligands, i.e., bicarbonate, phosphate, and natural humic acid (HA). These actinide borates were chosen because they possess different topologies that may influence dissolution. In the presence of bicarbonate, the apparent steady-state concentration of dissolved U(VI) and surface area-normalized dissolution rates were much higher for UBO compared to NaUBO. Uranyl phosphate, most likely in the form of (UO2)3(PO4)2(H2O)4, was precipitated on the surface of residual particles of UBO and NaUBO with phosphate. The dissolution rate of PuBO in NaNO3 solution was much higher than UBO or NaUBO. This study revealed that actinide borate crystal dissolution was substantially influenced by crystalline structures of actinide borates and aqueous ligands. [Copyright &y& Elsevier]

Bis(2-propyloxy)calix[4]arene-crown-6 ( L1 ) is a ligand with high affinity in the extraction of Cs(I). In this work, acrylamido and propionamido groups are decorated at the opposite site of 2-propyloxy on the phenyl ring of L1 , giving rise to the derivatives L2 and L3 , respectively. Complexation of all the three ligands with Cs(I) is characterized by NMR, spectrophotometric titration, crystal structure and DFT calculation. Both the NMR and spectrophotometric analysis suggest more significant variation of electron density on the phenyl rings in L2 and L3 than that in L1 in complexation with Cs(I). The stability constants (log β ) of the complexes are calculated to be 6.0 ± 0.1, 6.2 ± 0.1 and 6.3 ± 0.1 for Cs- L1 , Cs- L2 and Cs- L3 , respectively, by fitting of the absorption spectra. As reflected by the crystal structures and DFT calculations, the complexed cesium cation interacts with the crown ether moiety, the two rotated phenyl rings and the acrylamido/propionamido groups in L2 / L3 , which can be regarded as an intramolecular triple cooperative effect. Extraction of Cs(I) from aqueous solution is performed, and the distribution ratio is in line with the findings in stability constant and interaction energy. This work contributes to further improvement of the extraction of cesium cation by 1,3-alternate calix[4]arene-crown-6. [ABSTRACT FROM AUTHOR]

Bis(trifluoromethylsulfonyl)imide (NTf 2 − ) and hexafluorophosphate (PF 6 − ) are the most frequently used anions for hydrophobic ionic liquids (ILs) which have been considered as promising solvents in the extraction of cesium ions. The interactions of NTf 2 − and PF 6 − with Cs + were explored in this work. The results of DFT calculation indicated that both Cs + and Cs(18C6) + prefer to interact with two NTf 2 − or PF 6 − anions in gas phase, where 18C6 is 18-crown-6. The complex of Cs(NTf 2 ) 2 − was observed in electrospray ionization mass spectrometry (ESI-MS), and the complexes of [Cs(18C6)NTf 2 ] 2 and [Cs(18C6)PF 6 ] 2 were crystallized in which Cs(18C6) + interacted with two anions. The interactions of NTf 2 − with cesium resulted in a synergistic effect between dicyclohexano-18-crown-6 (DCH18C6) and NTf 2 − in the extraction of Cs + using n -octanol as diluent. However, DFT calculation revealed that the complex Cs(DCH18C6) + interacted with one NTf 2 − anion was more thermodynamically stable than that with two anions in organic phase, different from that in gas phase. [ABSTRACT FROM AUTHOR]

Under hydrothermal condition, the decomposition of methanesulfonic acid to sulfate anion is observed, resulting in the formation of a novel thorium sulfate fluoride compound ThF 2 (SO 4 )(H 2 O) ( 1 ). This complex is structurally characterized by single crystal X-ray diffraction, revealing a three-dimensional structure crystallized in the monoclinic space-group P 2 1 / n , where thorium cation is nine coordinated by four SO 4 2− oxygen atoms, four bridging F − , and one H 2 O molecule. The crystal lattice parameters are a = 6.9065(7) Å, b = 6.9256(7) Å, c = 10.5892(11) Å, β = 96.755(2)°, V = 502.98(9) Å 3 , Z = 4. The temperature dependent UV–Vis–NIR absorption spectra and fluorescence spectra were collected from 77 K to 300 K, where the intensities of the peaks varied as a function of temperature. The Raman vibrational spectrum of the samples collected from 100 to 2000 cm −1 shows identical SO 4 2− vibration modes. [ABSTRACT FROM AUTHOR]

Two new uranyl phosphonates were synthesized by using p -xylenediphosphonic acid ( pmb H 4 ) to react with uranyl salts in Emim or BMMim ([EMim][PF 6 ] = 1-ethyl-3-methylimidazolium hexafluorophosphate; [BMMim]Cl = 1-butyl-2,3-dimethylimidazolium chloride) at elevated temperature, namely [EMim][UO 2 ( pmb H 2 ) 0.5 ( pmb H 2 ) 0.5 (ox) 0.5 ] ( 1 ) and [BMMim] 2 [(UO 2 ) 2 (pmb H 2 )( pmb )] ( 2 ). Both compounds adopt two dimensional structures, consisting of an anionic layer of uranyl phosphonate, with cations filled in the interlayer spaces. The spectroscopic properties of the compounds were studied extensively using UV–Vis absorption, temperature dependent fluorescence, Raman and IR spectroscopies. The UV–Vis absorption spectrum contains typical peaks of uranyl complexes at around 320 nm and 420 nm, which are originated from the charge transfer transitions from O 2p orbitals to the U 5f/6d orbitals. Both compounds adopt five strong emission peaks, whose intensities increase with the decrease of temperature, as observed in the temperature dependent fluorescence spectra. In Raman and IR spectra, the peaks corresponding to the stretch of C–H/O–H, P–O/P O, and O U O bonds could all be located and assigned. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZJU-X6 is a 3-fold interlocking cationic MOF and could capture 99TcO 4. • ZJU-X6 exhibited superior sorption ability and reusability toward 99TcO 4. • PDF and crystal structure clearly elucidated the sorption mechanism. Technetium-99 is one of most problematic radionuclides with a long half-life, high environmental mobility and solubility, which exists mainly in the form of anionic pertechnetate (99TcO 4 -). Searching for sorbents that hold efficient and selective elimination of radioactive 99TcO 4 - from aqueous solution is still a big challenge and further visualizing it in the sorbents is extremely difficult. Herein, we utilized an elongated organic neutral pyridyl ligand linked with Ni2+ to yield a novel 3-fold interlocking cationic metal–organic framework (ZJU-X6). Unexpectedly, the structure of ZJU-X6 held unique displaceable water pairs on the Ni2+ node in comparison to cationic metal–organic framework constructed by Ni2+. Attainable Ni2+ nodes distinctly improved the positive charge density of the framework, affording high sorption capacity, excellent selectivity, and removal depth toward 99TcO 4 -. Pair distribution functions (PDF) were applied to analyze the changes of atom distances in materials before and after capturing ReO 4 -, clearly showing that ReO 4 - entered into the body of ZJU-X6. More detailed sorption mechanism was atomically elucidated by obtaining the single crystal structure of 99TcO 4 --incorporated ZJU-X6. It is found that the water pairs were replaced by 99TcO 4 - and each Ni2+ coordinated with two 99TcO 4 - through oxygen atoms. In addition, each 99TcO 4 - engaged in multiple C–H...O hydrogen bonding with H atoms of aromatic rings that enhanced the trapping of 99TcO 4 -. [ABSTRACT FROM AUTHOR]