Co-reporter:Zi-Jie Li, Zhi-Wei Huang, Wen-Lu Guo, Lin Wang, Li-Rong Zheng, Zhi-Fang Chai, and Wei-Qun Shi
Environmental Science & Technology May 16, 2017 Volume 51(Issue 10) pp:5666-5666
Publication Date(Web):April 14, 2017
DOI:10.1021/acs.est.6b05313
The separation and recovery of uranium from radioactive wastewater is important from the standpoints of environmental protection and uranium reuse. In the present work, magnetically collectable TiO2/Fe3O4 and its graphene composites were fabricated and utilized for the photocatalytical removal of U(VI) from aqueous solutions. It was found that, under ultraviolet (UV) irradiation, the photoreactivity of TiO2/Fe3O4 for the reduction of U(VI) was 19.3 times higher than that of pure TiO2, which is strongly correlated with the Fe0 and additional Fe(II) generated from the reduction of Fe3O4 by TiO2 photoelectrons. The effects of initial uranium concentration, solution pH, ionic strength, the composition of wastewater, and organic pollutants on the U(VI) removal by TiO2/Fe3O4 were systematically investigated. The results demonstrated its excellent performance in the cleanup of uranium contamination. As graphene can efficiently attract the TiO2 photoelectrons and thus decrease their transfer to Fe3O4, the photodissolution of Fe3O4 in the TiO2/graphene/Fe3O4 composite can be largely alleviated compared to that of the TiO2/Fe3O4, rendering this ternary composite a much higher stability. In addition, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES), and X-ray photoelectron spectroscopy (XPS) were used to explore the reaction mechanisms.
Co-reporter:Zhen-ni Xie, Lei Mei, Kong-qiu Hu, Liang-shu Xia, Zhi-fang Chai, and Wei-qun Shi
Inorganic Chemistry March 20, 2017 Volume 56(Issue 6) pp:3227-3227
Publication Date(Web):March 8, 2017
DOI:10.1021/acs.inorgchem.6b02515
A mixed-ligand system provides an alternative route to tune the structures and properties of metal–organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on C6BPCA@CB6 (C6BPCA = 1,1′-(hexane-1,6-diyl)bis(4-(carbonyl)pyridin-1-ium), CB6 = cucurbit[6]uril) ligand, UPS1 (UO2(L)0.5(SO4)(H2O)·2H2O, L = C6BPCA@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl polyrotaxane sheet structure of UPS1 is based on uranyl-sulfate ribbons connected by the C6BPCA@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl polyrotaxane compounds, UPO1–UPO4, have been acquired by tuning reaction pH and ligand concentration: UPO1 (UO2(L)0.5(C2O4)0.5(NO3)·3H2O) in one-dimensional chain was obtained at a low pH value range (1.47–1.89) and UPO2 (UO2(L)(C2O4)(H2O)·7H2O)obtained at a higher pH value range (4.31–7.21). By lowering the amount of oxalate, another two uranyl polyrotaxane network UPO3 ((UO2)2(L)0.5(C2O4)2(H2O)) and UPO4 ((UO2)2O(OH)(L)0.5(C2O4)0.5(H2O)) could be acquired at a low pH value of 1.98 and a higher pH value over 6, respectively. The UPO1–UPO4 compounds, which display structural diversity via pH-dependent competitive effect of oxalate, represent the first series of mixed-ligand uranyl polyrotaxanes with organic ligand as the coligand. Moreover, the self-assembly process and its internal mechanism concerning pH-dependent competitive effect and other related factors such as concentration of the reagents and coordination behaviors of the coligands were discussed in detail.
Co-reporter:Lei Mei, Cong-zhi Wang, Liu-zheng Zhu, Zeng-qiang Gao, Zhi-fang Chai, John K. Gibson, and Wei-qun Shi
Inorganic Chemistry July 17, 2017 Volume 56(Issue 14) pp:7694-7694
Publication Date(Web):June 23, 2017
DOI:10.1021/acs.inorgchem.7b00312
The reaction of uranyl nitrate with terephthalic acid (H2TP) under hydrothermal conditions in the presence of an organic base, 1,3-(4,4′-bispyridyl)propane (BPP) or 4,4′-bipyridine (BPY), provided four uranyl terephthalate compounds with different entangled structures by a pH-tuning method. [UO2(TP)1.5](H2BPP)0.5·2H2O (1) obtained in a relatively acidic solution (final aqueous pH, 4.28) crystallizes in the form of a noninterpenetrated honeycomb-like two-dimensional network structure. An elevation of the solution pH (final pH, 5.21) promotes the formation of a dimeric uranyl-mediated polycatenated framework, [(UO2)2(μ-OH)2(TP)2]2(H2BPP)2·4.5H2O (2). Another new polycatenated framework with a monomeric uranyl unit, [(UO2)2(TP)3](H2BPP) (3), begins to emerge as a minor accompanying product of 2 when the pH is increased up to 6.61, and turns out to be a significant product at pH 7.00. When more rigid but small-size BPY molecules replace BPP molecules, [UO2(TP)1.5](H2BPP)0.5 (4) with a polycatenated framework similar to 3 was obtained in a relatively acidic solution (final pH, 4.81). The successful preparation of 2–4 represents the first report of uranyl–organic polycatenated frameworks derived from a simple H2TP linker. A direct comparison between these polycatenated frameworks and previously reported uranyl terephthalate compounds suggests that the template and cavity-filling effects of organic bases (such as BPP or BPY), in combination with specific hydrothermal conditions, promote the formation of uranyl terephthalate polycatenated frameworks.
Co-reporter:Kui Liu;Ya-Lan Liu;Jing-Wen Pang;Li-Yong Yuan;Lin Wang
Science China Chemistry 2017 Volume 60( Issue 2) pp:264-274
Publication Date(Web):2017 February
DOI:10.1007/s11426-016-0321-x
This work presents a comprehensive study for the electrochemical behaviors of zirconium in LiCl-KCl eutectic. The effects of stirring, temperature and Zr concentration on the electrode reactions, the ZrCl4 sublimation from the melt, microcosmic morphologies of Zr deposits (ZrCl and Zr) obtained at different potential and temperature have been investigated. The behaviors of Zr(IV), on a large concentration range from 0.13% to 2.28% in melt, show a multiple-step reaction involving Zr(IV), Zr(II), ZrCl and Zr species. Temperature plays a crucial role on the changes of Zr(IV) reduction behavior on the solid electrode. The Zr(IV)/ZrCl couple is more easily observed at lower temperature and gradually diminishes with the increase of temperature. The Zr(IV)/Zr(II) and Zr(II)/Zr reactions are predominant on the W electrode at higher temperatures. At 673 K, a layered structure of insoluble ZrCl formed by potentiostatic electrolyses at 1.1 V was visualized by scanning electron microscopy-energy dispersive X-ray (SEM-EDS), while only Zr metal particles was observed at higher temperature than 773 K. An evolution of the Zr-based structure and size corresponding to the ZrCl and Zr metal based on different potentiostatic electrolysis was observed. The average particle size of the Zr metalparticles increases with the increase of temperature.
Co-reporter:Li-Yong Yuan, Lin Zhu, Cheng-Liang Xiao, Qun-Yan Wu, Nan Zhang, Ji-Pan Yu, Zhi-Fang Chai, and Wei-Qun Shi
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 4) pp:
Publication Date(Web):January 9, 2017
DOI:10.1021/acsami.6b15642
A preorganized tetradentate phenanthrolineamide (DAPhen) ligand with hard and soft donors combined in the same molecule has been found to possess high extraction ability toward actinides over lanthanides from acidic aqueous solution in our previous work. Herein we grafted phenanthrolineamide groups onto a large-pore three-dimensional cubic silica support by the reaction of DAPhen siloxane with KIT-6 substrate to prepare a novel uranium-selective sorbent, KIT-6-DAPhen. The as-synthesized sorbent was well-characterized by scanning electron microscopy, high-resolution transmission electron microscopy, N2 adsorption/desorption, X-ray diffraction, FT-IR, 13C cross-polarization magic-angle spinning NMR, and TGA techniques, which confirmed the consummation of the functionalization. Subsequently, the effects of contact time, solution pH, initial U(VI) concentration, and the presence of competing metal ions on the U(VI) sorption onto KIT-6-DAPhen sorbent were investigated in detail. It was found that KIT-6-DAPhen showed largely enhanced sorption capacity and excellent selectivity toward U(VI). The maximum sorption capacity of KIT-6-DAPhen at pH 5.0 reaches 328 mg of U/g of sorbent, which is superior to most of functionalized mesoporous silica materials. Density functional theory coupled with quasi-relativistic small-core pseudopotentials was used to explore the sorption interaction between U(VI) and KIT-6-DAPhen, which gives a sorption reaction of KIT-6-DAPhen + [UO2(H2O)5]2+ + NO3– ⇄ [UO2(KIT-6-DAPhen)(NO3)]+ + 5H2O. The findings of the present work provide new clues for developing new actinide sorbents by combining new ligands with various mesoporous matrixes.Keywords: DFT; KIT-6; mesoporous silica; phenanthroline; uranium;
Co-reporter:Jian-Hui Lan, Zhi-Fang Chai, Wei-Qun Shi
Science Bulletin 2017 Volume 62, Issue 15(Volume 62, Issue 15) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.scib.2017.07.007
Here we present a combined DFT and molecular dynamics study of uranyl (U(VI)) interaction mechanisms with the calcite (104) surface in aqueous solution. The roles of three anion ligands (CO32−, HCO3−, OH−) and solvation effect in U(VI) interaction with calcite have been evaluated. According to our calculations, water adsorbed on the calcite (1 0 4) surface prefers to exist in molecular state rather than dissociative state. Energy analysis indicate that the positively charged uranyl species prefers to form surface complexes on the surface, while neutral uranyl species may bind with the surface via both surface complexing and ion exchange reactions of U(VI) → Ca(II). In contrast, the negatively charged uranyl species prefer to interact with the surface via ion exchange reactions of U(VI) → Ca(II), and the one with UO2(CO3)2(H2O)2− as the reactant becomes the most favorable one in energy. We also found that uranyl adsorption increases the hydrophilic ability of the (104) surface to different extents, where the UO2(CO3)3Ca2 species contributes to the largest degree of energy changes (−53 kcal/mol). Our calculations proved that the (104) surface also has the ability to immobilize U(VI) via either surface complexing or ion exchange mechanisms under different pH values.Adsorption/incorporation of the uranyl species with equatorial ligands including the water, hydroxyl, carbonate, bicarbonate ligands on the (1 0 4) surface.Download high-res image (232KB)Download full-size image
Co-reporter:Zhiwei Huang, Zijie Li, Lirong Zheng, Limin Zhou, Zhifang Chai, Xiaolin Wang, Weiqun Shi
Chemical Engineering Journal 2017 Volume 328(Volume 328) pp:
Publication Date(Web):15 November 2017
DOI:10.1016/j.cej.2017.07.067
•Graphene oxide-chitosan hydrogel: an easily operated macroscopic adsorbent.•High adsorption capacity for U(VI) over a wide pH range.•Adsorption mechanism 1: at pH 3.5 and 5.0, surface complexation by –COO−, –OH, and –NH2.•Adsorption mechanism 2: at pH 8.3, UO2(hydrogel–NH2, C3–OH)(CO3)(H2O) proposed.Aiming at the efficient and convenient treatment of radioactive wastewater, a graphene oxide-chitosan aerogel (GO-CS) was fabricated and utilized for uranium(VI) elimination. The adsorption of U(VI) on the aerogel was evaluated as a function of contact time, solution pH, ionic strength, initial uranium concentration, and competing metal ions. High adsorption capacity for the uranium could be achieved over a wide pH range, e.g., 200, 319.9, and 384.6 mg/g at pH 3.5, 5.0, and 8.3, respectively. The interaction mechanism of U(VI) with GO-CS was systematically clarified by using Fourier transformation infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure spectroscopy (EXAFS). It was found that the U(VI) adsorption was mainly ascribed to the inner-sphere surface complexation by –COO−, –OH, and –NH2 groups anchored on the GO-CS and the involvement of these functional groups toward the coordination sphere was largely relevant to solution pH. At mild alkaline pH, –NH2 groups play a more important role, therefore leading to an extraordinarily high extraction of uranium from simulated seawater.Download high-res image (274KB)Download full-size image
Co-reporter:Tao Bo, Jian-Hui Lan, Yao-Lin Zhao, Chao-Hui He, Zhi-Fang Chai, Wei-Qun Shi
Journal of Nuclear Materials 2017 Volume 492(Volume 492) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.jnucmat.2017.05.026
The adsorption and dissociation behaviors of water on the UN (110) surface have been investigated by using DFT + U method in combination with ab initio atomistic thermodynamic simulations. The most stable adsorption site for H, O, and OH adsorption is the uranium bridge site. For a water monomer, the adsorption energies are −0.90, −3.23, and −4.46 eV for the most stable molecular, partially dissociative, and completely dissociative adsorption, respectively. The dissociation of water from H2O to OH and H has a very small energy barrier, while from OH to O and H has a high energy barrier of 1.63 eV. The coverage dependence for molecular adsorption is not obvious, while for partially dissociative and completely dissociative adsorption, the coverage dependence is quite obvious. Besides, we have investigated the adsorption of water under different temperature and pressure conditions by using the “ab initio atomistic thermodynamic” method.Download high-res image (369KB)Download full-size image
Co-reporter:Pin-Wen Huang, Cong-Zhi Wang, Zhi-Fang Chai, Wei-Qun Shi
Inorganica Chimica Acta 2017 Volume 463(Volume 463) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.ica.2017.04.014
The structure, bonding nature, and stability properties of several anhydrous and hydrate In-, Gd-, and Yb-carboxylates (M-CBX) and β-diketonates (M-BDK) used in neutrino liquid scintillator detectors have been investigated in two liquid scintillator (LS) solvents by density functional theory (DFT). Bonding energy and quantum theory of atoms in molecule (QTAIM) analyses reveal that the order of stability of these complexes is M-acetylacetone (M-ACAC) > M-tetramethyl-heptane-3,5-dionate (M-THD) > M-ethyl-hexanoate (M-EHA) ≈ M-methyl-valerate (M-MVA) ≈ M-tri-methyl-hexanate (M-TMHA) in LS solvent, while for the same ligand, binding energies increase in the order of Gd-L < Yb-L < In-L, which is inversely related to the metal ionic size. Therefore, In(ACAC)3 with better stability property might be more suitable for neutrino experiments than other metal-complexes. QTAIM study also shows that although electrostatic interaction dominates the metal-ligand bonding in In-, Gd-, and Yb-CBX complexes, some slight covalent character can be found in the In-CBX complexes. Calculated changes of Gibbs free energy (ΔG) of the solvent extraction reactions reveal that the products of the solvent extraction are mainly hydrated compounds. Therefore, more sophisticate method should be used to synthesize anhydrous complexes, which are supposed to have better solubility in LS solvent. The calculated ΔG values of potential dehydration reactions show that only limited types of hydrate Gd- and Yb-complexes can dehydrate in the gas phase at room temperature, while the situation is different in LS solvent. It is expected that our calculations can provide some useful information for future neutrino detection, radiochemical composition study of earth, and some other applications involving neutron capture.The structure and stability of several typical metal-organic complexes used in neutrino detectors have been investigated by quantum chemical calculations.Download high-res image (89KB)Download full-size image
Co-reporter:Ning Qu, Dong-Mei Su, Qun-Yan Wu, Wei-Qun Shi, Qing-Jiang Pan
Computational and Theoretical Chemistry 2017 Volume 1108(Volume 1108) pp:
Publication Date(Web):15 May 2017
DOI:10.1016/j.comptc.2017.03.011
•Relativistic DFT reveals UU bonding in diuranium diporphyrazines complexes.•Calculated UU distances, bond orders and stretching frequencies indicate the bonding interaction.•The U2 multiple bond is further proved by molecular orbital and QTAIM analyses.•An approximate correlation between uranium oxidation state and multiple bond number is built.To explore the uranium-uranium bonding nature, a ligated diuranium complex that could be experimentally possible would show features with no bridging ligand constraints (i.e. discrete or unsupported ligand), rigid ligand skeleton and suitable U-ligand bond. In this respect, we have designed and examined a series of diuranium diporphyrazines (Um2Pz2, m = II, III and IV) using relativistic density functional theory. Optimizations on all possible electron-spin isomers find that the triplet, quintet and quintet states are energetically lowest for Um2Pz2 (m = II, III and IV), respectively. They possess bond lengths of UU at 2.37, 2.46 and 2.91 Å, bond orders of 3.48, 3.33 and 2.11, and stretching vibrational frequencies of 239, 172 and 108 cm−1. Associated with the electronic-structure and QTAIM (quantum theory of atoms in molecules) analyses, a weak quadruple bond is suggested for the triplet state of UII2Pz2, and the triple and double bonds for UIII2Pz2, and UIV2Pz2, respectively. It shows that the uranium oxidation state approximately correlates with the number of multiple bonds.A relativistic DFT study of diuranium diporphyrazines reveals an approximate correlation between the uranium oxidation state (II, III and IV) and U2 multiple bond number (quadruple, triple and double). Bond lengths of UU, bond orders, stretching frequencies, as well as electronic structures and QTAIM support the assumption. The current study is expected to help understanding uranium-uranium bonding, particularly for divalent uranium whose experimental complexes remain scarce.Download high-res image (131KB)Download full-size image
Co-reporter:Yu-Juan Zhang, Zhang-Jian Zhou, Jian-Hui Lan, Chang-Chun Ge, Zhi-Fang Chai, Peihong Zhang, Wei-Qun Shi
Applied Surface Science 2017 Volume 426(Volume 426) pp:
Publication Date(Web):31 December 2017
DOI:10.1016/j.apsusc.2017.07.227
•V2C MXene as an adsorbent material for uranyl species is proposed and demonstrated.•Uranyl species with various ligands strongly chemisorb to hydroxylated V2C MXene.•The strong adsorption mechanism is explained by first-principles simulation methods.•The F-terminated MXene is less favorable for uranyl adsorption applications.Remediation of the contamination by long-lived actinide wastes is extremely important but also challenging. Adsorption based techniques have attracted much research attention for their potential as low-cost and effective methods to reduce the radioactive waste from solution. In this work, we have investigated the adsorption behavior of uranyl species [with the general form UO2(L1)x(L2)y(L3)z, where L1, L2 and L3 stand for ligands H2O, OH and CO3, respectively] on hydroxylated vanadium carbide V2C(OH)2 MXene nanosheets using density functional theory based simulation methods We find that all studied uranyl species can stably bond to hydroxylated MXene with binding energies ranging from −3.3 to −4.6 eV, suggesting that MXenes could be effective adsorbers for uranyl ions. The strong adsorption is achieved by forming two UO bonds with the hydroxylated Mxene. In addition, the axial oxygen atoms from the uranyl ions form hydrogen bonds with the hydroxylated V2C, further strengthening the adsorption. We have also investigated the effects of F termination on the uranyl adsorption properties of V2C nanosheets. UF bonds are in general weaker than UO bonds on the adsorption site, suggesting that F terminated Mexne is less favorable for uranyl adsorption applications.Download high-res image (193KB)Download full-size image
Co-reporter:Jie Li;Qunyan Wu;Xiangxue Wang;Zhifang Chai;Weiqun Shi;Jing Hou;Tasawar Hayat;Ahmed Alsaedi;Xiangke Wang
Journal of Materials Chemistry A 2017 vol. 5(Issue 38) pp:20398-20406
Publication Date(Web):2017/10/03
DOI:10.1039/C7TA06462D
A series of zirconium-based metal–organic frameworks (Zr-based MOFs) (UiO-66, UiO-66-NH2, UiO-66-OH, UiO-66-(OH)2 and UiO-67) with different surface charge properties and geometric dimensions were tested to decrease the concentration of graphene oxide (GO) nanosheets in aqueous solutions. Based on the experimental results and density functional theory (DFT) calculations, UiO-67 showed the highest adsorption capacity of all Zr-based MOFs studied herein. The π–π interaction/stacking, hydrogen bonding and Lewis acid–base interactions were the main cause for the removal of GO by negatively charged UiO-66-OH and UiO-66-(OH)2. Electrostatic attractions governed the association between GO and positively charged Zr-based MOFs (UiO-66, UiO-66-NH2 and UiO-67) via heteroaggregation. All adsorption and desorption isotherms of GO on UiO-66, UiO-66-NH2 or UiO-67 followed the linear model, and the obvious intercept (27–51 mg g−1) between adsorption–desorption isotherms disclosed that the GO adsorption over these MOFs was irreversible. This irreversible phenomenon was associated with a type of specific sheet–particle configuration, in which the particles of Zr-based MOFs were wrapped by GO nanosheets to form multilayered GO–MOF heteroaggregates with high geometric stability. The DFT calculations showed that the most stable adsorption structures were the geometries with the para-site of the linked ligand. Given the low-cost and simple preparation of Zr-based MOFs, it is clear that Zr-based MOFs could potentially act as coagulants for the efficient elimination of GO from aqueous solutions. This experimental evidence provides valuable information for the understanding of the interaction between GO and coagulants, and the potential fate, toxicity and migration of GO under natural conditions in aquatic environments, as well as in soils and sediments.
