Organic and Aqueous Redox Speciation of Cu(III) Periodate Oxidized Transuranium Actinides

Efficient degradation and detoxification of antibiotic Fosfomycin by UV irradiation in the presence of persulfate

Fosfomycin (FOS) as a widely used antibiotic has been found in abundance throughout the environment, but little effort has been devoted to its treatment. In this study, we systemically looked into the degradation of FOS by ultraviolet-activated persulfate (UV/PS) in aqueous solutions. Our findings demonstrated that FOS can be degraded efficiently under the UV/PS, e.g., >90 % of FOS was degraded with 19,200 mJ cm-2 of UV irradiance and 20 μM of PS. HO was the dominant radical responsible for FOS degradation. FOS degradation increased as PS dosage increased, and higher degradation efficiency was observed at neutral pH. Natural water constitutes either promoted (e.g., Cu2+, Fe3+, and SO42-) or inhibited (e.g., humic acid, HCO3-, and CO32-) FOS degradation to varying degrees. Hydroxyl substitution, CP bond cleavage, and coupling reactions were the major degradation pathways for FOS degradation. Finally, the toxicity evaluation revealed that FOS was toxic to E. coli and S. aureus, but the toxicity of the intermediate products of FOS to E. coli and S. aureus rapidly decreased over time after UV/PS treatment. Therefore, these findings provided a fundamental understanding of the transformation process of FOS and supplied useful information for the environmental elimination of FOS contamination and its toxicity.

Electrochemical oxidation of trivalent americium using a dipyrazinylpyridine modified ITO electrode

We present here the electrochemical oxidation of Am(iii) to AmVO2+ and AmVIO22+ in pH 1 nitric acid using a mesoporous tin-doped indium oxide electrode modified with a covalently attached dipyrazinylpyridine ligand. The applied potential affects the distribution of Am oxidation products. At potential 1.8 V, only Am(v) is observed, while increasing the potential to as much as 2.0 V, results in oxidation of Am(iii) to Am(v) and subsequent oxidation of Am(v) to Am(vi). At applied potentials >2.0 V, Am(iii) is oxidized to Am(v), while Am(vi) is reduced to Am(v). The latter reduction reaction is likely due to the increased rate of hydrogen peroxide formation from the 2-electron oxidation of water at the electrode at these high potentials. The development of future ligand modified electrodes for actinide oxidations must consider how they facilitate Am oxidations while disfavoring unwanted or competing reactions.

Highly Efficient and Selective Dissolution Separation of Fission Products by an Ionic Liquid [Hbet][Tf2N]: A New Approach to Spent Nuclear Fuel Recycling

Here, we propose the use of carboxyl-functionalized ionic liquid, [Hbet][Tf₂N], to separate the fission products from spent nuclear fuels. This innovative method allows the selective dissolution of neutron poisons, lanthanides oxide, as well as some fission products with high yield, leaving most of the UO₂ matrix and minor actinides behind in the spent nuclear fuel and accomplishing the actinides recovery as a group. Water-saturated [Hbet][Tf₂N] can dissolve lanthanides oxide from simulated spent nuclear fuel with a dissolution ratio of 100% at 40 °C. However, the dissolution of uranium is almost negligible (<1%) under the same conditions. This big difference in dissolution provides a novel separation approach to spent nuclear fuel recycling and may open new perspectives for spent nuclear fuel reprocessing. The recovery of Nd and U from metal-loaded ionic liquids and the recyclability of the ionic liquid [Hbet][Tf₂N] have also been investigated. Furthermore, a U/ x value related to the lattice energy U of metal compound M _xO _y is used to elaborate the solubility. This work represents the first case for efficient fission products removal by selective dissolution, avoiding the complete dissolution of spent nuclear fuel, the producing of the large high-level radioactive waste, and reducing environmental hazards.

Structural Characteristics, Population Analysis, and Binding Energies of [An(NO3)]2+ (with An = Ac to Lr)

Efficient predictive capabilities are essential for the actinide series since regulatory constraints for radioactive work, associated costs needed for specialized facilities, and the short half-lives of many actinides present great challenges in laboratory settings. Improved predictive accuracy is advantageous for numerous applications including the optimization and design of separation agents for nuclear fuel and waste. One limitation of calculations in support of these applications is that the large variations observed from predictions obtained with currently available methods can make comparisons across studies uncertain. Benchmarking currently available computational methodologies is essential to establish reliable practices across the community to guarantee an accurate physical description of the systems studied. To understand the performance of a variety of common theoretical methods, a systematic analysis of differences observed in the prediction of structural characteristics, electron withdrawing effects, and binding energies of [An(NO3)]2+ (with An = Ac to Lr) in gas and aqueous phases is reported. Population analysis obtained with Mulliken and Löwdin reflect a large dependence on the level of theory of choice, whereas those obtained with natural bond orbital show larger consistency across methodologies. Predicted stability across the actinide series calculated with coupled cluster with perturbative doubles and triples at the triple ζ level is equivalent to the one obtained when extrapolated to the complete basis set limit. The ground state of [Fm(NO3)]2+ and [Md(NO3)]2+ is predicted to have an electronic structure corresponding to An III state in gas and An IV in aqueous phase, whereas the ground state of [An(NO3)]2+ (with An = Ac to Es, Lr) presents an electronic structure corresponding to An IV in the gas and aqueous phase. The compounds studied with No in gas and aqueous phase present a preferred No III state, and the Lr compounds did not follow trends predicted for the rest of the actinide series, as previously observed in studies regarding its unusual electronic structure relative to its position in the periodic table.

Inner versus outer sphere metal-monoamide complexation: ramifications for tetravalent & hexavalent actinide selectivity

Extraction of tetravalent and hexavalent plutonium by straight and branched chained monoamides was studied using UV-vis spectroscopy. These results suggest straight monoamides recover outer-sphere species, while branched chain monoamides recover inner-sphere species.