Benchtop Zone Refinement of Simulated Future Spent Nuclear Fuel Pyroprocessing Waste.

The UK's adoption of pyroprocessing of spent nuclear fuel as an alternative to the current aqueous processing routes requires a robust scientific underpinning of all relevant processes. One key process is the clean-up of the contaminated salt from the electroreducing and electrorefining processes. A proposed method for this clean-up is zone refining, whereby the tendency of the contaminants to remain in the liquid phase during melting and freezing is exploited to 'sweep' the contaminants to one end of the sample. Experiments were performed, utilising off-the-shelf laboratory equipment, to demonstrate the feasibility of zone refining for clean-up of electroreducing and electrorefining wastes. This was successful for the electrorefining simulant samples, with effective segregation coefficient, keff, values, which provide a measure of the degree of separation in the sample, between 0 and 1. Lower values indicate greater separation, with values of as low as 0.542 achieved here, corresponding to a reduction in RECl3 content from 10.0 wt.% to 8.4 wt.% (for 80% salt reuse). Due to difficulties in obtaining a fully homogeneous electroreducing simulant waste, it was not possible to demonstrate the feasibility of zone refining using the current experimental setup. Further research is required to elucidate the correct preparation conditions for production of homogeneous electroreducing waste simulants.

Antimicrobial Fe2O3-CuO-P2O5 glasses.

Glasses with high antimicrobial efficacy were developed in the Fe2O3-CuO-P2O5 ternary system to mitigate fomite-mediated transmission of infectious diseases in high-risk settings such as hospitals, daycares, and nursing homes. Binary CuO-P2O5 glasses were not durable enough for use as high touch point articles, so Fe2O3 was added to the compositions to increase the chemical durability. The amount of Cu leachate decreased by at least 3 orders of magnitude when Fe2O3 was increased from 0 to 13.1 mol%. At the highest Fe2O3 contents and corresponding highest durability, the glass was no longer able to pass a test of antimicrobial efficacy with < 3 log kill compared to > 5 log kill for all other compositions. Ab-initio molecular dynamics simulations showed increasing bridging oxygen species at the expense of non-bridging oxygen species with the increase in Fe2O3 content, showing that the glasses exhibited increased chemical durability because they were more interconnected and structurally bound. Experimental results with glasses at fixed CuO and decreasing Fe2O3 confirmed that Fe2O3 content (not CuO) controlled the Cu release rate and, thus, the antimicrobial efficacy of the glasses. The significance of the oxidation state of the leached Cu was overwhelmed by the importance of the amount of Cu leachate.

An injectable, self-healing and MMP-inhibiting hyaluronic acid gel via iron coordination.

Regulating the activity of matrix metalloproteinases (MMPs) is a potential strategy for osteoarthritis (OA) therapy, although delivering this effect in a spatially and temporally localised fashion remains a challenge. Here, we report an injectable and self-healing hydrogel enabling factor-free MMP regulation and biomechanical competence in situ. The hydrogel is realised within 1 min upon room temperature coordination between hyaluronic acid (HA) and a cell-friendly iron-glutathione complex in aqueous environment. The resultant gel displayed up to 300% in shear strain and tolerance towards ATDC 5 chondrocytes, in line with the elasticity and biocompatibility requirements for connective tissue application. Significantly enhanced inhibition of MMP-13 activity was achieved after 12 h in vitro, compared with a commercial HA injection (OSTENIL® PLUS). Noteworthy, 24-hour incubation of a clinical synovial fluid sample collected from a late-stage OA patient with the reported hydrogel was still shown to downregulate synovial fluid MMP activity (100.0 ± 17.6% ➔ 81.0 ± 7.5%), with at least comparable extent to the case of the OSTENIL® PLUS-treated SF group (100.0 ± 17.6% ➔ 92.3 ± 27.3%). These results therefore open up new possibilities in the use of HA as both mechanically-competent hydrogel as well as a mediator of MMP regulation for OA therapy.

Structure and magnetism of the Rh4+-containing perovskite oxides La0.5Sr0.5Mn0.5Rh0.5O3 and La0.5Sr0.5Fe0.5Rh0.5O3.