Co-reporter:Wencai Cheng;Congcong Ding;Qunyan Wu;Xiangxue Wang;Yubing Sun;Weiqun Shi;Tasawar Hayat;Ahmed Alsaedi;Zhifang Chai;Xiangke Wang
Environmental Science: Nano 2017 vol. 4(Issue 5) pp:1124-1131
Publication Date(Web):2017/05/18
DOI:10.1039/C7EN00114B
The competitive interaction of U(VI) and Sr(II) on graphene oxides (GOs) was studied by batch techniques, EXAFS analysis and DFT calculations. The batch results indicated that decreased sorption of Sr(II) on GOs was observed at C[U(VI)] < 0.2 mmol L−1 and enhanced sorption of Sr(II) was found at C[U(VI)] > 0.2 mmol L−1, whereas the presence of Sr(II) did not affect U(VI) sorption on GOs. The increased sorption of Sr(II) at C[U(VI)] > 0.2 mmol L−1 resulted from the new available sites provided by the precipitated U(VI) or adsorbed hydrolyzed U(VI) species according to EXAFS analysis. The occurrence of a U–C shell in the absence/presence of Sr(II) indicated that U(VI) tended to form inner-sphere surface complexes with GOs. For the Sr(II) interaction, a Sr–C shell was observed at a low U(VI) concentration, but not formed at a high U(VI) concentration, indicating the shift of inner-sphere to outer-sphere surface complexes with increasing U(VI) concentration. According to DFT calculation, the binding energy of GO–U(VI) (e.g., −40.3 kcal mol−1 for inner-sphere coordination) was significantly lower than that of GO–Sr(II) (−16.4 kcal mol−1), demonstrating that U(VI) was preferentially bound to GOs relative to Sr(II). These findings can provide a reliable prediction of the transport and fates of U(VI) and Sr(II) at the water–GO interface and open doorways for the application of GOs.
Co-reporter:Zhen-ni Xie;Lei Mei;Qun-yan Wu;Kong-qiu Hu;Liang-shu Xia;Zhi-fang Chai
Dalton Transactions 2017 vol. 46(Issue 23) pp:7392-7396
Publication Date(Web):2017/06/13
DOI:10.1039/C7DT01034F
The first reversible solid-state single-crystal-to-single-crystal isomerisation mediated by the change of uranyl-ligand coordination modes, that is from seven-coordinated uranium(VI) of α-UP to six-coordinated uranium(VI) of the supramolecular isomer, β-UP, has been achieved in the uranyl polyrotaxane system by a temperature-induced strategy.
Co-reporter:Lin Wang;Wuqing Tao;Liyong Yuan;Zhirong Liu;Qing Huang;Zhifang Chai;John K. Gibson;Weiqun Shi
Chemical Communications 2017 vol. 53(Issue 89) pp:12084-12087
Publication Date(Web):2017/11/07
DOI:10.1039/C7CC06740B
Though two-dimensional early transition metal carbides and carbonitrides (MXenes) have attracted extensive interest recently, their superb abilities in various scientific applications always suffer from the very narrow interlayer space inside the multilayered structure. Here we demonstrate an unprecedented large adsorption capacity enhancement of Ti3C2Tx toward radionuclide removal via a hydrated intercalation strategy. By rational control of the interlayer space, the potential for imprisoning the representative actinide U(VI) inside multilayered Ti3C2Tx was also confirmed.
Co-reporter:Shu-wen An, Lei Mei, Kong-qiu Hu, Chuan-qin Xia, Zhi-fang Chai and Wei-qun Shi
Chemical Communications 2016 vol. 52(Issue 8) pp:1641-1644
Publication Date(Web):23 Nov 2015
DOI:10.1039/C5CC09314G
Two novel tetra-nuclear uranyl-mediated two-fold interpenetrating networks, [U4O10(dbsf)3]2[H2bpp]2 and [U4O10(dbsf)3][H2bpp], have been hydrothermally synthesized from a semi-rigid carboxylic acid, H2dbsf, with the organic base, bpp, as the charge balancing agent and stacking template (H2dbsf = 4,4′-dicarboxybiphenyl sulfone, bpp = 1,3-di(4-pyridyl)propane).
Co-reporter:Lin Wang, Liyong Yuan, Ke Chen, Yujuan Zhang, Qihuang Deng, Shiyu Du, Qing Huang, Lirong Zheng, Jing Zhang, Zhifang Chai, Michel W. Barsoum, Xiangke Wang, and Weiqun Shi
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 25) pp:16396-16403
Publication Date(Web):June 7, 2016
DOI:10.1021/acsami.6b02989
Efficient nuclear waste treatment and environmental management are important hurdles that need to be overcome if nuclear energy is to become more widely used. Herein, we demonstrate the first case of using two-dimensional (2D) multilayered V2CTx nanosheets prepared by HF etching of V2AlC to remove actinides from aqueous solutions. The V2CTx material is found to be a highly efficient uranium (U(VI)) sorbent, evidenced by a high uptake capacity of 174 mg g–1, fast sorption kinetics, and desirable selectivity. Fitting of the sorption isotherm indicated that the sorption followed a heterogeneous adsorption model, most probably due to the presence of heterogeneous adsorption sites. Density functional theory calculations, in combination with X-ray absorption fine structure characterizations, suggest that the uranyl ions prefer to coordinate with hydroxyl groups bonded to the V-sites of the nanosheets via forming bidentate inner-sphere complexes.
Co-reporter:Ya-Lan Liu, Wen Zhou, Hong-Bin Tang, Zhi-Rong Liu, Kui Liu, Li-Yong Yuan, Yi-Xiao Feng, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2016 Volume 211() pp:313-321
Publication Date(Web):1 September 2016
DOI:10.1016/j.electacta.2016.06.061
In this work, the diffusion coefficients of Ho3+ at the Zn pool electrode and the Zn film electrode were firstly studied. Both semi-differential and semi-integral techniques were employed to analysis the cyclic voltammetry (CV) curves for the determination of the diffusion coefficients. The results showed that diffusion coefficients at Zn pool electrode and the Zn film electrode were close to each other by semi-differential technique. In addition, the co-reduction behaviors of Ho3+ and Zn2+ on W electrode were also investigated to determine the reactions of Ho with the Zn electrode. It was found that HoxZny intermetallic compounds would be formed by the co-reduction process, and the compositions of these HoxZny intermetallic compounds were estimated by the accumulated coulomb numbers of the relative anodic peaks on the CV curves. Moreover, electrodeposition of Ho3+ was carried out on both the inert W electrode and the liquid zinc electrode. X-ray diffraction (XRD) results showed that Ho2Zn17 and HoZn3 were obtained on the W electrode by the co-reduction process, whilst Ho2Zn17 was gained at the liquid zinc electrode by underpotential-deposition process. The microstructures of the intermetallic compounds were characterized by scanning electron microscopy (SEM).
Co-reporter:Xuemei Ren, Qunyan Wu, Huan Xu, Dadong Shao, Xiaoli Tan, Weiqun Shi, Changlun Chen, Jiaxing Li, Zhifang Chai, Tasawar Hayat, and Xiangke Wang
Environmental Science & Technology 2016 Volume 50(Issue 17) pp:9361-9369
Publication Date(Web):August 1, 2016
DOI:10.1021/acs.est.6b02934
This study establishes the relationship between the graphene oxide (GO) colloidal behavior and the co-adsorption of Cd(II) and phosphate (P(V)) on GO. Results reveal that the interactions among GO, Cd(II), and P(V) exhibit a significant dependence on solution chemistry and addition sequences and that these interactions subsequently affect the GO colloidal behavior. The GO aggregation is pH-dependent at pH < 4.0 and depends apparently on the binding ability of Cd(II) to GO at pH > 4.0. When the components were added simultaneously, the presence of P(V) enhances the GO binding capacity toward Cd(II), confirmed by theoretical calculation, resulting in the greater destabilizing influence of Cd(II) + P(V) on GO than Cd(II) at pH 3.0–9.5, while the formation of Cd3(PO4)2 precipitate leads to a lower destabilizing influence of Cd(II) + P(V) on GO than Cd(II) at pH > 9.5. Both pH and addition sequence affect the destabilizing ability of Cd(II) + P(V). These new insights are expected to provide valuable information not only for the application of GO as a potential adsorbent in multicomponent systems for heavy metal ion and oxyanion co-removal but also for the fate and risk assessment of GO after serving as heavy metal ion and oxyanion carrier.
Co-reporter:Huangjie Lu, Yaxing Wang, Congzhi Wang, Lanhua Chen, Weiqun Shi, Juan Diwu, Zhifang Chai, Thomas E. Albrecht-Schmitt, and Shuao Wang
Inorganic Chemistry 2016 Volume 55(Issue 17) pp:8570-8575
Publication Date(Web):August 5, 2016
DOI:10.1021/acs.inorgchem.6b01110
A unique two-dimensional inorganic cationic network with the formula [Th3O2(IO3)5(OH)2]Cl was synthesized hydrothermally. Its crystal structure can best be described as positively charged slabs built with hexanuclear thorium clusters connected by iodate trigonal pyramids. Additional chloride anions are present in the interlayer spaces but surprisingly are not exchangeable, as demonstrated by a series of CrO42– uptake experiments. This is because all chloride anions are trapped by multiple strong halogen–halogen interactions with short Cl–I bond lengths ranging from 3.134 to 3.333 Å, forming a special Cl-centered trigonal-pyramidal polyhedron as a newly observed coordination mode for halogen bonds. Density functional theory calculations clarified that electrons transformed from central Cl atoms to I atoms, generating a halogen–halogen interaction energy with a value of about −8.3 kcal mol–1 per Cl···I pair as well as providing a total value of −57.9 kcal mol–1 among delocalized halogen–halogen bonds, which is a new record value reported for a single halogen atom. Additional hydrogen-bonding interaction is also present between Cl and OH, and the interaction energy is predicted to be −8.1 kcal mol–1, confirming the strong total interaction to lock the interlayer Cl anions.
Co-reporter:Ran Zhao, Lei Mei, Lin Wang, Zhi-fang Chai, and Wei-qun Shi
Inorganic Chemistry 2016 Volume 55(Issue 20) pp:10125-10134
Publication Date(Web):September 28, 2016
DOI:10.1021/acs.inorgchem.6b00786
By employing a multidentate ligand, 2,2′-bipyridine-5,5′-dicarboxylic acid (H2bpdc), with both O-donors and N-donors, five uranyl-Cu(II)/Zn(II) heterometallic coordination polymers, (UO2)Cu(μ4-bpdc)(μ3-bpdc) (1-Cu), (UO2)Zn(μ4-bpdc)(μ3-bpdc) (1′-Zn), (UO2)CuCl(μ3-bpdc)(μ2-Hbpdc)(H2O) (2-Cu), (UO2)2Cu2Cl2(μ3-bpdc)2(μ2-Hbpdc)2(H2O)3·2H2O (2-Cu′), and (UO2)2Zn(μ3-SO4)(μ4-bpdc)(μ3-bpdc)(H2O)3 (3-Zn), were prepared under hydrothermal conditions. Thermal stability and luminescent properties of 1-Cu, 1′-Zn, 2-Cu, and 3-Zn were also investigated. Isostructural compounds 1-Cu and 1′-Zn both have a three-dimensional (3D) framework built by polycatenating of two sets of paralleling two-dimensional (2D) grids with octahedral transition metal cations (Cu or Zn) as the cross-linking nodes. As far as we know, compounds 1-Cu and 1′-Zn are the first two cases that possess polycatenated networks in heterometallic uranyl-organic coordination polymers. Compound 2-Cu contains 3-fold interpenetrated 2D networks which are built by the connection of [(UO2)2(bpdc)2(Hbpdc)2]2– secondary building units and Cu(II). A one-dimensional tilted ladder-like structure in 2-Cu′ is constructed by uranyl-bpdc chains connected by Cu(II) and Hbpdc–. Compound 3-Zn displays a layered-like 2D network contain an unusual [(UO2)2Zn(μ3-SO4)] unit. Interestingly, different anions could lead to the change of coordination sites of transition metal cations, resulting in structural diversity of heterometallic uranyl-organic frameworks.
Co-reporter:Q.-Y. Wu, J.-H. Lan, C.-Z. Wang, Z.-P. Cheng, Z.-F. Chai, J. K. Gibson and W.-Q. Shi
Dalton Transactions 2016 vol. 45(Issue 7) pp:3102-3110
Publication Date(Web):05 Jan 2016
DOI:10.1039/C5DT04540A
Recently, the +2 formal oxidation state in soluble molecular complexes for lanthanides (La–Nd, Sm–Lu) and actinides (Th and U) has been discovered [W. J. Evans, et al., J. Am. Chem. Soc., 2011, 133, 15914; J. Am. Chem. Soc., 2012, 134, 8420; J. Am. Chem. Soc., 2013, 135, 13310; Chem. Sci., 2015, 6, 517]. To explore the nature of the bonding and stabilities of the low-valent actinide complexes, a series of divalent actinide species, [AnCp′3]− (AnTh–Am, Cp′ = [η5-C5H4(SiMe3)]−) have been investigated in THF solution using scalar relativistic density functional theory. The electronic structures and electron affinity properties were systematically studied to identify the interactions between the +2 actinide ions and Cp′ ligands. The ground state electron configurations for the [AnCp′3]− species are [ThCp′3]− 6d2, [PaCp′3]− 5f26d1, [UCp′3]− 5f36d1, [NpCp′3]− 5f5, [PuCp′3]− 5f6, and [AmCp′3]− 5f7, respectively, according to the MO analysis. The total bonding energy decreases from the Th- to the Am-complex and the electrostatic interactions mainly dominate the bonding between the actinide atom and ligands. The electron affinity analysis suggests that the reduction reaction of AnCp′3 → [AnCp′3]− should become increasingly facile across the actinide series from Th to Am, in accord with the known An(III/II) reduction potentials. This work expands the knowledge on the low oxidation state chemistry of actinides, and further motivates and guides the synthesis of related low oxidation state compounds of 5f elements.
Co-reporter:Kong-Qiu Hu, Liu-Zheng Zhu, Cong-Zhi Wang, Lei Mei, Yun-Hai Liu, Zeng-Qiang Gao, Zhi-Fang Chai, and Wei-Qun Shi
Crystal Growth & Design 2016 Volume 16(Issue 9) pp:4886
Publication Date(Web):July 18, 2016
DOI:10.1021/acs.cgd.6b00429
Novel uranyl coordination polymers, UO2(bqdc)(phen)·H2O (1), [UO2(μ-OH)(bqdc)(H2bpy)0.5(H2O)] (2), Na[(UO2)2(bqdc)3Na(H2O)2] (3), and [Na(bqdc)0.5(bpp)(H2O)] (4) (H2bqdc = 2,2′-biquinoline-4,4′-dicarboxylic acid; phen = 1,10-phenanthroline; bpy = 4,4′-bipyridine; bpp = 1,3-di(4-pyridyl)propane), with bqdc2– ligands have been successfully synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction, Infrared spectroscopy (IR), thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD). The topological structures feature 1D chain to 3D framework by altering N-donor ancillary ligands. Compound 1 shows a 1D wave-shaped zigzag chain structure and further extends to a two-dimensional (2D) layer through π···π interactions between the quinoline ring of bqdc2– ligand and benzene ring of phen ligand. The uranium adopts an approximate hexagonal bipyramidal coordination geometry with the equatorial plane warped to the unusual chair conformation. Compound 2 features rectangular-shaped units with space range of 12.28(2) Å × 7.16(3) Å, exhibiting an intriguing 2D uranyl double layered motif formed by 1D ladder chains. The protonated bpy molecules provide space filling and form hydrogen bonds with the layers. Compound 3 is based upon 3D heterometallic frameworks constructed from UO22+, Na+, and bqdc2– ligands. The most striking feature of compound 3 is that one sodium ion is located in the middle of two adjacent uranyl ions, forming the trinuclear heterometal clusters (U2Na), which are further connected by bqdc2– ligands to generate UOFs with the cavity size of 10.07(0) Å × 13.86(2) Å. The local 1D structure of compound 3 is similar to the zigzag chain of compound 1. Compound 4 displays 1D chain structure and further extends to 3D framework via hydrogen bond and π···π interactions. Moreover, the electronic structural and bonding properties of the uranyl compounds 1–3 have been systematically explored by density functional theory (DFT) calculations.
