Qingnuan Li

The extraction of uranium using graphene aerogel loading organic solution

A new approach for uranium extraction employing graphene aerogel (GA) as a skeleton loading organic solution (GA-LOS) is proposed and investigated. Firstly, the GA with super-hydrophobicity and high organic solution absorption capacity was fabricated by one-step reduction and self-assembly of graphene oxide with ethylenediamine. By adsorbing Tri-n-butyl phosphate (TBP)/n-dodecane solution to prepare GA-LOS, the extraction of U(VI) from nitric acid medium using GA-LOS was investigated and compared with conventional solvent extraction. It is found that the GA-LOS method can provide several advantages over conventional solvent extraction and adsorption due to the elimination of aqueous-organic mixing-separation procedures and easy solid-liquid separation. Furthermore, it also possesses higher extraction capacity (the saturated extraction capacity of GA loading TBP for U(VI) was 316.3mgg-1 ) and lower consumption of organic diluents, leading to less organic waste. Moreover, the stability of GA-LOS in aqueous solution and cycling test were also studied, and it shows a remarkable regeneration capability, making it an ideal candidate for metal extraction from aqueous solution.

Formation and Characterization of Homoleptic Thorium Isocyanide Complexes

Homoleptic thorium isocyanide complexes have been prepared via the reactions of laser-ablated thorium atoms and (CN)2 in a cryogenic matrix, and the structures of the products were characterized by infrared spectroscopy and theoretical calculations. Thorium atoms reacted with (CN)2 under UV irradiation to form the oxidative addition product Th(NC)2, which was calculated to have closed-shell singlet ground state with a bent geometry. Further reaction of Th(NC)2 and (CN)2 resulted in the formation of Th(NC)4, a molecule with a tetrahedral geometry. Minor products such as ThNC and Th(NC)3 were produced upon association reactions of CN with Th and Th(NC)2. Homoleptic thorium cyanide isomers Th(CN)x (x = 1-4) are predicted to be less stable than the corresponding isocyanides. The C-N stretches of thorium cyanides were calculated to be between 2170 and 2230 cm-1 at the B3LYP level, more than 120 cm-1 higher than the N-C stretches of isocyanides and with much weaker intensities. No experimental absorptions appeared where Th(CN)x should be observed.

Coordination Structure and Fragmentation Chemistry of the Tripositive Lanthanide-Thio-Diglycolamide Complexes

Tripositive Ln(TMTDA)33+ complexes (Ln = La-Lu except Pm, TMTDA = tetramethyl 3-thio-diglycolamide) were observed in the gas phase by electrospray ionization of LnCl3 and TMTDA mixtures. Collision-induced dissociation (CID) was employed to investigate their fragmentation chemistry, which revealed the influence of metal center as well as ligand on the ligated complexes. Ln(TMTDA)2(TMTDA-45)3+ resulting from Ccarbonyl-N bond cleavage of TMTDA and hydrogen transfer was the major CID product for all Ln(TMTDA)33+ except Eu(TMTDA)33+, which predominantly formed charge-reducing product EuII(TMTDA)22+ via electron transfer from TMTDA to Eu3+. Density functional theory calculations on the structure of La(TMTDA)33+ and Lu(TMTDA)33+ revealed that Ln3+ was coordinated by six Ocarbonyl atoms from three neutral TMTDA ligands, and both complexes possessed C3h symmetry. The Sether atom deviating from the ligand plane was not coordinated to the metal center. On the basis of the CID results of Ln(TMTDA)33+, Ln(TMGA)33+, and Ln(TMOGA)33+, the fragmentation chemistry associated with the ligand depends on the coordination mode, while the redox chemistry of these tripositive ions is related to the nature of both metal centers and diamide ligands.

Infrared Spectroscopic and Theoretical Studies of Group 3 Metal Isocyanide Molecules

A series of group 3 metal isocyanide complexes were prepared via the reactions of laser ablated scandium, yttrium, and lanthanum atoms with (CN)2 in an argon matrix. The product structures were identified on the basis of their characteristic infrared absorptions from isotopically labeled (CN)2 samples as well as the calculated frequencies and isotopic frequency ratios. Group 3 metal atoms reacted with (CN)2 to form M(NC)2 (M = Sc, Y, La) when the samples were subjected to λ > 220 nm irradiation. Other products such as M(NC)3 and MNC were produced together with M(NC)2 through either the reactions of M(NC)2 and (CN)2 or the loss of one CN ligand from M(NC)2. CCSD(T)//B3LYP calculations reveal that ScNC possesses a 3Δ ground state, while 1Σ+ is most stable for YNC and LaNC. All of the M(NC)2 and M(NC)3 complexes were predicted to have doublet and singlet ground states, respectively. Group 3 metal cyanides are less stable than the isocyanides by at least 4 kcal/mol at the CCSD(T) level, and their C-N stretches are much weaker than the N-C stretches of the isocyanides. No absorption can be assigned to the M(CN) x complex, which would appear between 2100 and 2250 cm-1.