Co-reporter:Tao Bo, Jian-Hui Lan, Yu-Juan Zhang, Yao-Lin Zhao, Chao-Hui He, Zhi-Fang Chai and Wei-Qun Shi
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 19) pp:13255-13266
Publication Date(Web):11 Apr 2016
DOI:10.1039/C6CP01175F
The interfacial interaction of uranium mononitride (UN) with water from the environment unavoidably leads to corrosion of nuclear fuels, which affects a lot of processes in the nuclear fuel cycle. In this work, the microscopic adsorption behaviors of water on the UN(001) surface as well as water dissociation and accompanying H2 formation mechanisms have been investigated on the basis of DFT+U calculations and ab initio atomistic thermodynamics. For adsorption of one H2O monomer, the predicted adsorption energies are −0.88, −2.07, and −2.07 eV for the most stable molecular, partially dissociative, and completely dissociative adsorption, respectively. According to our calculations, a water molecule dissociates into OH and H species via three pathways with small energy barriers of 0.78, 0.72, and 0.85 eV, respectively. With the aid of the neighboring H atom, H2 formation through the reaction of H* + OH* can easily occur via two pathways with energy barriers of 0.61 and 0.36 eV, respectively. The molecular adsorption of water shows a slight coverage dependence on the surface while this dependence becomes obvious for partially dissociative adsorption as the water coverage increases from 1/4 to 1 ML. In addition, based on the “ab initio atomistic thermodynamic” simulations, increasing H2O partial pressure will enhance the stability of the adsorbed system and water coverage, while increasing temperature will decrease the H2O coverage. We found that the UN(001) surface reacts easily with H2O at room temperature, leading to dissolution and corrosion of the UN fuel materials.
Co-reporter:Lei Mei, Zhen-ni Xie, Kong-qiu Hu, Lin Wang, Li-yong Yuan, Zi-jie Li, Zhi-fang Chai and Wei-qun Shi
Dalton Transactions 2016 vol. 45(Issue 34) pp:13304-13307
Publication Date(Web):20 Jul 2016
DOI:10.1039/C6DT02704K
The first 3D actinide polyrotaxane framework (named IHEP-URCP-2) has been obtained based on windmill-like six-connected high-nuclear oligomeric uranyl nodes under hydrothermal conditions. Notably, the in situ formed pseudorotaxane ligand simultaneously plays dual roles of both a bulky pseudorotaxane linker and a supramolecular guest.
Co-reporter:Han Wu, Qun-Yan Wu, Cong-Zhi Wang, Jian-Hui Lan, Zhi-Rong Liu, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2016 vol. 45(Issue 19) pp:8107-8117
Publication Date(Web):30 Mar 2016
DOI:10.1039/C6DT00296J
Although many heterocyclic N-donor ligands have shown excellent competence for separating actinides from lanthanides, an explanation for why some ligands work whereas others fail is very fundamental but greatly needs to be addressed for designing novel and efficient extractants. In this work, we systematically investigated four phenanthroline-derived ligands, DHDIPhen, BQPhen, Ph2-BTPhen and CyMe4-BTPhen, and their coordination geometrical properties and formation reactions with Am(III) and Eu(III) ions by quasi-relativistic density functional theory. The calculated hardness of ligands, which may help to determine their selectivity toward actinides and lanthanides, yielded an order, from the softest to the hardest, as follows: Ph2-BTPhen < CyMe4-BTPhen < BQPhen < DHDIPhen. It shows that the intramolecular hydrogen bonds and size of a ligand cavity are two dominant factors for metal-ion complexation. Natural population analysis (NPA) reveals that the 5d/6d orbitals of Eu/Am accept significantly more electrons than other orbitals, but partial density of states and molecular orbital analysis prove that the d orbitals with more accepted electrons have little contribution to the metal–ligand bonds. The thermodynamic results suggest that ligand protonation does have a great influence on the complexation of ligands with metal ions but does not change the selectivity of ligands toward metal ions. This work can help in-depth understanding the differences of selectivity of various structurally similar ligands and provide more theoretical insights for designing more innovative ligands for Ln/An separation.
Co-reporter:Qun-Yan Wu, Cong-Zhi Wang, Jian-Hui Lan, Zhi-Fang Chai and Wei-Qun Shi
RSC Advances 2016 vol. 6(Issue 74) pp:69773-69781
Publication Date(Web):18 Jul 2016
DOI:10.1039/C6RA14906E
To study the coordination modes and the binding affinities of uranyl ions with serine and phosphoserine, 1:1, 1:2 and 1:3 type complexes of a uranyl ion with these ligands were optimized at the B3LYP/ECP60MWB-SEG/6-311+G(d)/SMD level of theory in an aqueous solution. The analyses of the electronic energies show that the uranyl ion tends to adopt a penta-coordination mode and the binding affinity of the uranyl ion toward three functional groups follows the order of –PO42− > –COO− > –PO4H−. The changes of the Gibbs free energy (ΔGsol) for the studied reactions suggest that the uranyl ion prefers to form a 1:3 type complex with these ligands. Moreover, the absolute values of ΔGsol increase for the phosphorylated serine with the same type of reaction. Based on the thermodynamic results, a higher solution pH is more favorable for uranyl ion coordination with phosphoserine. This work could render theoretical insights into the specific coordination modes of uranyl ions with serine/phosphoserine under different conditions and provide useful information for further study on the interactions between actinide cations with peptides and proteins.
Co-reporter:Juan Luo;Congzhi Wang;Jianhui Lan;Qunyan Wu;Yuliang Zhao
Science China Chemistry 2016 Volume 59( Issue 3) pp:324-331
Publication Date(Web):2016 March
DOI:10.1007/s11426-015-5489-4
Separation of trivalent lanthanides (Ln(III)) and actinides (An(III)) is a key issue in the advanced spent nuclear fuel reprocessing. In the well-known trivalent actinide lanthanide separation by phosphorus reagent extraction from aqueous komplexes (TALSPEAK) process, the organophosphorus ligand HDEHP (di-(2-ethylhexyl) phosphoric acid) has been used as an efficient reagent for the partitioning of Ln(III) from An(III) with the combination of a holdback reagent in aqueous lactate buffer solution. In this work, the structural and electronic properties of Eu3+ and Am3+ complexes with HDEHP in nitric acid solution have been systematically explored by using scalar-relativistic density functional theory (DFT). It was found that HDEHP can coordinate with M(III) (M=Eu, Am) cations in the form of hydrogen-bonded dimers HL2- (L=DEHP), and the metal ions prefer to coordinate with the phosphoryl oxygen atom of the ligand. For all the extraction complexes, the metal-ligand bonds are mainly ionic in nature. Although Eu(III) complexes have higher interaction energies, the HL2- dimer shows comparable affinity for Eu(III) and Am(III) according to thermodynamic analysis, which may be attributed to the higher stabilities of Eu(III) nonahydrate. It is expected that this work could provide insightful information on the complexation of An(III) and Ln(III) with HDEHP at the molecular level.
Co-reporter:Zhi-Qiang Bai, Li-Yong Yuan, Lin Zhu, Zhi-Rong Liu, Sheng-Qi Chu, Li-Rong Zheng, Jing Zhang, Zhi-Fang Chai and Wei-Qun Shi
Journal of Materials Chemistry A 2015 vol. 3(Issue 2) pp:525-534
Publication Date(Web):11 Nov 2014
DOI:10.1039/C4TA04878D
Metal–organic frameworks (MOFs) have recently been receiving increasing attention in various scientific fields, including nuclear industry, due to their unique properties. In this work, the acid-resistant chromium-based MOF, MIL-101, and its amino derivatives were prepared to explore their potential usage in separation, removal and/or recovery of radionuclides from aqueous solutions. The synthesized MIL-101-NH2, MIL-101-ED (ED = Ethanediamine), and MIL-101-DETA (DETA = Diethylenetriamine) were characterized by X-ray diffraction spectrometry (XRD), infrared spectrometry (IR), N2 adsorption–desorption measurements, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), which confirm the successful modification of amino groups and the preservation of porous structures. The sorption performances of these materials toward U(VI) from an aqueous solution were investigated in detail. It was found that all the amine-grafted MOFs were highly efficient in capturing U(VI) compared to raw MIL-101. The sorption capacity of these MOFs for U(VI) sorption follows the order of MIL-101-DETA > MIL-101-ED > MIL-101-NH2 > MIL-101, in which MIL-101-DETA possesses the highest sorption capacity of 350 mg g−1 at pH ∼5.5. Moreover, the sorbed U(VI) can be easily desorbed by lowering the pH (pH ≤ 3.0), and the prepared materials also display a desirable selectivity toward U(VI) in a solution containing a range of competing ions. Based on the FTIR and EXAFS characterizations, the sorption mode of U(VI) onto MOFs is fully discussed. This work promises to provide a facile approach for developing acid-resistant MOFs toward a highly efficient and selective extraction of radionuclides from aqueous solutions.
Co-reporter:Lei Mei, Lin Wang, Li-yong Yuan, Shu-wen An, Yu-liang Zhao, Zhi-fang Chai, Peter C. Burns and Wei-qun Shi
Chemical Communications 2015 vol. 51(Issue 60) pp:11990-11993
Publication Date(Web):22 Jun 2015
DOI:10.1039/C5CC04409J
The assembly of two-dimensional (2D) large channel uranyl–organic polyrotaxane networks as well as structural regulation of uranyl-bearing units using jointed cucurbit[6]uril-based pseudorotaxanes with integral rigidity based on supramolecular inclusion is presented for the first time. This construction strategy concerning controlling molecular integral rigidity based on supramolecular inclusion may afford an entirely new methodology for coordination chemistry.
Co-reporter:Shu-wen An, Lei Mei, Cong-zhi Wang, Chuan-qin Xia, Zhi-fang Chai and Wei-qun Shi
Chemical Communications 2015 vol. 51(Issue 43) pp:8978-8981
Publication Date(Web):10 Apr 2015
DOI:10.1039/C5CC02646F
The first actinide triple helices, including two supramolecular conformational isomers of uranium(VI), have been synthesized with the aid of a flexible V-shaped ligand and a rigid aromatic base. The isomers exhibit an intriguing pH-dependent structural evolution and a kinetically-controlled transformation via a novel conformational rearrangement of the organic base.
Co-reporter:Li-Yong Yuan, Man Sun, Lei Mei, Lin Wang, Li-Rong Zheng, Zeng-Qiang Gao, Jing Zhang, Yu-Liang Zhao, Zhi-Fang Chai, and Wei-Qun Shi
Inorganic Chemistry 2015 Volume 54(Issue 4) pp:1992-1999
Publication Date(Web):January 28, 2015
DOI:10.1021/ic502890w
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 UO22+ 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.
Co-reporter:Lei Mei; Qun-yan Wu; Shu-wen An; Zeng-qiang Gao; Zhi-fang Chai
Inorganic Chemistry 2015 Volume 54(Issue 22) pp:10934-10945
Publication Date(Web):October 22, 2015
DOI:10.1021/acs.inorgchem.5b01988
A unique case of a uranyl-silver heterometallic 3-fold interpenetrating network (U-Ag-2,6-DCPCA) from a multifunctionalized organic ligand, 2,6-dichloroisonicotinic acid, in the presence of uranyl and silver ions is reported. It is the first report of a heterometallic uranyl–organic interpenetrating network or framework. Notably, a (4,4)-connected uranyl building unit in U-Ag-2,6-DCPCA, which is available through combined influences of structural halogenation and silver ion additive on uranyl coordination, plays a vital role in the formation of a 3-fold interpenetrating network. Halogen substitution effectively changes structural features and coordination behaviors of isonicotinate ligand and contributes to the control of uranyl coordination. Meanwhile, it exerts influence on the stabilization of 3-fold interpenetrating networks by halogen–halogen interactions. Theoretical calculation suggests that the silver ion should mainly serve as an inductive factor of uranyl species through strong Ag–N binding affinity, directly leading to the formation of a (4,4)-connected uranyl building unit and finally a heterometallic 3-fold interpenetrating network. Related experimental results, especially an interesting postsynthetic metalation, afford further evidence of this induction effect.
Co-reporter:Xiangxue Wang, Shubin Yang, Weiqun Shi, Jiaxing Li, Tasawar Hayat, and Xiangke Wang
Environmental Science & Technology 2015 Volume 49(Issue 19) pp:11721-11728
Publication Date(Web):September 15, 2015
DOI:10.1021/acs.est.5b02679
Herein the sorption of Eu(III) and 243Am(III) on multiwalled carbon nanotubes (CNTs) are studied, and the results show that Eu(III) and 243Am(III) could form strong inner-sphere surface complexes on CNT surfaces. However, the sorption of Eu(III) on CNTs is stronger than that of 243Am(III) on CNTs, suggesting the difference in the interaction mechanisms or properties of Eu(III) and 243Am(III) with CNTs, which is quite different from the results of Eu(III) and 243Am(III) interaction on natural clay minerals and oxides. On the basis of the results of density functional theory calculations, the binding energies of Eu(III) on CNTs are much higher than those of 243Am(III) on CNTs, indicating that Eu(III) could form stronger complexes with the oxygen-containing functional groups of CNTs than 243Am(III), which is in good agreement with the experimental results of higher sorption capacity of CNTs for Eu(III). The oxygen-containing functional groups contribute significantly to the uptake of Eu(III) and 243Am(III), and the binding affinity increases in the order of ≡S—OH < ≡S—COOH < ≡S—COO–. This paper highlights the interaction mechanism of Eu(III) and 243Am(III) with different oxygen-containing functional groups of CNTs, which plays an important role for the potential application of CNTs in the preconcentration, removal, and separation of trivalent lanthanides and actinides in environmental pollution cleanup.
Co-reporter:Ya-Lan Liu, Guo-An Ye, Kui Liu, Li-Yong Yuan, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2015 Volume 168() pp:206-215
Publication Date(Web):20 June 2015
DOI:10.1016/j.electacta.2015.03.219
The electrochemical behaviors of La(III) on W and Zn-coated W electrodes was investigated, respectively, in the LiCl-KCl eutectic by cyclic voltammetry (CV) and open circuit chronopotentiometry (OCP). On an inert W electrode, the reduction of La(III) takes place at about −2.11 V in a single soluble-insoluble electrochemical step La(III)/La(0). In contrast, the electrochemical reduction of La(III) on a Zn-coated W electrode was observed at less cathodic potentials than at the inert W electrode. The potential shift was mainly caused by the formation of La-Zn intermetallic compounds, in which the activity of La was largely decreased compared to that in pure La metal. From CV results, six peaks corresponding to the formation of La-Zn intermetallic compounds were observed. By the OCP technique, eight plateaus corresponding to the co-existence of two phases of La-Zn intermetallic compound such as LaZn-LaZn2, LaZn2-LaZn4, LaZn4-LaZn5, LaZn5 -La3Zn22, La3Zn22-La2Zn17, La2Zn17-LaZn11, LaZn11-LaZn13 and LaZn13-Zn were observed. The formation energy of each La-Zn intermetallic compound, and the overall formation constant were estimated from OCP measurements at 723 K. X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) were employed to characterize the potentiostatic and galvanostatic electrolysis products. The presences of LaZn, LaZn2, LaZn5 and La2Zn17 in the electrolysis products were identified.
Co-reporter:Tao Zheng, Qun-Yan Wu, Yang Gao, Daxiang Gui, Shiwen Qiu, Lanhua Chen, Daopeng Sheng, Juan Diwu, Wei-Qun Shi, Zhifang Chai, Thomas E. Albrecht-Schmitt, and Shuao Wang
Inorganic Chemistry 2015 Volume 54(Issue 8) pp:3864-3874
Publication Date(Web):March 27, 2015
DOI:10.1021/acs.inorgchem.5b00024
Systematic control of the reactions between U(VI) and 1,4-phenylenebis(methylene))bis(phosphonic acid) (pmbH4) allows for alterations in the bonding between these constituents and affords three uranyl phosphonate compounds with chiral one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) structures, namely, [TPA][UO2(pmbH3)(pmbH2)H2O]·2H2O (1), [NH4]2[UO2(pmb)] (2), UO2(pmbH2) (3), and the first uranyl mixed phosphite/phosphonate compound [TMA]2[(UO2)2(pmb)(HPO3)] (4) (TPA = NPr4+, TMA = NMe4+). These compounds crystallize in the space groups P212121, P1̅, P21/c, and Cmcm, respectively. Further investigation of the local uranyl coordination environment reveals that in 1 only oxygen atoms from P═O moieties ligate the uranium centers; whereas in 2 only P–O– oxygen atoms are involved in bonding and yield a layered topology. Compound 3 differs sharply from the first two in that conjugated P═O and P–O– oxygen atoms chelate the uranium centers resulting in a 3D framework. In compound 4, a phosphonate group bridges three uranyl centers further coordinated with a phosphite ligand HPO32–, which is a product of pmbH4 decomposing, forming a 2D layered structure. Compounds 3 and 4 also contain a different coordination environment for U(VI) than that found in 1 or 2. In this case, tetragonal bipyramidal UO6 units occur instead of the far more common UO7 pentagonal bipyramids found in 1 and 2. Interestingly, 1 converts to 3 at elevated reaction temperatures, indicating that the formation of 1 is likely under kinetic control. This is supported by thermal analysis, which reveals that 3 has higher thermal stability than 1 or 2. UV–vis–near-IR absorption and fluorescence spectroscopy show that the absorption and photoluminescence intensity increases from 1 to 4. Density functional theory electronic structure calculations provide insight into the nature of the interactions between U(VI) and the phosphonate ligands.
Co-reporter:Kui Liu, Ya-Lan Liu, Li-Yong Yuan, Lu Wang, Lin Wang, Zi-Jie Li, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2015 Volume 174() pp:15-25
Publication Date(Web):20 August 2015
DOI:10.1016/j.electacta.2015.05.161
This work presents a study of electrochemistry of holmium in the LiCl-KCl eutectic by applying a series of electrochemical techniques on a tungsten electrode at the temperature range of 684–809 K. The reduction of Ho(III) cations in the LiCl-KCl eutectic is a one step process with the transfer of three electrons. The diffusion coefficients of the Ho(III) is temperature dependent and can be expressed aslnDHo(III)=−446lT−1−5.498. The activation energy for the diffusion of Ho(III) in the LiCl-KCl eutectic was also calculated to be 37.09 kJ/mol. The apparent standard potential of Ho(III) can be described asEHo(III)/Hoθ,(vs.Cl2/Cl−1)=−3.450+5.789×10−4T/V and the apparent Gibbs free energy for the formation of HoCl3 in the LiCl-KCl eutectic can be expressed as: ΔGHoCl3θ,(vs.Cl2/Cl−1)=−998.62+0.1676T (kJ/mol). The thermodynamic properties of six AlyHox intermetallic compounds were determined by open circuit chronopotentiometry (OCP) at the temperature of 723 and 773 K. AlyHox intermetallic compound samples were prepared by potentiostatic electrolysis in the LiCl-KCl-AlCl3-Ho2O3 and LiCl-KCl-HoCl3 melts on an aluminium electrode at 773 K, respectively. Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) and X-ray diffraction (XRD) characterizations identified the formation of three intermetallic compounds (Al17Ho2, Al3Ho and Al2Ho). As far as we know, this is the first time that intermetallic compound Al17Ho2 was obtained by an electrochemical method.
Co-reporter:Ya-Lan Liu, Guo-An Ye, Li-Yong Yuan, Kui Liu, Yi-Xiao Feng, Zi-Jie Li, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2015 Volume 158() pp:277-286
Publication Date(Web):10 March 2015
DOI:10.1016/j.electacta.2015.01.128
In this work, AlCl3 was employed to chloridize ThO2 and La2O3 with the formation of ThCl4 and LaCl3 in the LiCl-KCl eutectic at 773 K. The chlorination can be accomplished in less than one hour, displaying a fast chlorination kinetic. Cyclic voltammetry (CV) technique was used to evaluate the feasibility of the separation of Th4+ from La3+ through forming Th-Al alloys. The results showed that the disparity between the deposition potentials of Th-Al and La-Al alloys was approximately 0.2 V at 773 K, which is theoretically sufficient for the separation of Th4+ from La3+. Subsequently, the separation of Th4+ from La3+ was carried out on Al cathodes by galvanostatic electrolysis and potentiostatic electrolysis at the temperature of 773 K. During the separation process, the concentrations of Th4+ and La3+ ions were monitored by both Square Wave Voltammetry (SWV) on a W electrode and ICP-AES analysis of the melt. The deposited products were characterized by the scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectrometer (ICP-AES). Finally, by potentiostatic electrolysis at −1.20 V for 48 h in an Al3+ ion sufficient system, the recovery rate of Th was determined to be 97.1%. In addition, the separation factor (SF) of Th to La of 1367.4 was achieved.
Co-reporter:Liu-Zheng Zhu, Cong-Zhi Wang, Lei Mei, Lin Wang, Yun-Hai Liu, Zhen-Tai Zhu, Yu-Liang Zhao, Zhi-Fang Chai and Wei-Qun Shi
CrystEngComm 2015 vol. 17(Issue 15) pp:3031-3040
Publication Date(Web):11 Mar 2015
DOI:10.1039/C5CE00223K
Two novel uranyl coordination polymers, namely, UO2(bptc)(H2bpy)·(bpy) (1) and (UO2)3(bptc)1.5(phen)2(H2O)2·H2O (2) (H4bptc = 3,3′,4,4′-benzophenonetetracarboxylic acid; bpy = 4,4′-bipyridine; phen = 1,10-phenanthroline), have been obtained via a hydrothermal method based on a semi-rigid aromatic tetracarboxylic ligand and two different auxiliary or templating N-containing ligands. Complex 1 shows a one-dimensional (1D) structure derived from double chains with two types of rings arranged alternately, which further exhibits an intriguing 3D supramolecular network induced by diverse non-covalent interactions. Complex 2 displays a dislocated “double floor” of a 2D structure (2D zigzag layers), in which the carboxylate groups of the bptc4− ligand adopt a variety of fascinating bridging modes. In addition, quantum chemical calculations were used to investigate the coordination properties and bonding nature of the as-synthesized complexes, and the results indicate that in these two complexes the 5f, 6d, and 7p orbitals of uranium and 2p orbitals of O and N atoms mainly contribute to the covalency of the U–O and U–N bonds.
Co-reporter:Lei Mei, Cong-zhi Wang, Lin Wang, Yu-liang Zhao, Zhi-fang Chai, and Wei-qun Shi
Crystal Growth & Design 2015 Volume 15(Issue 3) pp:1395-1406
Publication Date(Web):February 12, 2015
DOI:10.1021/cg501783d
Actinide-based metal–organic materials have drawn much attention due to their intriguing 5f bonding properties and promising applications in nuclear fuels and other fields. Introduction of weak interactions, such as halogen bonds, into actinide–organic hybrid materials will provide them with more flexibility and dynamics. The first case of halogen bonded three-dimensional (3D) uranyl–organic supramolecular frameworks with regular nanoscale channels has been obtained from multifunctional halogen-substituted isonicotinic acids. Distinct from conventional halogen bonded uranyl–organic frameworks, the supramolecular networks obtained here consist of three-component cocrystals and have been assemblied by intensive supramolecular networks to obtain an extended 3D geometry. Moreover, secondary “X3” and “X6” halogen–halogen interactions resulting from the driving forces of primary hydrogen bonds have been found and analyzed by quantum chemical calculation, indicating their feature of weak bonding and special geometry. It is notable that this unprecedented type of “X6” synthon, especially for “Br6”, represents a new pattern of halogen–halogen interaction. When halogen substitution of the organic precursor is changed, another type of halogen bonded and hydrogen bonded 3D uranyl–organic framework with two-dimensional layered networks and cross-linking agents formed in situ was acquired. Finally, reversible transformation of 3D uranyl–organic supramolecular frameworks is available through loss and regain of water involving in hydrogen bonding networks and thus affords them structural dynamics.
Co-reporter:Cong-Zhi Wang, John K. Gibson, Jian-Hui Lan, Qun-Yan Wu, Yu-Liang Zhao, Jun Li, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2015 vol. 44(Issue 39) pp:17045-17053
Publication Date(Web):27 Aug 2015
DOI:10.1039/C5DT02811F
Synthesis of complexes with direct actinide–actinide (An–An) bonding is an experimental ‘holy grail’ in actinide chemistry. In this work, a series of actinide dimetallocenes An2Cp*2 (Cp* = C5(CH3)5, An = Th–Pu) with An–An multiple bonds have been systematically investigated using quantum chemical calculations. The coaxial Cp*–An–An–Cp* structures are found to be the most stable species for all the dimetallocenes. A Th–Th triple bond is predicted in the Th2Cp*2 complex, and the calculated An–An bond orders decrease across the actinide series from Pa to Pu. The covalent character of the An–An bonds is analyzed by using natural bond orbitals (NBO), molecular orbitals (MO), the quantum theory of atoms in molecules (QTAIM), and electron density difference (EDD). While Th 6d orbitals dominate the Th–Th bonds in Th2Cp*2, the An 6d-orbital characters decrease and 5f-orbital characters increase for complexes from Pa2Cp*2 to Pu2Cp*2. All these actinide dimetallocenes are stable in the gas phase relative to the AnCp* reference at room temperature. Based on the reactions of AnCp*2 and An, Th2Cp*2, Pa2Cp*2 and possibly also U2Cp*2 should be accessible as isolated molecules under suitable synthetic conditions. Our results shed light on the molecular design of ligands for stabilizing actinide–actinide multiple bonds.
Co-reporter:Han Wu, Qun-Yan Wu, Cong-Zhi Wang, Jian-Hui Lan, Zhi-Rong Liu, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2015 vol. 44(Issue 38) pp:16737-16745
Publication Date(Web):19 Aug 2015
DOI:10.1039/C5DT02528A
Due to the similar chemical properties of actinides An(III) and lanthanides Ln(III), their separation in spent nuclear fuel reprocessing is extremely challenging. A 1,10-phenanthroline dipicolinamide-based ligand (PhenBHPPA) has been identified to possess a selectivity for Am(III) over Eu(III) and could potentially be used for group actinide extraction. In this study, quasi-relativistic density functional theoretical calculations have been used to disclose the interaction mechanisms of Am(III) and Eu(III) complexes with PhenBHPPA. The electronic structures, bonding nature, QTAIM (Quantum Theory of Atoms in Molecules) analyses and thermodynamic behaviors of the Am(III) and Eu(III) complexes with PhenBHPPA have been explored in detail. According to the Wiberg bond indices (WBIs) and QTAIM analyses, interactions between the ligand and metal cations (Am(III) and Eu(III)) exhibit a weakly covalent character. Thermodynamic analyses show that the charged complexes [ML(NO3)2]+ appear to be the most stable species in the complexation processes. Moreover, it is more energetically favorable for PhenBHPPA to bind to Am(III) compared to Eu(III). Our study could render new insights into understanding the selectivity of the ligand towards minor actinides and the separation of An(III) from Ln(III) via liquid–liquid extraction.
Co-reporter:Cheng-Liang Xiao, Cong-Zhi Wang, Lei Mei, Xin-Rui Zhang, Nathalie Wall, Yu-Liang Zhao, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2015 vol. 44(Issue 32) pp:14376-14387
Publication Date(Web):08 Jul 2015
DOI:10.1039/C5DT01766A
The tetradentate N,N′-diethyl-N,N′-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) ligand with hard–soft donor atoms has been demonstrated to be promising for the group separation of actinides from highly acidic nuclear wastes. To identify the formed complexes of this ligand with actinides and lanthanides, electrospray ionization mass spectrometry (ESI-MS) combined with density functional theory (DFT) calculations was used to probe the possible complexation processes. The 1:2 Eu–L species ([EuL2(NO3)]2+) can be observed in ESI-MS at low metal-to-ligand ([M]/[L]) ratios, whereas the 1:1 Eu–L species ([EuL(NO3)2]+) can be observed when the [M]/[L] ratio is higher than 1.0. However, ([UO2L(NO3)]+) is the only detected species for the uranyl complexes. The [ThL2(NO3)2]2+ species can be observed at low [M]/[L] ratios; the 1:2 species ([ThL2(NO3)]3+) and a new 1:1 species ([ThL(NO3)3]+) can be detected at high [M]/[L] ratios. Collision-induced dissociation (CID) results showed that Et-Tol-DAPhen ligands can coordinate strongly with metal ions, and the coordination moieties remain intact under CID conditions. Natural bond orbital (NBO), molecular electrostatic potential (MEP), electron localization function (ELF), atoms in molecules (AIM) and molecular orbital (MO) analyses indicated that the metal–ligand bonds of the actinide complexes exhibited more covalent character than those of the lanthanide complexes. In addition, according to thermodynamic analysis, the stable cationic M–L complexes in acetonitrile are found to be in good agreement with the ESI-MS results.
Co-reporter:Juan Luo, Cong-Zhi Wang, Jian-Hui Lan, Qun-Yan Wu, Yu-Liang Zhao, Zhi-Fang Chai, Chang-Ming Nie and Wei-Qun Shi
Dalton Transactions 2015 vol. 44(Issue 7) pp:3227-3236
Publication Date(Web):24 Dec 2014
DOI:10.1039/C4DT03321C
Actinide separation in spent nuclear fuel reprocessing is essential for the closed nuclear fuel cycle. Organophosphorus reagents have been found to exhibit strong affinities for actinides in experiments. In this work, the extraction complexes of AnO2n+ (An = U, Np; n = 1, 2) with the traditional organophosphorus ligand HDEHP (di-(2-ethylhexyl)phosphoric acid) have been investigated using density functional theory together with scalar-relativistic effective core potentials (ECPs) for actinide elements. According to our calculations, the HDEHP dimer prefers to act as a bidentate ligand in most of the studied complexes. HDEHP ligands show a higher extraction ability for An(VI) over An(V), and the formation of Np(VI) complexes is slightly more favorable than those of U(VI) analogues, which is mainly attributed to the stronger donor–acceptor interaction in Np(VI) complexes. The intramolecular hydrogen bonds play a significant role in the stability of the 1:1 type complexes AnO2(HL)2(NO3)2 (L = DEHP−). Moreover, AnO2(HL)2(NO3)2 are the most stable species in nitrate-rich acid solutions, while at low nitric acid concentrations, the complexing reaction of AnO2(H2O)52+ + 2(HL)2 → AnO2(HL2)2 + 2H+ + 5H2O is probably the dominant reaction in the extraction process. Our results can help to understand the speciation of actinyl complexes in real solvent extraction of actinides with HDEHP at the molecular level.
Co-reporter:Li-Xia Luo, Ya-Lan Liu, Ning Liu, Kui Liu, Li-Yong Yuan, Zhi-Fang Chai and Wei-Qun Shi
RSC Advances 2015 vol. 5(Issue 85) pp:69134-69142
Publication Date(Web):29 Jul 2015
DOI:10.1039/C5RA11708A
This work presents the electroreduction of Tb(III) ions, and formation mechanisms of Al–Tb alloys in molten chlorides by applying different types of cathodes: Mo, Al and Al-coated Mo. First, Tb(III) ions were successfully produced by the chlorination of Tb4O7 with AlCl3 in this work. Next, the mechanisms of electrode reactions were determined by various electrochemical techniques, such as cyclic voltammetry (CV), square wave voltammetry (SWV), chronopotentiometry (CP) and open circuit chronopotentiometry (OCP). On the Mo electrode, the reduction of Tb(III) to Tb(0) was determined to be reversible and a one-step process with three electrons exchanged, which was mainly controlled by the mass transport process of linear diffusion of Tb(III) in a chloride melt. In addition, the diffusion coefficient of Tb(III) was calculated to be (2.29 ± 0.01) ×10−5 cm2 s−1 by the Sand equation. According to electrochemical investigations, it was clear that Al–Tb alloy formation was feasible on both solid aluminum and Al-coated molybdenum electrodes. Three redox signals corresponding to the formation and dissolution of different kinds of Al–Tb intermetallic compounds were observed on the Al-coated Mo electrode, whereas only one redox signal was detected on the solid Al electrode. Finally, deposited Al–Tb alloy samples were prepared by potentiostatic electrolysis and characterized by scanning electronic microscopy coupled with energy dispersive spectrum (SEM-EDS) and X-ray diffraction (XRD). It was found that the intermetallic compound Al2Tb was formed by potentiostatic electrolysis at a potential of −1.6 V and at a temperature of 803 K. When the deposition temperature was elevated to 903 K, the intermetallic compound Al3Tb was then obtained by potentiostatic electrolysis.
Co-reporter:Qun-Yan Wu, Jian-Hui Lan, Cong-Zhi Wang, Yu-Liang Zhao, Zhi-Fang Chai, and Wei-Qun Shi
The Journal of Physical Chemistry A 2015 Volume 119(Issue 5) pp:922-930
Publication Date(Web):January 13, 2015
DOI:10.1021/jp512950j
The compound L–U–N [L = [N(CH2CH2NSiPri3)3]3–, Pri = CH(CH3)2] containing a terminal U–N triple bond has been synthesized and isolated successfully in experiments. To investigate the trend in the bonding nature of its pnictogen analogues, we have studied the L–U–E (E = N, P, As, Sb, and Bi) complexes using the scalar relativistic density functional theory. The terminal U–E multiple bond length increases in the order of U–N ≪ U–P < U–As < U–Sb < U–Bi, which can be supported by the hard and soft acids and bases (HSAB) theory. The U–E bond length, molecular orbital (MO), and natural bond orbital (NBO) reveal that the terminal U–E bonds should be genuine triple bonds containing one σ- and two π-bonding orbitals. Quantum theory of atoms in molecules (QTAIM) topological analysis and the electron localization function (ELF) suggest that the terminal U–E bond possesses covalent character and the covalency of U–E bonds decrease sharply when the terminal atom becomes heavier. This work presents a comparison about the bonding characteristic between the terminal U≡N bond and its heavier pnictogen (P, As, Sb, and Bi) analogues. It is expected that this work would shed light on the evaluation of the amount of 5f orbital participation in multiple bonds and further facilitate our deeper understanding of f-block elements.
Co-reporter:Jian-Hui Lan, Cong-Zhi Wang, Qun-Yan Wu, Shu-Ao Wang, Yi-Xiao Feng, Yu-Liang Zhao, Zhi-Fang Chai, and Wei-Qun Shi
The Journal of Physical Chemistry A 2015 Volume 119(Issue 34) pp:9178-9188
Publication Date(Web):July 30, 2015
DOI:10.1021/acs.jpca.5b06370
Actinyl(VI, V) (An = U, Np and Pu) complexes of the recently reported hybrid macrocycle, cyclo[1]furan[1]pyridine[4]pyrrole (denoted as H4L), have been studied using density functional theory in combination with the small-core scalar-relativistic effective core potentials and corresponding (14s13p10d8f6g)/[ 10s9p5d4f3g] basis sets in the segmented contraction scheme. On the basis of our calculations, the pyrrole nitrogen atoms that possess the shortest An-L bonds and strongest basicity are the main donor atoms that contribute to the formation of actinyl(VI, V) complexes. The natural population analysis (NPA) suggests higher ligand-to-actinyl charge transfer in the actinyl(VI) complexes than in their actinyl(V) analogues, which account for the higher decomposition energies of the former. A significant actinide-to-ligand spin density delocalization in the uranyl(V) and neptunyl(V) complexes was observed owing to the redistribution of spin density caused by complexation. A thermodynamic analysis indicates that the formation of the actinyl(VI, V) complexes are exothermic reactions in CH2Cl2 solvent, where the uranyl cations show the highest selectivity. In aqueous solution containing chloride ions, for complexing with macrocycle H4L, the plutonyl(VI) and uranyl(V) cations possess the highest selectivity among actinyl(VI) and (V) cations, respectively. This work can shed light on the design of macrocycle complexes for actinide recognition and extraction in the future.
Co-reporter:Yujuan Zhang;Jianhui Lan;Qunyan Wu;Congzhi Wang;Tao Bo
Science China Chemistry 2015 Volume 58( Issue 12) pp:1891-1897
Publication Date(Web):2015 December
DOI:10.1007/s11426-015-5441-7
The in-pile performance of ceramic fuels is significantly affected by the fission products. In this work, we have performed first-principles density functional theoretical calculations to study the interaction between metallic fission products (barium and zirconium) and the uranium dinitride UN2 matrix. The thermodynamic properties and bonding nature of Ba and Zr atoms in different incorporation configurations indicate that Zr is more soluble in UN2 matrix than Ba. With increasing the concentration of the impurity atoms, Zr-doped UN2 exhibits a slight tendency to contract, while Ba-doped UN2 tends to swell. Based on the competition between steric effect and chemical interaction, various incorporation trends for Ba and Zr in UN2 as well as in UN have been understood.