Investigating the influence of F− on U4+ in molten LiCl–KCl–UF4 system and electro-deposition of U

Electrochemical behaviors of U4+ in LiCl–KCl–UF4 eutectic and deposition of U metal were investigated. It was found that the presence of F− has influence on the diffusion of U3+ and U4+ as comparing to data obtained in pure chloride molten salts. Electrochemical deposition of U was carried out by using pulse current electrolysis. Characterization results indicate that U metal was obtained at the cathode, implying U metal can be directly deposited from LiCl–KCl–UF4 eutectic in this case and the extractive ratio is calculated to be 98%. Our results demonstrate feasible separation of U from LiCl–KCl–UF4 molten salt by electrochemical method.

Application of polyantimonic acid–polyacrylonitrile for removal of strontium(II) from simulated high-level liquid waste

Applicability of polyantimonic acid–polyacrylonitrile (PAA–PAN) in 60–150 mesh for removal of strontium(II) from simulated high-level liquid waste (HLLW) was investigated in this paper. The adsorption behavior of Sr(II) and other typical fission products (FPs) onto PAA–PAN was determined by using batch experiments. The results show that PAA–PAN exhibited high adsorption affinity for Sr(II) in HNO3 medium, and other FPs except for Zr, which could be eluted by H2C2O4–HNO3, were weakly adsorbed on PAA–PAN. Then, a column experiment was performed to remove Sr(II) from simulated HLLW, and it’s found that Sr(II) could be effectively transferred onto the PAA–PAN column from HLLW.

Matrix Infrared Spectra of Manganese and Iron Isocyanide Complexes

Mono and diisocyanide complexes of manganese and iron were prepared via the reactions of laser-ablated manganese and iron atoms with (CN)2 in an argon matrix. Product identifications were performed based on the characteristic infrared absorptions from isotopically labeled (CN)2 experiments as compared with computed values for both cyanides and isocyanides. Manganese atoms reacted with (CN)2 to produce Mn(NC)2 upon λ > 220 nm irradiation, during which MnNC was formed mainly as a result of the photoinduced decomposition of Mn(NC)2. Similar reaction products FeNC and Fe(NC)2 were formed during the reactions of Fe and (CN)2. All the product molecules together with the unobserved cyanide isomers were predicted to have linear geometries at the B3LYP level of theory. The cyanide complexes of manganese and iron were computed to be more stable than the isocyanide isomers with energy differences between 0.4 and 4 kcal/mol at the CCSD(T) level. Although manganese and iron cyanide molecules are slightly more stable according to the theory, no absorption can be assigned to these isomers in the region above the isocyanides possibly due to their low infrared intensities.

Infrared Spectroscopic and Theoretical Studies on the OMF2 and OMF (M = Cr, Mo, W) Molecules in Solid Argon

Group 6 metal oxide fluoride molecules in the form of OMF2 and OMF (M = Cr, Mo, W) were prepared via the reactions of laser-ablated metal atoms and OF2 in excess argon. Product identifications were performed by using infrared spectroscopy, 18OF2 samples, and electronic structure calculations. Reactions of group 6 metal atoms and OF2 resulted in the formation of ternary OCrF2, OMoF2, and OWF2 molecules with C2v symmetry in which the tetravalent metal center is coordinated by one oxygen and two fluorine atoms. Both OCrF2 and OMoF2 are computed to possess triplet ground states, and a closed shell singlet is the ground state for OWF2. Triatomic OCrF, OMoF, and OWF molecules were also observed during sample deposition. All three molecules were computed to have a bent geometry and quartet ground state. A bonding analysis showed that the OMF2 molecules have highly ionic M-F bonds. 3OCrF2 and 3OMoF2 have an M-O double bond composed of a σ bond and a π bond. 1OWF2 has an M-O triple bond consisting of a σ bond, a π bond, and a highly delocalized O lone pair forming the other π bond. The M-O bonds in the OMF compounds have triple-bond character for all three metals.