Co-reporter:Yu-Juan Zhang
The Journal of Physical Chemistry C 2015 Volume 119(Issue 11) pp:5783-5789
Publication Date(Web):March 4, 2015
DOI:10.1021/jp510219a
The incorporation and diffusion behaviors of Xe in uranium mononitride (UN) have been studied using first-principles density functional theory calculations. The incorporation and binding energies of Xe located at different sites are calculated. Because of strain relief related to moving Xe atom from highly strained interstitial site into the large steric vacancy site, a stronger binding energy between the incorporated Xe and the large steric vacancy forms. Using ab initio molecular dynamics simulations and climbing-image nudged elastic band calculations, we found that the activation barrier of interstitial Xe in UN in the “kick-out” diffusion mechanism is lower than that in the direct interstitial mechanism, and the net Xe diffusion occurs with vacancies mediated; that is, once an interstitial Xe atom is trapped in a U vacancy site, it will be immobile without other uranium vacancies mediated.
Co-reporter:Wei-Qun Shi;Li-Yong Yuan;Cong-Zhi Wang;Lin Wang;Lei Mei;Cheng-Liang Xiao;Li Zhang;Zi-Jie Li;Yu-Liang Zhao;Zhi-Fang Chai
Advanced Materials 2014 Volume 26( Issue 46) pp:7807-7848
Publication Date(Web):
DOI:10.1002/adma.201304323
Synchrotron radiation (SR) based techniques have been utilized with increasing frequency in the past decade to explore the brilliant and challenging sciences of actinide-based materials. This trend is partially driven by the basic needs for multi-scale actinide speciation and bonding information and also the realistic needs for nuclear energy research. In this review, recent research progresses on actinide related materials by means of various SR techniques were selectively highlighted and summarized, with the emphasis on X-ray absorption spectroscopy, X-ray diffraction and scattering spectroscopy, which are powerful tools to characterize actinide materials. In addition, advanced SR techniques for exploring future advanced nuclear fuel cycles dealing with actinides are illustrated as well.
Co-reporter:Li-Yong Yuan, Zhi-Qiang Bai, Ran Zhao, Ya-Lan Liu, Zi-Jie Li, Sheng-Qi Chu, Li-Rong Zheng, Jing Zhang, Yu-Liang Zhao, Zhi-Fang Chai, and Wei-Qun Shi
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 7) pp:4786
Publication Date(Web):March 12, 2014
DOI:10.1021/am405584h
The potential industrial application of thorium (Th), as well as the environmental and human healthy problems caused by thorium, promotes the development of reliable methods for the separation and removal of Th(IV) from environmental and geological samples. Herein, the phosphonate-amino bifunctionalized mesoporous silica (PAMS) was fabricated by a one-step self-assembly approach for enhancing Th(IV) uptake from aqueous solution. The synthesized sorbent was found to possess ordered mesoporous structures with uniform pore diameter and large surface area, characterized by SEM, XRD, and N2 sorption/desorption measurements. The enhancement of Th(IV) uptake by PAMS was achieved by coupling of an access mechanism to a complexation mechanism, and the sorption can be optimized by adjusting the coverage of the functional groups in the PAMS sorbent. The systemic study on Th(IV) sorption/desorption by using one coverage of PAMS (PAMS12) shows that the Th(IV) sorption by PAMS is fast with equilibrium time of less than 1 h, and the sorption capacity is more than 160 mg/g at a relatively low pH. The sorption isotherm has been successfully modeled by the Langmuir isotherm and D-R isotherm, which reveals a monolayer homogeneous chemisorption of Th(IV) in PAMS. The Th(IV) sorption by PAMS is pH dependent but ionic strength independent. In addition, the sorbed Th(IV) can be completely desorbed using 0.2 mol/L or more concentrated nitric acid solution. The sorption test performed in the solution containing a range of competing metal ions suggests that the PAMS sorbent has a desirable selectivity for Th(IV) ions.Keywords: amino; bifunctionality; mesoporous silica; phosphonate; sorption; thorium;
Co-reporter:Lei Mei, Qun-yan Wu, Cai-ming Liu, Yu-liang Zhao, Zhi-fang Chai and Wei-qun Shi
Chemical Communications 2014 vol. 50(Issue 27) pp:3612-3615
Publication Date(Web):11 Feb 2014
DOI:10.1039/C4CC00690A
In situ assembly of a cucurbituril-based pseudorotaxane and a uranyl nitrate precursor under hydrothermal conditions affords the first actinide polyrotaxane with a unique ‘dragon-like’ twist, which is induced by the specific coordination pattern of uranium and stabilized by hydrogen bonding between the η1-mode carboxylate group and adjacent methylene moieties of CB[6].
Co-reporter:Kui Liu, Ya-Lan Liu, Li-Yong Yuan, Hui He, Zhi-Yuan Yang, Xiu-Liang Zhao, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2014 Volume 129() pp:401-409
Publication Date(Web):20 May 2014
DOI:10.1016/j.electacta.2014.02.136
This work firstly presents an electrochemical study of samarium extraction from Sm2O3 in the LiCl–KCl–AlCl3 melts. Gibbs energy calculation shows that AlCl3 can favorably chloridize Sm2O3 and release Sm3+ ions under this condition. The electrochemical behaviors of Al3+, Sm3+ and the mechanisms of alloy formation were investigated using a series of electrochemical techniques on a molybdenum electrode. Two typical signals corresponding to different kinds of Sm–Al alloys were observed in the cyclic voltammetry and square wave voltammetry. The transformation process from one AlxSmy biphasic phase to another was revealed by open circuit chronopotentiometry. The Sm-Al alloy samples were prepared by potentiostatic and galvanostatic electrolysis on an aluminium electrode. SEM-EDS and XRD analysis demonstrated that a layer of SmAl3 can be formed by potentiostatic electrolyses, whereas two kinds of intermetallic compounds of SmAl4 and SmAl3 can be formed by galvanostatic electrolysis. In addition, the electroextraction of samarium by co-reduction with Al3+ on the aluminium electrode has been performed with extraction efficiency of 88.7% for potentiostatic electrolysis and 94% for galvanostatic electrolysis, respectively.
Co-reporter:Ling-Ling Su, Kui Liu, Ya-Lan Liu, Lu Wang, Li-Yong Yuan, Lin Wang, Zi-Jie Li, Xiu-Liang Zhao, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2014 Volume 147() pp:87-95
Publication Date(Web):20 November 2014
DOI:10.1016/j.electacta.2014.09.095
In this work, the electrochemical behaviors of Dy(III) and its co-reduction with Al(III) on an inert tungsten electrode was investigated in LiCl-KCl molten salts at the temperature of 773 K by using cyclic voltammetry (CV), chronopotentiometry (CP) and square wave voltammetry (SWV) techniques. The results showed that the reduction of Dy(III) ions in LiCl-KCl salts is a reversible diffusion controlled process through a one-step reaction: Dy(III) + 3e− ↔ Dy(0). The diffusion coefficient of Dy(III) ions was calculated by both the CV and CP methods. Furthermore, the co-reduction of Al(III) and Dy(III) ions on the inert tungsten electrode allows Dy(III) ions to be reduced at a more positive potential through forming Al-Dy alloys. The concentration ratio of Al(III) cations to Dy(III) cations has a large impact on the formation of Al-Dy alloys. In a Dy(III) ion rich system, three signals attributed to the formation of Al-Dy intermetallic compounds were observed in CV and SWV analyses, while only two signals corresponding to Al-Dy intermetallic compounds were observed in the Dy(III) ion poor system. Potentiostatic and galvanostatic electrolyses performed on an aluminum electrode identified the co-reduction by the formation of one (Al3Dy) and two Al-Dy alloys (Al3Dy, AlDy), respectively. Finally, the electrolysis products were characterized by the Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) analyses.
Co-reporter:Lu Wang, Ya-Lan Liu, Kui Liu, Shuang-Ling Tang, Li-Yong Yuan, Ling-Ling Su, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2014 Volume 147() pp:385-391
Publication Date(Web):20 November 2014
DOI:10.1016/j.electacta.2014.08.113
This work concerns the co-reduction behaviors of Ce(III) with Al(III) ions and electrochemical extraction of cerium from cerium dioxide in molten LiCl-KCl at the temperature of 773K. Cyclic voltammetry (CV), square wave voltammetry (SWV), chronopotentiometry (CP), and open circuit chronopotentiometry (OCP) techniques were employed to investigate the electrochemical behaviors of Ce(III) and Al(III) ions on molybdenum (Mo) electrode. The results revealed Ce(III) and Al(III) cations can be co-reduced at the surface of the Mo electrode by forming different kinds of Ce-Al alloys. Finally, potentiostatic electrolysis at different deposition potentials on Al plate electrodes was also performed to prepare Ce-Al alloys. The deposition products were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS). It was found that only one intermetallic compound (Al11Ce3) could be formed at the deposition potential of -1.6 V and two intermetallic compounds (Al11Ce3 and Al3Ce) could be formed at the potential of -1.9 V. When the deposition potential was negative than -2.1 V, cerium-rich alloy (AlCe) could be obtained on the surface of the Al electrode.
Co-reporter:Kui Liu, Ya-Lan Liu, Li-Yong Yuan, Xiu-Liang Zhao, Hui He, Guo-An Ye, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2014 Volume 116() pp:434-441
Publication Date(Web):10 January 2014
DOI:10.1016/j.electacta.2013.11.093
This work presents an electrochemical study of Er3+ and Al3+ in the LiCl-KCl-AlCl3-Er2O3 melts at 773 K. Gibbs energy calculation shows that AlCl3 can favorably chloridize Er2O3 and release Er3+ ions under this condition. Cyclic voltammetry, square wave voltammetry, chronopotentiometry and open-circuit chronopotentiometry were applied using a molybdenum electrode to investigate the reduction behavior of Er3+ and Al3+ and to identify the Er-Al alloys. A series of redox signals corresponding to different kinds of Er-Al alloys were revealed. Potentiostatic and gavanostastic electrolysis were both conducted on an aluminium electrode to prepare the Er-Al alloys. The obtained deposits were charaterized by SEM-EDS and XRD. A layer of ErAl3 was obtained by potentiostatic electrolysis, whereas two kinds of intermetallic compounds of ErAl3 and ErAl2 were formed by galvanostatic electrolysis.
Co-reporter:Cheng-Liang Xiao, Qun-Yan Wu, Cong-Zhi Wang, Yu-Liang Zhao, Zhi-Fang Chai, and Wei-Qun Shi
Inorganic Chemistry 2014 Volume 53(Issue 20) pp:10846-10853
Publication Date(Web):September 30, 2014
DOI:10.1021/ic500816z
Co-reporter:Qun-Yan Wu, Cong-Zhi Wang, Jian-Hui Lan, Cheng-Liang Xiao, Xiang-Ke Wang, Yu-Liang Zhao, Zhi-Fang Chai, and Wei-Qun Shi
Inorganic Chemistry 2014 Volume 53(Issue 18) pp:9607-9614
Publication Date(Web):September 3, 2014
DOI:10.1021/ic501006p
A series of actinide (An) species of L-An-N compounds [An = Pa–Pu, L = [N(CH2CH2NSiPri3)3]3–, Pri = CH(CH3)2] have been investigated using scalar relativistic density functional theory (DFT) without considering spin–orbit coupling effects. The ground state geometric and electronic structures and natural bond orbital (NBO) analysis of actinide compounds were studied systematically in neutral and anionic forms. It was found that with increasing actinide atomic number, the bond length of terminal multiple An–N1 bond decreases, in accordance with the actinide contraction. The Mayer bond order of An–N1 decreases gradually from An = Pa to Pu, which indicates a decrease in bond strength. The terminal multiple bond for L–An–N compounds contains one σ and two π molecular orbitals, and the contributions of the 6d orbital to covalency are larger in magnitude than the 5f orbital based on NBO analysis and topological analysis of electron density. This work may help in understanding of the bonding nature of An–N multiple bonds and elucidating the trends and electronic structure changes across the actinide series. It can also shed light on the construction of novel An–N multiple bonds.
Co-reporter:Cheng-Liang Xiao, Cong-Zhi Wang, Li-Yong Yuan, Bin Li, Hui He, Shuao Wang, Yu-Liang Zhao, Zhi-Fang Chai, and Wei-Qun Shi
Inorganic Chemistry 2014 Volume 53(Issue 3) pp:1712-1720
Publication Date(Web):January 10, 2014
DOI:10.1021/ic402784c
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.
Co-reporter:Cong-Zhi Wang, Jian-Hui Lan, Qun-Yan Wu, Qiong Luo, Yu-Liang Zhao, Xiang-Ke Wang, Zhi-Fang Chai, and Wei-Qun Shi
Inorganic Chemistry 2014 Volume 53(Issue 18) pp:9466-9476
Publication Date(Web):September 4, 2014
DOI:10.1021/ic500202g
Recovery of uranium from seawater is extremely challenging but important for the persistent development of nuclear energy, and thus exploring the coordination structures and bonding nature of uranyl complexes becomes essential for designing highly efficient uranium adsorbents. In this work, the interactions of uranium and a series of adsorbents with various well-known functional groups including amidoximate (AO–), carboxyl (Ac–), glutarimidedioximate (HA–), and bifunctional AO–/Ac–, HA–/Ac– on different alkyl chains (R′═CH3, R″═C13H26) were systematically studied by quantum chemical calculations. For all the uranyl complexes, the monodentate and η2 coordination are the main binding modes for the AO– groups, while Ac– groups act as monodentate and bidentate ligands. Amidoximes can also form cyclic imide dioximes (H2A), which coordinate to UO22+ as tridentate ligands. Kinetic analysis of the model displacement reaction confirms the rate-determining step in the extraction process, that is, the complexing of uranyl by amidoxime group coupled with the dissociation of the carbonate group from the uranyl tricarbonate complex [UO2(CO3)3]4–. Complexing species with AO– groups show higher binding energies than the analogues with Ac– groups. However, the obtained uranyl complexes with Ac– seem to be more favorable according to reactions with [UO2(CO3)3]4– as reactant, which may be due to the higher stability of HAO compared to HAc. This is also the reason that species with mixed functional group AO–/Ac– are more stable than those with monoligand. Thus, as reported in the literature, the adsorbability of uranium can be improved by the synergistic effects of amidoxime and carboxyl groups.
Co-reporter:Lin Wang, Ran Zhao, Xin-wei Wang, Lei Mei, Li-yong Yuan, Shu-ao Wang, Zhi-fang Chai and Wei-qun Shi
CrystEngComm 2014 vol. 16(Issue 45) pp:10469-10475
Publication Date(Web):22 Sep 2014
DOI:10.1039/C4CE01731E
We report a facile method to synthesize monodisperse, uniform and size-controllable thorium dioxide nanoparticles via a hydrothermal precursor synthesis and a subsequent calcination treatment. Highly uniform spherical precursor nanoparticles with a tunable diameter of 38–274 nm and monodisperse irregular precursor nanoparticles with a size range of 20–45 nm can be successfully synthesized using thorium nitrate pentahydrate, urea and glycerol as the metal source, nucleation agent, and size-controlling agent, respectively. The chemical composition, growth process, and size control of the precursor nanoparticles have been systematically investigated, and a probable formation mechanism of these nanoparticles was also proposed. Calcination of precursor nanoparticles at 800 °C leads to the formation of uniform thorium dioxide nanoparticles without any morphological deformation. Furthermore, the size and shape effects of thorium dioxide nanoparticles on the uptake of dye molecules have been studied. The corresponding adsorption behaviors of as-prepared samples can be elucidated very well by the nitrogen adsorption–desorption analysis.
Co-reporter:Ran Zhao, Lin Wang, Zhan-Jun Gu, Li-Yong Yuan, Cheng-Liang Xiao, Yu-Liang Zhao, Zhi-Fang Chai and Wei-Qun Shi
CrystEngComm 2014 vol. 16(Issue 13) pp:2645-2651
Publication Date(Web):06 Jan 2014
DOI:10.1039/C3CE42140F
Spherical UO2 nanoparticles with an average diameter varying from 30 to 250 nm and U3O8 nanocuboids with a width of 400 nm and a length of 1 μm have been successfully synthesized just by a simply additive-free hydrothermal synthesis method. To selectively obtain the phase-pure U3O8 and UO2 nanoparticles, the experimental conditions, such as the solution pH and temperature as well as the concentration of hydrazine, have been established and optimized. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In order to investigate the growth mechanism of the uranium oxide nanoparticles, XRD, SEM and Fourier transform infrared (FT-IR) spectrum measurements were carried out for the precursors prepared at different pH and hydrothermal time. The crucial factor for tunable fabrication of uranium oxide nanoparticles could come from the different reducing ability of hydrazine at various solution pH.
Co-reporter:Cheng-Liang Xiao, Qun-Yan Wu, Lei Mei, Li-Yong Yuan, Cong-Zhi Wang, Yu-Liang Zhao, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2014 vol. 43(Issue 33) pp:12470-12473
Publication Date(Web):26 Jun 2014
DOI:10.1039/C4DT01489H
A preorganized tetradentate phenanthroline-derived amide ligand, N,N′-diethyl-N,N′-ditolyl-2,9-dicarboxamide-1,10-phenanthroline (Et-Tol-DAPhen), was found to show high selectivity towards small copper ions, which might be due to the change of the coordination mechanism from tetradentate to terdentate mode.
Co-reporter:Cong-Zhi Wang, Jian-Hui Lan, Qun-Yan Wu, Yu-Liang Zhao, Xiang-Ke Wang, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2014 vol. 43(Issue 23) pp:8713-8720
Publication Date(Web):09 Apr 2014
DOI:10.1039/C4DT00032C
At present, designing novel ligands for efficient actinide extraction in spent nuclear fuel reprocessing is extremely challenging due to the complicated chemical behaviors of actinides, the similar chemical properties of minor actinides (MA) and lanthanides, and the vulnerability of organic ligands in acidic radioactive solutions. In this work, a quantum chemical study on Am(III), Cm(III) and Eu(III) complexes with N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and N,N′-dimethyl-N,N′-diheptyl-3-oxapentanediamide (DMDHOPDA) has been carried out to explore the extraction behaviors of trivalent actinides (An) and lanthanides (Ln) with diglycolamides from acidic media. It has been found that in the 1:1 (ligand:metal) and 2:1 stoichiometric complexes, the carbonyl oxygen atoms have stronger coordination ability than the ether oxygen atoms, and the interactions between metal cations and organic ligands are substantially ionic. The neutral ML(NO3)3 (M = Am, Cm, Eu) complexes seem to be the most favorable species in the extraction process, and the predicted relative selectivities are in agreement with experimental results, i.e., the diglycolamide ligands have slightly higher selectivity for Am(III) over Eu(III). Such a thermodynamical priority is probably caused by the higher stabilities of Eu(III) hydration species and Eu(III)–L complexes in aqueous solution compared to their analogues. In addition, our thermodynamic analysis from water to organic medium confirms that DMDHOPDA has higher extraction ability for the trivalent actinides and lanthanides than TODGA, which may be due to the steric hindrance of the bulky alkyl groups of TODGA ligands. This work might provide an insight into understanding the origin of the actinide selectivity and a theoretical basis for designing highly efficient extractants for actinide separation.
Co-reporter:Lin Wang;Ran Zhao;Zhan-jun Gu;Yu-liang Zhao;Zhi-fang Chai
European Journal of Inorganic Chemistry 2014 Volume 2014( Issue 7) pp:1158-1164
Publication Date(Web):
DOI:10.1002/ejic.201301634
Abstract
Actinide nanomaterials have great potential for application in the fabrication of nuclear fuels and spent fuel reprocessing in advanced nuclear energy systems. In this work, we used track-etched nanoporous membranes as hard templates to synthesize uranium-based nanomaterials with new structures by electrodeposition. Through electrochemical behavior investigations and subsequent product characterization, the chemical compositions of the deposition product has been confirmed to be uranyl hydroxide. More importantly, accurate control of the morphologies of the deposition product (i.e., nanowires and nanotubes) could be achieved by carefully adjusting the growth parameters such as deposition time and current density. The preferred morphology of the electrodeposition product was nanowires when a low current density was applied, whereas nanotubes could be formed only when a high current density and a short deposition time were both applied. The formation of nanotubes is attributed to the hydrogen bubbles generated by water electrolysis under the overpotential electroreduction conditions. Additionally, we transformed the main chemical composition of the deposition products from uranyl hydroxide to triuranium octoxide by calcination, and SEM results showed that the morphologies of the nanowires and nanotubes were very well maintained after the calcination. Our work provides a useful protocol for the synthesis of one-dimensional uranium-based nanomaterials.
Co-reporter:Ran Zhao, Lin Wang, Zhi-Fang Chai and Wei-Qun Shi
RSC Advances 2014 vol. 4(Issue 94) pp:52209-52214
Publication Date(Web):10 Oct 2014
DOI:10.1039/C4RA07466A
In this work, ThO2 nanostructures with various morphologies are synthesized through a hydrothermal approach. The influences of some experimental parameters, such as the concentration of hexamethylenetetramine (HMTA), the amount of sodium dodecyl sulfate (SDS) and the hydrothermal temperature, on the synthesis and morphologies of ThO2 nanostructures were systematically investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results showed that ThO2 nanospheres with a particle size of 59 ± 9 nm could be synthesized at a molar ratio of Th4+/HMTA of 0.3 under the reaction temperature of 100 °C. Adding SDS could adjust the diameter of ThO2 nanospheres from 240 to 71 nm while keeping other parameters constant. Furthermore, nanoparticles and the aggregated nanostructures of ThO2 could be obtained by varying the concentration of HMTA and the amount of SDS. The possible formation mechanism of various ThO2 nanostructures was also proposed.
Co-reporter:Zhi-Qiang Bai, Zi-Jie Li, Cong-Zhi Wang, Li-Yong Yuan, Zhi-Rong Liu, Jing Zhang, Li-Rong Zheng, Yu-Liang Zhao, Zhi-Fang Chai and Wei-Qun Shi
RSC Advances 2014 vol. 4(Issue 7) pp:3340-3347
Publication Date(Web):25 Oct 2013
DOI:10.1039/C3RA45938A
Graphene oxide (GO) has been receiving increasing research efforts in recent years because of its wide applications in various scientific fields. In this work the sorption of Th(IV) onto graphene oxide (GO) was studied using a batch method under ambient conditions. The sorption kinetics were found to be fast and fitted the pseudo-second-order model very well, with an equilibrium time of about 10 min. The sorption is strongly dependent on the solution pH but independent of the ionic strength of the solution. The maximum sorption capacity of as high as 214.6 mg g−1 can be achieved at pH 2.60 ± 0.05, and Th(IV) can be desorbed readily from the GO with 1.0 M HNO3. The thermodynamic investigations revealed that the sorption of Th(IV) on the GO was an endothermic and spontaneous process. The Scanning Electron Microscopy (SEM) results indicated obvious surface morphology changes of the GO induced by Th(IV) sorption. Furthermore, the interaction mechanism of Th(IV) and the GO was investigated by infrared (IR) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy combined with density functional theory (DFT) calculations. The results of EXAFS indicated that Th(IV) was bonded to ∼8 or 9 oxygen atoms and the average bond length of Th–O was estimated to be ∼2.45 Å in the first coordination shell. The DFT calculations further confirm the rationality of experimental and the EXAFS results. This work demonstrates the tremendous potential opportunities offered by GO in pre-concentration and removal of thorium and other tetravalent actinides for the recovery and remediation of the environment.
Co-reporter:Tao Bo, Jian-Hui Lan, Yao-Lin Zhao, Yu-Juan Zhang, Chao-Hui He, Zhi-Fang Chai, Wei-Qun Shi
Journal of Nuclear Materials 2014 Volume 454(1–3) pp:446-454
Publication Date(Web):November 2014
DOI:10.1016/j.jnucmat.2014.09.001
The adsorption and dissociation behaviors of water molecule on the UO2 (1 1 1), (1 1 0) and (1 0 0) surfaces were investigated using first-principles methods within the DFT+U framework. For a single water molecule at 1/4 ML coverage, the molecular adsorption exhibits comparable adsorption energies with the dissociative adsorption on the (1 1 1) surface, while it is far less stable than the dissociative adsorption on the (1 1 0) and (1 0 0) surfaces. We find that the adsorbed molecular and dissociative water tend to cluster on low-index UO2 surfaces by forming hydrogen-bond networks. The adsorption stability of water depends on the synergistic effect of hydrogen bonding interaction and steric effect between adsorbates. The mixed adsorption configuration of molecular and dissociative water in 1:1 mol ratio is found to be thermally more stable on the UO2 (1 1 1) and (1 1 0) surfaces.
Co-reporter:Yu-Juan Zhang ; Jian-Hui Lan ; Tao Bo ; Cong-Zhi Wang ; Zhi-Fang Chai
The Journal of Physical Chemistry C 2014 Volume 118(Issue 26) pp:14579-14585
Publication Date(Web):June 12, 2014
DOI:10.1021/jp501863y
Barium and zirconium solution behaviors in antiferromagnetic uranium mononitride (UN) have been studied based on first-principles density functional theory. By calculating the incorporation and solution energies in UN, it is found that the most favorable solution sites are U vacancies for both Ba and Zr, and Zr is more soluble than Ba. The volume of the Ba-doped system keeps expanding with increasing Ba doping concentration, whereas that of the Zr-doped system changes from swelling to contraction with increasing Zr doping concentration. This phenomenon may result from the difference of these two elements in atom radius and coordination mechanism. Furthermore, the solution energies of metallic and nitride phases of Ba and Zr indicate that both phases of Ba are insoluble in the UN matrix, whereas the metallic phase of Zr is insoluble, and its nitride ZrN is soluble in the UN matrix.
Co-reporter:Tao Bo ; Jian-Hui Lan ; Cong-Zhi Wang ; Yao-Lin Zhao ; Chao-Hui He ; Yu-Juan Zhang ; Zhi-Fang Chai
The Journal of Physical Chemistry C 2014 Volume 118(Issue 38) pp:21935-21944
Publication Date(Web):September 3, 2014
DOI:10.1021/jp503614f
Molecular and dissociative adsorption behavior of H2O along with the accompanying H2 formation mechanism on the UO2 (111) and (110) surfaces have been investigated by using DFT+U calculations. According to our calculations, the higher stability of the (111) surface leads to higher oxygen vacancy formation energy compared to the (110) surface. On the stoichiometric (111) and (110) surfaces, the first hydrogen atom of water molecule can dissociate readily with very small or no energy barrier. On the contrary, dissociation of the second one becomes the rate-determining step, and water-catalysis leads to the decrease of energy barrier from 0.92 to 0.70 eV and from 2.36 to 1.21 eV on the stoichiometric (111) and (110) surfaces, respectively. H2 formation resulting from water dissociation may undergo two pathways in the presence of surface oxygen vacancy on the reduced UO2 (111) surface. One is characterized by direct combination of two hydrogen atoms of one water molecule, and the other is characterized by dissociation of the first hydrogen atom and its combination with a neighboring surface hydrogen atom. The above two formation pathways possess the energy barriers of 0.56 and 0.53 eV, corresponding to the large reaction energies of −2.62 and −2.64 eV, respectively.
Co-reporter:LiYong Yuan;Man Sun;XiangHong Liao;YuLiang Zhao;ZhiFang Chai
Science China Chemistry 2014 Volume 57( Issue 11) pp:1432-1438
Publication Date(Web):2014 November
DOI:10.1007/s11426-014-5194-8
The unique physical and chemical properties of room-temperature ionic liquids (RTILs) have recently received increasing attention as solvent alternatives for possible application in the field of nuclear industry, particularly in liquid-liquid separations of radioactive nuclides. We investigated solvent extraction of U(VI) from aqueous solutions into a commonly used ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][NTf2]) using trioctylphosphine oxide (TOPO) as an extractant. The effects of contact time, TOPO concentration, acidity, and nitrate ions on the U(VI) extraction are discussed in detail. The extraction mechanism was proposed based on slope analysis and UV-Vis measurement. The results clearly show that TOPO/[C4mim][NTf2] provides a highly efficient extraction of U(VI) from aqueous solution under near-neutral conditions. When the TOPO concentration was 10 mmol/L, the extraction of 1 mmol/L U(VI) was almost complete (> 97%). Both the extraction efficiency and distribution coefficient were much larger than in conventional organic solvents such as dichloromethane. Slope analysis confirmed that three TOPO molecules in [C4mim][NTf2] bound with one U(VI) ion and one nitrate ion was also involved in the complexation and formed the final extracted species of [UO2(NO3)(TOPO)3]+. Such a complex suggests that extraction occurs by a cation-exchange mode, which was subsequently evidenced by the fact that the concentration of C4mim+ in the aqueous phase increased linearly with the extraction percent of U(VI) recorded by UV-Vis measurement.
Co-reporter:ChengLiang Xiao;QunYan Wu;CongZhi Wang;YuLiang Zhao
Science China Chemistry 2014 Volume 57( Issue 11) pp:1439-1448
Publication Date(Web):2014 November
DOI:10.1007/s11426-014-5215-7
To design novel phenanthroline-derived soft ligands for selectively separating minor actinides from lanthanides, four tetradentate phenanthroline-derived heterocyclic ligands (BTPhen, BPyPhen, BPzPhen, and BBizPhen) were constructed and their complexation behaviors with Am(III) and Eu(III) were systematically investigated by density functional theory (DFT) coupled with relativistic small-core pseudopotential. In all the 1:1-type species, the metal ion is in the center of the cavity and coordinates with two nitrogen atoms (N1 and N1′) of the phenanthroline skeleton and the other two nitrogen atoms (N2 and N2′) of the auxiliary groups. The bond lengths of Am-N are comparable to or even shorter than those of Eu-N bonds because the ionic radii of Am(III) are larger than those of Eu(III). Additionally, the negative ΔΔGAm/Eu value for the reaction of [M(H2O)4(NO3)3] + L → ML(NO3)3 + 4H2O indicates that the complexation reaction of Am(III) is more energetically favorable than that of Eu(III); this can be considered as an important design criterion to screen phenanthroline-derived ligands for MA(III) extraction. According to this criterion, the selectivity of tetradentate phenanthroline-derived ligands for separating Am(III) over Eu(III) follows the order of BTPhen > BBizPhen > BPyPhen > BPzPhen.
Co-reporter:Ya-Lan Liu, Li-Yong Yuan, Kui-Liu, Guo-An Ye, Mi-Lin Zhang, Hui He, Hong-Bin Tang, Ru-Shan Lin, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2014 120() pp: 369-378
Publication Date(Web):
DOI:10.1016/j.electacta.2013.12.081
Co-reporter:Qun-Yan Wu, Jian-Hui Lan, Cong-Zhi Wang, Yu-Liang Zhao, Zhi-Fang Chai, and Wei-Qun Shi
The Journal of Physical Chemistry A 2014 Volume 118(Issue 44) pp:10273-10280
Publication Date(Web):October 10, 2014
DOI:10.1021/jp5069945
Due to the vast application potential of graphene oxide (GO)-based materials in nuclear waste processing, it is of pivotal importance to investigate the interaction mechanisms between actinide cations such as Np(V) and Pu(IV, VI) ions and GO. In this work, we have considered four types of GOs modified by hydroxyl, carboxyl, and carbonyl groups at the edge and epoxy group on the surface, respectively. The structures, bonding nature, and binding energies of Np(V) and Pu(IV, VI) complexes with GOs have been investigated systematically using scalar-relativistic density functional theory (DFT). Geometries and harmonic frequencies suggest that Pu(IV) ions coordinate more easily with GOs compared to Np(V) and Pu(VI) ions. NBO and electron density analyses reveal that the coordination bond between Pu(IV) ions and GO possesses more covalency, whereas for Np(V) and Pu(VI) ions electrostatic interaction dominates the An–OG bond. The binding energies in aqueous solution reveal that the adsorption abilities of all GOs for actinide ions follow the order of Pu(IV) > Pu(VI) > Np(V), which is in excellent agreement with experimental observations. It is expected that this study can provide useful information for developing more efficient GO-based materials for radioactive wastewater treatment.
Co-reporter:Dr. Lin Wang;Dr. Ran Zhao;Dr. Cong-zhi Wang;Dr. Li-yong Yuan;Dr. Zhan-jun Gu;Dr. Cheng-liang Xiao;Dr. Shu-ao Wang;Dr. Xin-wei Wang; Yu-liang Zhao; Zhi-fang Chai;Dr. Wei-qun Shi
Chemistry - A European Journal 2014 Volume 20( Issue 39) pp:12655-12662
Publication Date(Web):
DOI:10.1002/chem.201403724
Abstract
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 H2O 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, U3O8, and UO3) were successfully synthesized.
Co-reporter:Qun-Yan Wu, Jian-Hui Lan, Cong-Zhi Wang, Cheng-Liang Xiao, Yu-Liang Zhao, Yue-Zhou Wei, Zhi-Fang Chai, and Wei-Qun Shi
The Journal of Physical Chemistry A 2014 Volume 118(Issue 11) pp:2149-2158
Publication Date(Web):March 4, 2014
DOI:10.1021/jp500924a
Studying the bonding nature of uranyl ion and graphene oxide (GO) is very important for understanding the mechanism of the removal of uranium from radioactive wastewater with GO-based materials. We have optimized 22 complexes between uranyl ion and GO applying density functional theory (DFT) combined with quasi-relativistic small-core pseudopotentials. The studied oxygen-containing functional groups include hydroxyl, carboxyl, amido, and dimethylformamide. It is observed that the distances between uranium atoms and oxygen atoms of GO (U–OG) are shorter in the anionic GO complexes (uranyl/GO–/2–) compared to the neutral GO ones (uranyl/GO). The formation of hydrogen bonds in the uranyl/GO–/2– complexes can enhance the binding ability of anionic GO toward uranyl ions. Furthermore, the thermodynamic calculations show that the changes of the Gibbs free energies in solution are relatively more negative for complexation reactions concerning the hydroxyl and carboxyl functionalized anionic GO complexes. Therefore, both the geometries and thermodynamic energies indicate that the binding abilities of uranyl ions toward GO modified by hydroxyl and carboxyl groups are much stronger compared to those by amido and dimethylformamide groups. This study can provide insights for designing new nanomaterials that can efficiently remove radionuclides from radioactive wastewater.
Co-reporter:Weiting Yang, Zhi-Qiang Bai, Wei-Qun Shi, Li-Yong Yuan, Tao Tian, Zhi-Fang Chai, Hao Wang and Zhong-Ming Sun
Chemical Communications 2013 vol. 49(Issue 88) pp:10415-10417
Publication Date(Web):10 Sep 2013
DOI:10.1039/C3CC44983A
MOF-76 exhibits not only high sensitivity for the detection of U(VI), but also high adsorption capacity of 298 mg g−1 at a low pH value of ∼3.0. Furthermore, the high selectivity for uranium adsorption over a series of competing metal ions is also illustrated.
Co-reporter:Ya-Lan Liu, Yong-De Yan, Wei Han, Mi-Lin Zhang, Li-Yong Yuan, Ru-Shan Lin, Guo-An Ye, Hui He, Zhi-Fang Chai, Wei-Qun Shi
Electrochimica Acta 2013 Volume 114() pp:180-188
Publication Date(Web):30 December 2013
DOI:10.1016/j.electacta.2013.09.154
In this work, ThO2 and Eu2O3 were chloridized into ThCl4 and EuCl3 by AlCl3 in LiCl–KCl melts at 800 K, forming Th(IV) and Eu(III) ions. The co-reduction of Al(III), Th(IV) and Eu(III) ions on the tungsten electrode was studied by cyclic voltammetry and square wave voltammetry techniques in different AlCl3 containing systems. The results show that in the AlCl3-rich system, the potential disparity (ΔE) between Al–Th and Al–Eu alloys deposition is about 0.8 V, which is much higher than the necessary ΔE (0.20 V) for the separation of Th(IV) from Eu(III). Subsequently, the separation of Th from the melts was carried out on the aluminium electrode by the potentiostatic electrolysis at temperature of 800 K. The products were characterized by the scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectrometer (ICP-AES). Finally, in an AlCl3-rich system by the electrolysis at −1.8 V for 50 h, the very high separation factor (SF) of Th to Eu, and the excellent separation rate of Th were calculated to be >2.0 × 104 and >99.9%, respectively.
Co-reporter:Cong-Zhi Wang, Wei-Qun Shi, Jian-Hui Lan, Yu-Liang Zhao, Yue-Zhou Wei, and Zhi-Fang Chai
Inorganic Chemistry 2013 Volume 52(Issue 19) pp:10904-10911
Publication Date(Web):September 18, 2013
DOI:10.1021/ic400895d
A series of extraction complexes of Eu(III) and Am(III) with CMPO (n-octyl(phenyl)-N,N-diisobutyl-methylcarbamoyl phosphine oxide) and its derivative Ph2CMPO (diphenyl-N,N-diisobutyl carbamoyl phosphine oxide) have been studied using density functional theory (DFT). It has been found that for the neutral complexes of 2:1 and 3:1 (ligand/metal) stoichiometry, CMPO and Ph2CMPO predominantly coordinate with metal cations through the phosphoric oxygen atoms. Eu(III) and Am(III) prefer to form the neutral 2:1 and 3:1 type complexes in nitrate-rich acid solutions, and in the extraction process the reactions of [M(NO3)(H2O)7]2+ + 2NO3– + nL → MLn(NO3)3 + 7H2O (M = Eu, Am; n = 2, 3) are the dominant complexation reactions. In addition, CMPO and Ph2CMPO show similar extractability properties. Taking into account the solvation effects, the metal–ligand binding energies are obviously decreased, i.e., the presence of solvent may have an significant effect on the extraction behavior of Eu(III) and Am(III) with CMPOs. Moreover, these CMPOs reagents have comparable extractability for Eu(III) and Am(III), confirming that these extractants have little lanthanide/actinide selectivity in acidic media.
Co-reporter:Fei Chen, Congzhi Wang, Weiqun Shi, Miao Zhang, Caiming Liu, Yuliang Zhao and Zhifang Chai
CrystEngComm 2013 vol. 15(Issue 39) pp:8041-8048
Publication Date(Web):08 Aug 2013
DOI:10.1039/C3CE41261J
Two new layered 3D uranyl fluoride complexes: Na3(UO2)2F3(OH)4(H2O)2 (1) and Cs(UO2)2F5 (2) have been prepared using the hydrothermal method and characterized via single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group C2/c [a = 15.125(3) Å, b = 6.941(1) Å, c = 11.257(2) Å, and β = 94.76(3)°] and compound 2 in the orthorhombic space group Cmcm [a = 12.149(2) Å, b = 11.862(2) Å, c = 12.366(2) Å], respectively. Both of them possess extended 3D structures. Furthermore, UVIO–alkalis (Na, Cs) interactions were observed in two compounds, which is relatively rare in U(VI) complexes. By introducing alkali ions, the layered structures can be further assembled into three-dimensional ones. Density functional theory (DFT) studies confirmed that the interactions between the alkalis and the oxygens of uranyl mainly ionic with small proportion of covalency, which results in the formation of these uranyl fluoride complexes with 3D structures.
Co-reporter:Jian-Hui Lan, Wei-Qun Shi, Li-Yong Yuan, Jun Li, Yu-Liang Zhao, Zhi-Fang Chai
Coordination Chemistry Reviews 2012 Volume 256(13–14) pp:1406-1417
Publication Date(Web):July 2012
DOI:10.1016/j.ccr.2012.04.002
The selective extraction of minor actinides(III) from the lanthanides(III) is a key step for spent fuel reprocessing. Theoretical calculations of geometries, electronic structures, coordination complexion, and thermodynamic properties of the actinides are essential for understanding the separation mechanisms and relevant reactions. This article presents a critical review of theoretical studies on actinide systems involved in the An(III)/Ln(III) separation process. We summarize various theoretical methods for electronic and molecular scale modeling and simulations of actinide coordination systems. The complexing mechanisms between metal cations and organic ligands and the strategies for the design of novel ligands for separation are discussed as well.Highlights► We review recent advances in computational modeling and simulations on the An(III)/Ln(III) separation process. ► Various theoretical methods for electronic and molecular-scale modeling and simulations of actinide systems are summarized. ► The complexation between soft-donating ligands and An(III)/Ln(III) ions are explored. ► The strategies for design of novel organic ligands for separation are discussed.
Co-reporter:Li-Yong Yuan, Ya-Lan Liu, Wei-Qun Shi, Zi-jie Li, Jian-Hui Lan, Yi-Xiao Feng, Yu-Liang Zhao, Ya-Li Yuan and Zhi-Fang Chai
Journal of Materials Chemistry A 2012 vol. 22(Issue 33) pp:17019-17026
Publication Date(Web):27 Jun 2012
DOI:10.1039/C2JM31766D
Due to the rapid development of the nuclear power industry, and consequently, the nuclear accident in Fukushima, much attention has been paid to novel materials for the efficient and rapid separation, removal and recovery of nuclear fuel associated radionuclides from aqueous solutions. Herein, a novel mesoporous material, dihydroimidazole functionalized SBA-15 (DIMS), was synthesized via a post-grafting method and used as an efficient sorbent for the extraction of U(VI) from aqueous solution. The synthesized material was found to possess highly ordered mesoporous structures with a large surface area and a uniform pore diameter. The sorption tests under various conditions demonstrated that the sorption of U(VI) by DIMS was fast, with an equilibrium time of less than 10 min. Additionally, the maximum sorption capacity reached 268 mg g−1 at pH 5.0 ± 0.1. Changes in the solid-to-liquid ratio (msorbent/Vsolution) did not have any remarkable effect on the U(VI) sorption. Besides, the sorbed U(VI) can be easily desorbed by 0.01 mol L−1 or more concentrated HNO3 solution, resulting in a U(VI) solution with a concentration factor of 300 at a solid–liquid ratio as low as 0.013 g L−1. The reclaimed sorbent can be reused with no obvious decrease in the sorption capacity. The selectivity of the DIMS sorbent for U(VI) ions was found to be fairly desirable by the sorption tests with the solutions containing a range of competing metal ions.
Co-reporter:XiaoLiang Wang;LiYong Yuan;YanFei Wang;ZiJie Li;JianHui Lan
Science China Chemistry 2012 Volume 55( Issue 9) pp:1705-1711
Publication Date(Web):2012/09/01
DOI:10.1007/s11426-012-4625-7
Mesoporous silicas have a very attractive ability of sorption and enrichment of metal ions due to their huge surface area and facile functionalization by organic ligands. In this work, phosphonate-amino bifunctionalized mesoporous silica SBA-15 (PA-SBA-15) as U(VI) sorbent was fabricated through post-grafting method. The obtained mesoporous silica was characterized by SEM, XRD, NMR and nitrogen sorption/desorption experiments, which revealed the existence of ordered mesoporous structure with uniform pore diameter and large surface area. The adsorptivity of PA-SBA-15 for U(VI) from aqueous solution was investigated using batch sorption technique under different experimental conditions. The preliminary results show that the U(VI) sorption by PA-SBA-15 is very quick with equilibrium time of less than 1 h, and the U(VI) uptake is as large as 373 mg/g at pH 5.5 under 95 °C. The sorption isotherm has been successfully modeled by the Langmuir isotherm, suggesting a monolayer homogeneous sorption of U(VI) in PA-SBA-15. The sorption is pH-dependent due to the pH-dependent charge of sorbent in the aqueous solution. The thermodynamics research shows that the sorption is a feasible and endothermic process. Based on these results, PA-SBA-15 could be a promising solid phase sorbent for highly-efficient removal of U(VI) ions from waste water and enrichment of U(VI) from a solution at a very low level.
Co-reporter:Jian-Hui Lan, Wei-Qun Shi, Li-Yong Yuan, Yi-Xiao Feng, Yu-Liang Zhao, and Zhi-Fang Chai
The Journal of Physical Chemistry A 2012 Volume 116(Issue 1) pp:504-511
Publication Date(Web):November 27, 2011
DOI:10.1021/jp206793f
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 NO3–, Cl–, and ClO4–. According to our calculations, Am(III) and Eu(III) can chelate eight or nine water molecules at most, whereas more stable species like M(NO3)3(H2O)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(H2O)4]3+ and ML(NO3)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(NO3)3(H2O)4 → ML(NO3)3 and [M(NO3)(H2O)7]2+ → [ML2(NO3)]2+ are probably the dominant ones in the Am(III)/Eu(III) separation process.
Co-reporter:Jian-Hui Lan, Wei-Qun Shi, Li-Yong Yuan, Yu-Liang Zhao, Jun Li, and Zhi-Fang Chai
Inorganic Chemistry 2011 Volume 50(Issue 19) pp:9230-9237
Publication Date(Web):August 25, 2011
DOI:10.1021/ic200078j
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(NO3)3(H2O)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(NO3)3(H2O)4 more favorable in energy, which may thus increase the possibility of formation of Am(BTBPs)(NO3)3. Our work may shed light on the design of novel extractants for Am(III)/Eu(III) separation.
Co-reporter:Li-Yong Yuan, Ya-Lan Liu, Wei-Qun Shi, Yu-Long Lv, Jian-Hui Lan, Yu-Liang Zhao and Zhi-Fang Chai
Dalton Transactions 2011 vol. 40(Issue 28) pp:7446-7453
Publication Date(Web):17 Jun 2011
DOI:10.1039/C1DT10085H
The renaissance of nuclear energy promotes increasing basic research on the separation and enrichment of nuclear fuel associated radionuclides. Herein, we report the first study for developing mesoporous silica functionalized with phosphonate (NP10) as a sorbent for U(VI) sorption from aqueous solution. The mesoporous silica was synthesized by co-condensation of diethylphosphatoethyltriethoxysilane (DPTS) and tetraethoxysilane (TEOS), using cationic surfactant cetyltrimethylammonium bromide (CTAB) as the template. The synthesized silica nanoparticles were observed to possess a mesoporous structure with a uniform pore diameter of 2.7 nm, and to have good stability and high efficiency for U(VI) sorption from aqueous solution. A maximum sorption capacity of 303 mg g−1 and fast equilibrium time of 30 min were achieved under near neutral conditions at room temperature. The adsorbed U(VI) can be easily desorbed by using 0.1 mol L−1HNO3, and the reclaimed mesoporous silica can be reused with no decrease of sorption capacity. In addition, the preconcentration of U(VI) from a 100 mL aqueous solution using the functionalized mesoporous silica was also studied. The preconcentration factor was found to be as high as 100, suggesting the vast opportunities of this kind of mesoporous silica for the solid-phase extraction and enrichment of U(VI).
Co-reporter:Zi-Jie Li, Lin Wang, Li-Yong Yuan, Cheng-Liang Xiao, Lei Mei, Li-Rong Zheng, Jing Zhang, Ju-Hua Yang, Yu-Liang Zhao, Zhen-Tai Zhu, Zhi-Fang Chai, Wei-Qun Shi
Journal of Hazardous Materials (15 June 2015) Volume 290() pp:26-33
Publication Date(Web):15 June 2015
DOI:10.1016/j.jhazmat.2015.02.028
•Uranium removal by ZVI-nps: independent of pH, the presence of CO32−, humic acid, or mimic groundwater constituents.•Rapid removal kinetics and sorption capacity of ZVI-nps is 8173 mg U/g.•Two reaction mechanisms: sufficient Fe0 → reductive precipitation as U3O7; insufficient Fe0 → hydrolysis precipitation of U(VI).•Fe/graphene composites: improved kinetics and higher U(VI) reduction ratio.Zero-valent iron nanoparticle (ZVI-np) and its graphene composites were prepared and applied in the removal of uranium under anoxic conditions. It was found that solutions containing 24 ppm U(VI) could be completely cleaned up by ZVI-nps, regardless of the presence of NaHCO3, humic acid, mimic groundwater constituents or the change of solution pH from 5 to 9, manifesting the promising potential of this reactive material in permeable reactive barrier (PRB) to remediate uranium-contaminated groundwater. In the measurement of maximum sorption capacity, removal efficiency of uranium kept at 100% until C0(U) = 643 ppm, and the saturation sorption of 8173 mg U/g ZVI-nps was achieved at C0(U) = 714 ppm. In addition, reaction mechanisms were clarified based on the results of SEM, XRD, XANES, and chemical leaching in (NH4)2CO3 solution. Partially reductive precipitation of U(VI) as U3O7 was prevalent when sufficient iron was available; nevertheless, hydrolysis precipitation of U(VI) on surface would be predominant as iron got insufficient, characterized by releases of Fe2+ ions. The dissolution of Fe0 cores was assigned to be the driving force of continuous formation of U(VI) (hydr)oxide. The incorporation of graphene supporting matrix was found to facilitate faster removal rate and higher U(VI) reduction ratio, thus benefitting the long-term immobilization of uranium in geochemical environment.Download full-size image
Co-reporter:Wencai Cheng, Congcong Ding, Qunyan Wu, Xiangxue Wang, Yubing Sun, Weiqun Shi, Tasawar Hayat, Ahmed Alsaedi, Zhifang Chai and Xiangke Wang
Environmental Science: Nano 2017 - vol. 4(Issue 5) pp:NaN1131-1131
Publication Date(Web):2017/03/20
DOI:10.1039/C7EN00114B
The competitive interaction of U(VI) and Sr(II) on graphene oxides (GOs) was studied by batch techniques, EXAFS analysis and DFT calculations. The batch results indicated that decreased sorption of Sr(II) on GOs was observed at C[U(VI)] < 0.2 mmol L−1 and enhanced sorption of Sr(II) was found at C[U(VI)] > 0.2 mmol L−1, whereas the presence of Sr(II) did not affect U(VI) sorption on GOs. The increased sorption of Sr(II) at C[U(VI)] > 0.2 mmol L−1 resulted from the new available sites provided by the precipitated U(VI) or adsorbed hydrolyzed U(VI) species according to EXAFS analysis. The occurrence of a U–C shell in the absence/presence of Sr(II) indicated that U(VI) tended to form inner-sphere surface complexes with GOs. For the Sr(II) interaction, a Sr–C shell was observed at a low U(VI) concentration, but not formed at a high U(VI) concentration, indicating the shift of inner-sphere to outer-sphere surface complexes with increasing U(VI) concentration. According to DFT calculation, the binding energy of GO–U(VI) (e.g., −40.3 kcal mol−1 for inner-sphere coordination) was significantly lower than that of GO–Sr(II) (−16.4 kcal mol−1), demonstrating that U(VI) was preferentially bound to GOs relative to Sr(II). These findings can provide a reliable prediction of the transport and fates of U(VI) and Sr(II) at the water–GO interface and open doorways for the application of GOs.
Co-reporter:Zhen-ni Xie, Lei Mei, Qun-yan Wu, Kong-qiu Hu, Liang-shu Xia, Zhi-fang Chai and Wei-qun Shi
Dalton Transactions 2017 - vol. 46(Issue 23) pp:NaN7396-7396
Publication Date(Web):2017/05/01
DOI:10.1039/C7DT01034F
The first reversible solid-state single-crystal-to-single-crystal isomerisation mediated by the change of uranyl-ligand coordination modes, that is from seven-coordinated uranium(VI) of α-UP to six-coordinated uranium(VI) of the supramolecular isomer, β-UP, has been achieved in the uranyl polyrotaxane system by a temperature-induced strategy.
Co-reporter:Shu-wen An, Lei Mei, Cong-zhi Wang, Chuan-qin Xia, Zhi-fang Chai and Wei-qun Shi
Chemical Communications 2015 - vol. 51(Issue 43) pp:NaN8981-8981
Publication Date(Web):2015/04/10
DOI:10.1039/C5CC02646F
The first actinide triple helices, including two supramolecular conformational isomers of uranium(VI), have been synthesized with the aid of a flexible V-shaped ligand and a rigid aromatic base. The isomers exhibit an intriguing pH-dependent structural evolution and a kinetically-controlled transformation via a novel conformational rearrangement of the organic base.
Co-reporter:Lei Mei, Qun-yan Wu, Cai-ming Liu, Yu-liang Zhao, Zhi-fang Chai and Wei-qun Shi
Chemical Communications 2014 - vol. 50(Issue 27) pp:NaN3615-3615
Publication Date(Web):2014/02/11
DOI:10.1039/C4CC00690A
In situ assembly of a cucurbituril-based pseudorotaxane and a uranyl nitrate precursor under hydrothermal conditions affords the first actinide polyrotaxane with a unique ‘dragon-like’ twist, which is induced by the specific coordination pattern of uranium and stabilized by hydrogen bonding between the η1-mode carboxylate group and adjacent methylene moieties of CB[6].
Co-reporter:Zhi-Qiang Bai, Li-Yong Yuan, Lin Zhu, Zhi-Rong Liu, Sheng-Qi Chu, Li-Rong Zheng, Jing Zhang, Zhi-Fang Chai and Wei-Qun Shi
Journal of Materials Chemistry A 2015 - vol. 3(Issue 2) pp:NaN534-534
Publication Date(Web):2014/11/11
DOI:10.1039/C4TA04878D
Metal–organic frameworks (MOFs) have recently been receiving increasing attention in various scientific fields, including nuclear industry, due to their unique properties. In this work, the acid-resistant chromium-based MOF, MIL-101, and its amino derivatives were prepared to explore their potential usage in separation, removal and/or recovery of radionuclides from aqueous solutions. The synthesized MIL-101-NH2, MIL-101-ED (ED = Ethanediamine), and MIL-101-DETA (DETA = Diethylenetriamine) were characterized by X-ray diffraction spectrometry (XRD), infrared spectrometry (IR), N2 adsorption–desorption measurements, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), which confirm the successful modification of amino groups and the preservation of porous structures. The sorption performances of these materials toward U(VI) from an aqueous solution were investigated in detail. It was found that all the amine-grafted MOFs were highly efficient in capturing U(VI) compared to raw MIL-101. The sorption capacity of these MOFs for U(VI) sorption follows the order of MIL-101-DETA > MIL-101-ED > MIL-101-NH2 > MIL-101, in which MIL-101-DETA possesses the highest sorption capacity of 350 mg g−1 at pH ∼5.5. Moreover, the sorbed U(VI) can be easily desorbed by lowering the pH (pH ≤ 3.0), and the prepared materials also display a desirable selectivity toward U(VI) in a solution containing a range of competing ions. Based on the FTIR and EXAFS characterizations, the sorption mode of U(VI) onto MOFs is fully discussed. This work promises to provide a facile approach for developing acid-resistant MOFs toward a highly efficient and selective extraction of radionuclides from aqueous solutions.
Co-reporter:Li-Yong Yuan, Ya-Lan Liu, Wei-Qun Shi, Zi-jie Li, Jian-Hui Lan, Yi-Xiao Feng, Yu-Liang Zhao, Ya-Li Yuan and Zhi-Fang Chai
Journal of Materials Chemistry A 2012 - vol. 22(Issue 33) pp:
Publication Date(Web):
DOI:10.1039/C2JM31766D
Co-reporter:Tao Bo, Jian-Hui Lan, Yu-Juan Zhang, Yao-Lin Zhao, Chao-Hui He, Zhi-Fang Chai and Wei-Qun Shi
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 19) pp:NaN13266-13266
Publication Date(Web):2016/04/11
DOI:10.1039/C6CP01175F
The interfacial interaction of uranium mononitride (UN) with water from the environment unavoidably leads to corrosion of nuclear fuels, which affects a lot of processes in the nuclear fuel cycle. In this work, the microscopic adsorption behaviors of water on the UN(001) surface as well as water dissociation and accompanying H2 formation mechanisms have been investigated on the basis of DFT+U calculations and ab initio atomistic thermodynamics. For adsorption of one H2O monomer, the predicted adsorption energies are −0.88, −2.07, and −2.07 eV for the most stable molecular, partially dissociative, and completely dissociative adsorption, respectively. According to our calculations, a water molecule dissociates into OH and H species via three pathways with small energy barriers of 0.78, 0.72, and 0.85 eV, respectively. With the aid of the neighboring H atom, H2 formation through the reaction of H* + OH* can easily occur via two pathways with energy barriers of 0.61 and 0.36 eV, respectively. The molecular adsorption of water shows a slight coverage dependence on the surface while this dependence becomes obvious for partially dissociative adsorption as the water coverage increases from 1/4 to 1 ML. In addition, based on the “ab initio atomistic thermodynamic” simulations, increasing H2O partial pressure will enhance the stability of the adsorbed system and water coverage, while increasing temperature will decrease the H2O coverage. We found that the UN(001) surface reacts easily with H2O at room temperature, leading to dissolution and corrosion of the UN fuel materials.
Co-reporter:Li-Yong Yuan, Ya-Lan Liu, Wei-Qun Shi, Yu-Long Lv, Jian-Hui Lan, Yu-Liang Zhao and Zhi-Fang Chai
Dalton Transactions 2011 - vol. 40(Issue 28) pp:NaN7453-7453
Publication Date(Web):2011/06/17
DOI:10.1039/C1DT10085H
The renaissance of nuclear energy promotes increasing basic research on the separation and enrichment of nuclear fuel associated radionuclides. Herein, we report the first study for developing mesoporous silica functionalized with phosphonate (NP10) as a sorbent for U(VI) sorption from aqueous solution. The mesoporous silica was synthesized by co-condensation of diethylphosphatoethyltriethoxysilane (DPTS) and tetraethoxysilane (TEOS), using cationic surfactant cetyltrimethylammonium bromide (CTAB) as the template. The synthesized silica nanoparticles were observed to possess a mesoporous structure with a uniform pore diameter of 2.7 nm, and to have good stability and high efficiency for U(VI) sorption from aqueous solution. A maximum sorption capacity of 303 mg g−1 and fast equilibrium time of 30 min were achieved under near neutral conditions at room temperature. The adsorbed U(VI) can be easily desorbed by using 0.1 mol L−1HNO3, and the reclaimed mesoporous silica can be reused with no decrease of sorption capacity. In addition, the preconcentration of U(VI) from a 100 mL aqueous solution using the functionalized mesoporous silica was also studied. The preconcentration factor was found to be as high as 100, suggesting the vast opportunities of this kind of mesoporous silica for the solid-phase extraction and enrichment of U(VI).
Co-reporter:Cheng-Liang Xiao, Qun-Yan Wu, Lei Mei, Li-Yong Yuan, Cong-Zhi Wang, Yu-Liang Zhao, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2014 - vol. 43(Issue 33) pp:NaN12473-12473
Publication Date(Web):2014/06/26
DOI:10.1039/C4DT01489H
A preorganized tetradentate phenanthroline-derived amide ligand, N,N′-diethyl-N,N′-ditolyl-2,9-dicarboxamide-1,10-phenanthroline (Et-Tol-DAPhen), was found to show high selectivity towards small copper ions, which might be due to the change of the coordination mechanism from tetradentate to terdentate mode.
Co-reporter:Cong-Zhi Wang, Jian-Hui Lan, Qun-Yan Wu, Yu-Liang Zhao, Xiang-Ke Wang, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2014 - vol. 43(Issue 23) pp:NaN8720-8720
Publication Date(Web):2014/04/09
DOI:10.1039/C4DT00032C
At present, designing novel ligands for efficient actinide extraction in spent nuclear fuel reprocessing is extremely challenging due to the complicated chemical behaviors of actinides, the similar chemical properties of minor actinides (MA) and lanthanides, and the vulnerability of organic ligands in acidic radioactive solutions. In this work, a quantum chemical study on Am(III), Cm(III) and Eu(III) complexes with N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and N,N′-dimethyl-N,N′-diheptyl-3-oxapentanediamide (DMDHOPDA) has been carried out to explore the extraction behaviors of trivalent actinides (An) and lanthanides (Ln) with diglycolamides from acidic media. It has been found that in the 1:1 (ligand:metal) and 2:1 stoichiometric complexes, the carbonyl oxygen atoms have stronger coordination ability than the ether oxygen atoms, and the interactions between metal cations and organic ligands are substantially ionic. The neutral ML(NO3)3 (M = Am, Cm, Eu) complexes seem to be the most favorable species in the extraction process, and the predicted relative selectivities are in agreement with experimental results, i.e., the diglycolamide ligands have slightly higher selectivity for Am(III) over Eu(III). Such a thermodynamical priority is probably caused by the higher stabilities of Eu(III) hydration species and Eu(III)–L complexes in aqueous solution compared to their analogues. In addition, our thermodynamic analysis from water to organic medium confirms that DMDHOPDA has higher extraction ability for the trivalent actinides and lanthanides than TODGA, which may be due to the steric hindrance of the bulky alkyl groups of TODGA ligands. This work might provide an insight into understanding the origin of the actinide selectivity and a theoretical basis for designing highly efficient extractants for actinide separation.
Co-reporter:Cong-Zhi Wang, John K. Gibson, Jian-Hui Lan, Qun-Yan Wu, Yu-Liang Zhao, Jun Li, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2015 - vol. 44(Issue 39) pp:NaN17053-17053
Publication Date(Web):2015/08/27
DOI:10.1039/C5DT02811F
Synthesis of complexes with direct actinide–actinide (An–An) bonding is an experimental ‘holy grail’ in actinide chemistry. In this work, a series of actinide dimetallocenes An2Cp*2 (Cp* = C5(CH3)5, An = Th–Pu) with An–An multiple bonds have been systematically investigated using quantum chemical calculations. The coaxial Cp*–An–An–Cp* structures are found to be the most stable species for all the dimetallocenes. A Th–Th triple bond is predicted in the Th2Cp*2 complex, and the calculated An–An bond orders decrease across the actinide series from Pa to Pu. The covalent character of the An–An bonds is analyzed by using natural bond orbitals (NBO), molecular orbitals (MO), the quantum theory of atoms in molecules (QTAIM), and electron density difference (EDD). While Th 6d orbitals dominate the Th–Th bonds in Th2Cp*2, the An 6d-orbital characters decrease and 5f-orbital characters increase for complexes from Pa2Cp*2 to Pu2Cp*2. All these actinide dimetallocenes are stable in the gas phase relative to the AnCp* reference at room temperature. Based on the reactions of AnCp*2 and An, Th2Cp*2, Pa2Cp*2 and possibly also U2Cp*2 should be accessible as isolated molecules under suitable synthetic conditions. Our results shed light on the molecular design of ligands for stabilizing actinide–actinide multiple bonds.
Co-reporter:Han Wu, Qun-Yan Wu, Cong-Zhi Wang, Jian-Hui Lan, Zhi-Rong Liu, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2015 - vol. 44(Issue 38) pp:NaN16745-16745
Publication Date(Web):2015/08/19
DOI:10.1039/C5DT02528A
Due to the similar chemical properties of actinides An(III) and lanthanides Ln(III), their separation in spent nuclear fuel reprocessing is extremely challenging. A 1,10-phenanthroline dipicolinamide-based ligand (PhenBHPPA) has been identified to possess a selectivity for Am(III) over Eu(III) and could potentially be used for group actinide extraction. In this study, quasi-relativistic density functional theoretical calculations have been used to disclose the interaction mechanisms of Am(III) and Eu(III) complexes with PhenBHPPA. The electronic structures, bonding nature, QTAIM (Quantum Theory of Atoms in Molecules) analyses and thermodynamic behaviors of the Am(III) and Eu(III) complexes with PhenBHPPA have been explored in detail. According to the Wiberg bond indices (WBIs) and QTAIM analyses, interactions between the ligand and metal cations (Am(III) and Eu(III)) exhibit a weakly covalent character. Thermodynamic analyses show that the charged complexes [ML(NO3)2]+ appear to be the most stable species in the complexation processes. Moreover, it is more energetically favorable for PhenBHPPA to bind to Am(III) compared to Eu(III). Our study could render new insights into understanding the selectivity of the ligand towards minor actinides and the separation of An(III) from Ln(III) via liquid–liquid extraction.
Co-reporter:Cheng-Liang Xiao, Cong-Zhi Wang, Lei Mei, Xin-Rui Zhang, Nathalie Wall, Yu-Liang Zhao, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2015 - vol. 44(Issue 32) pp:NaN14387-14387
Publication Date(Web):2015/07/08
DOI:10.1039/C5DT01766A
The tetradentate N,N′-diethyl-N,N′-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) ligand with hard–soft donor atoms has been demonstrated to be promising for the group separation of actinides from highly acidic nuclear wastes. To identify the formed complexes of this ligand with actinides and lanthanides, electrospray ionization mass spectrometry (ESI-MS) combined with density functional theory (DFT) calculations was used to probe the possible complexation processes. The 1:2 Eu–L species ([EuL2(NO3)]2+) can be observed in ESI-MS at low metal-to-ligand ([M]/[L]) ratios, whereas the 1:1 Eu–L species ([EuL(NO3)2]+) can be observed when the [M]/[L] ratio is higher than 1.0. However, ([UO2L(NO3)]+) is the only detected species for the uranyl complexes. The [ThL2(NO3)2]2+ species can be observed at low [M]/[L] ratios; the 1:2 species ([ThL2(NO3)]3+) and a new 1:1 species ([ThL(NO3)3]+) can be detected at high [M]/[L] ratios. Collision-induced dissociation (CID) results showed that Et-Tol-DAPhen ligands can coordinate strongly with metal ions, and the coordination moieties remain intact under CID conditions. Natural bond orbital (NBO), molecular electrostatic potential (MEP), electron localization function (ELF), atoms in molecules (AIM) and molecular orbital (MO) analyses indicated that the metal–ligand bonds of the actinide complexes exhibited more covalent character than those of the lanthanide complexes. In addition, according to thermodynamic analysis, the stable cationic M–L complexes in acetonitrile are found to be in good agreement with the ESI-MS results.
Co-reporter:Juan Luo, Cong-Zhi Wang, Jian-Hui Lan, Qun-Yan Wu, Yu-Liang Zhao, Zhi-Fang Chai, Chang-Ming Nie and Wei-Qun Shi
Dalton Transactions 2015 - vol. 44(Issue 7) pp:NaN3236-3236
Publication Date(Web):2014/12/24
DOI:10.1039/C4DT03321C
Actinide separation in spent nuclear fuel reprocessing is essential for the closed nuclear fuel cycle. Organophosphorus reagents have been found to exhibit strong affinities for actinides in experiments. In this work, the extraction complexes of AnO2n+ (An = U, Np; n = 1, 2) with the traditional organophosphorus ligand HDEHP (di-(2-ethylhexyl)phosphoric acid) have been investigated using density functional theory together with scalar-relativistic effective core potentials (ECPs) for actinide elements. According to our calculations, the HDEHP dimer prefers to act as a bidentate ligand in most of the studied complexes. HDEHP ligands show a higher extraction ability for An(VI) over An(V), and the formation of Np(VI) complexes is slightly more favorable than those of U(VI) analogues, which is mainly attributed to the stronger donor–acceptor interaction in Np(VI) complexes. The intramolecular hydrogen bonds play a significant role in the stability of the 1:1 type complexes AnO2(HL)2(NO3)2 (L = DEHP−). Moreover, AnO2(HL)2(NO3)2 are the most stable species in nitrate-rich acid solutions, while at low nitric acid concentrations, the complexing reaction of AnO2(H2O)52+ + 2(HL)2 → AnO2(HL2)2 + 2H+ + 5H2O is probably the dominant reaction in the extraction process. Our results can help to understand the speciation of actinyl complexes in real solvent extraction of actinides with HDEHP at the molecular level.
Co-reporter:Lei Mei, Zhen-ni Xie, Kong-qiu Hu, Lin Wang, Li-yong Yuan, Zi-jie Li, Zhi-fang Chai and Wei-qun Shi
Dalton Transactions 2016 - vol. 45(Issue 34) pp:NaN13307-13307
Publication Date(Web):2016/07/20
DOI:10.1039/C6DT02704K
The first 3D actinide polyrotaxane framework (named IHEP-URCP-2) has been obtained based on windmill-like six-connected high-nuclear oligomeric uranyl nodes under hydrothermal conditions. Notably, the in situ formed pseudorotaxane ligand simultaneously plays dual roles of both a bulky pseudorotaxane linker and a supramolecular guest.
Co-reporter:Han Wu, Qun-Yan Wu, Cong-Zhi Wang, Jian-Hui Lan, Zhi-Rong Liu, Zhi-Fang Chai and Wei-Qun Shi
Dalton Transactions 2016 - vol. 45(Issue 19) pp:NaN8117-8117
Publication Date(Web):2016/03/30
DOI:10.1039/C6DT00296J
Although many heterocyclic N-donor ligands have shown excellent competence for separating actinides from lanthanides, an explanation for why some ligands work whereas others fail is very fundamental but greatly needs to be addressed for designing novel and efficient extractants. In this work, we systematically investigated four phenanthroline-derived ligands, DHDIPhen, BQPhen, Ph2-BTPhen and CyMe4-BTPhen, and their coordination geometrical properties and formation reactions with Am(III) and Eu(III) ions by quasi-relativistic density functional theory. The calculated hardness of ligands, which may help to determine their selectivity toward actinides and lanthanides, yielded an order, from the softest to the hardest, as follows: Ph2-BTPhen < CyMe4-BTPhen < BQPhen < DHDIPhen. It shows that the intramolecular hydrogen bonds and size of a ligand cavity are two dominant factors for metal-ion complexation. Natural population analysis (NPA) reveals that the 5d/6d orbitals of Eu/Am accept significantly more electrons than other orbitals, but partial density of states and molecular orbital analysis prove that the d orbitals with more accepted electrons have little contribution to the metal–ligand bonds. The thermodynamic results suggest that ligand protonation does have a great influence on the complexation of ligands with metal ions but does not change the selectivity of ligands toward metal ions. This work can help in-depth understanding the differences of selectivity of various structurally similar ligands and provide more theoretical insights for designing more innovative ligands for Ln/An separation.
Co-reporter:Q.-Y. Wu, J.-H. Lan, C.-Z. Wang, Z.-P. Cheng, Z.-F. Chai, J. K. Gibson and W.-Q. Shi
Dalton Transactions 2016 - vol. 45(Issue 7) pp:NaN3110-3110
Publication Date(Web):2016/01/05
DOI:10.1039/C5DT04540A
Recently, the +2 formal oxidation state in soluble molecular complexes for lanthanides (La–Nd, Sm–Lu) and actinides (Th and U) has been discovered [W. J. Evans, et al., J. Am. Chem. Soc., 2011, 133, 15914; J. Am. Chem. Soc., 2012, 134, 8420; J. Am. Chem. Soc., 2013, 135, 13310; Chem. Sci., 2015, 6, 517]. To explore the nature of the bonding and stabilities of the low-valent actinide complexes, a series of divalent actinide species, [AnCp′3]− (AnTh–Am, Cp′ = [η5-C5H4(SiMe3)]−) have been investigated in THF solution using scalar relativistic density functional theory. The electronic structures and electron affinity properties were systematically studied to identify the interactions between the +2 actinide ions and Cp′ ligands. The ground state electron configurations for the [AnCp′3]− species are [ThCp′3]− 6d2, [PaCp′3]− 5f26d1, [UCp′3]− 5f36d1, [NpCp′3]− 5f5, [PuCp′3]− 5f6, and [AmCp′3]− 5f7, respectively, according to the MO analysis. The total bonding energy decreases from the Th- to the Am-complex and the electrostatic interactions mainly dominate the bonding between the actinide atom and ligands. The electron affinity analysis suggests that the reduction reaction of AnCp′3 → [AnCp′3]− should become increasingly facile across the actinide series from Th to Am, in accord with the known An(III/II) reduction potentials. This work expands the knowledge on the low oxidation state chemistry of actinides, and further motivates and guides the synthesis of related low oxidation state compounds of 5f elements.
Co-reporter:Weiting Yang, Zhi-Qiang Bai, Wei-Qun Shi, Li-Yong Yuan, Tao Tian, Zhi-Fang Chai, Hao Wang and Zhong-Ming Sun
Chemical Communications 2013 - vol. 49(Issue 88) pp:NaN10417-10417
Publication Date(Web):2013/09/10
DOI:10.1039/C3CC44983A
MOF-76 exhibits not only high sensitivity for the detection of U(VI), but also high adsorption capacity of 298 mg g−1 at a low pH value of ∼3.0. Furthermore, the high selectivity for uranium adsorption over a series of competing metal ions is also illustrated.
Co-reporter:Lei Mei, Lin Wang, Li-yong Yuan, Shu-wen An, Yu-liang Zhao, Zhi-fang Chai, Peter C. Burns and Wei-qun Shi
Chemical Communications 2015 - vol. 51(Issue 60) pp:NaN11993-11993
Publication Date(Web):2015/06/22
DOI:10.1039/C5CC04409J
The assembly of two-dimensional (2D) large channel uranyl–organic polyrotaxane networks as well as structural regulation of uranyl-bearing units using jointed cucurbit[6]uril-based pseudorotaxanes with integral rigidity based on supramolecular inclusion is presented for the first time. This construction strategy concerning controlling molecular integral rigidity based on supramolecular inclusion may afford an entirely new methodology for coordination chemistry.
Co-reporter:Shu-wen An, Lei Mei, Kong-qiu Hu, Chuan-qin Xia, Zhi-fang Chai and Wei-qun Shi
Chemical Communications 2016 - vol. 52(Issue 8) pp:NaN1644-1644
Publication Date(Web):2015/11/23
DOI:10.1039/C5CC09314G
Two novel tetra-nuclear uranyl-mediated two-fold interpenetrating networks, [U4O10(dbsf)3]2[H2bpp]2 and [U4O10(dbsf)3][H2bpp], have been hydrothermally synthesized from a semi-rigid carboxylic acid, H2dbsf, with the organic base, bpp, as the charge balancing agent and stacking template (H2dbsf = 4,4′-dicarboxybiphenyl sulfone, bpp = 1,3-di(4-pyridyl)propane).
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![N-{2-[bis(carboxymethyl)amino]ethyl}glycine](http://img.cochemist.com/ccimg/700/688-57-3.png)
![N-{2-[bis(carboxymethyl)amino]ethyl}glycine](http://img.cochemist.com/ccimg/700/688-57-3_b.png)
![Uranium,dioxo[sulfato(2-)-kO]-](http://img.cochemist.com/ccimg/1400/1314-64-3.png)
![Uranium,dioxo[sulfato(2-)-kO]-](http://img.cochemist.com/ccimg/1400/1314-64-3_b.png)