Synchrotron X-ray powder diffraction data indicate that La0.5Sr0.5Mn0.5Rh0.5O3 and La0.5Sr0.5Fe0.5Rh0.5O3 adopt distorted perovskite structures (space group Pnma) with A-site and B-site cation disorder. A combination of XPS and 57Fe Mössbauer data indicate the transition metal cations in the two phases adopt Mn3+/Rh4+ and Fe3+/Rh4+ oxidation state combinations respectively. Transport data indicate both phases are insulating, with ρ vs. T dependences consistent with 3D variable-range hopping. Magnetisation data reveal that La0.5Sr0.5Mn0.5Rh0.5O3 adopts a ferromagnetic state below Tc ∼ 60 K, which is rationalized on the basis of coupling via a dynamic Jahn-Teller distortion mechanism. In contrast, magnetic data reveal La0.5Sr0.5Fe0.5Rh0.5O3 undergoes a transition to a spin-glass state at T ∼ 45 K, attributed to frustration between nearest-neighbour Fe-Rh and next-nearest-neighbour Fe-Fe couplings.

The facile and additive-free synthesis of a cell-friendly iron(iii)-glutathione complex.

The straightfoward creation of an unreported glutathione-stabilised iron(iii) complex is disclosed. In contrast to previous reports, glutathione was shown to coordinate and stabilise iron directly under physiological conditions in the absence of additional sulfur containing molecules, such as sodium sulfide. The complex was extensively characterised; the molecular geometry was determined as two inequivalent octahedra, approximately 2/3 of which are slightly distorted towards more tetrahedral in character, with the remaining 1/3 more regularly octahedral. The dispersion of the iron(iii)-glutathione complex in aqueous solution yielded particles of 255 ± 4 nm in diameter that enhanced the growth and proliferation of L929 fibroblast cells over 7 days, and inhibited the activity of matrix metalloproteinase-13. Consequently, the unprecedented glutathione-stabilised iron(iii) complex disclosed has potential use as a simple-to-prepare growth factor for inclusion within cell culture media, and is an excellent candidate as a therapeutic for the treatment of metalloproteinase-13-associated diseases.

Structure and properties of Na5FeSi4O12 crystallized from 5Na2O-Fe2O3-8SiO2 glass.

The phase Na5FeSi4O12 [pentasodium iron(III) silicate] crystallizes readily from the Na2O-Fe2O3-SiO2 glass system in a relatively large compositional range. However, its crystal structure and properties have not been studied in detail since its discovery in 1930. In this work, the Na5FeSi4O12 phase was crystallized from a host glass with 5Na2O·Fe2O3·8SiO2 stoichiometry, and both the glass and the crystal were studied. It was found that the Na5FeSi4O12 phase crystallizes at ∼720 °C from the glass and melts at ∼830 °C when heated at a rate of 10 °C min-1. The crystal structure was solved using single-crystal X-ray diffraction and the refined data are reported for the first time for the Na5FeSi4O12 phase. It exhibits trigonal symmetry, space group R-3c, with a = 21.418 and c = 12.2911 Å. The Na atoms located between adjacent structural channels exhibit positional disorder and splitting which was only refined by using low-temperature data collection (150 K). While ∼7% of the total Fe cations occur as Fe2+ in the glass, four-coordinated Fe3+ constitutes ∼93% of the total Fe cations. However, iron in the crystal, which exhibits a paramagnetic behavior, is solely present as six-coordinated Fe3+. The magnetic and vibrational properties of the glass and crystal are discussed to provide additional insight into the structure.

Complex Magnetic Ordering in the Oxide Selenide Sr2Fe3Se2O3.

Sr2Fe3Se2O3 is a localized-moment iron oxide selenide in which two unusual coordinations for Fe2+ ions form two sublattices in a 2:1 ratio. In the paramagnetic region at room temperature, the compound adopts the crystal structure first reported for Sr2Co3S2O3, crystallizing in space group Pbam with a = 7.8121 Å, b = 10.2375 Å, c = 3.9939 Å, and Z = 2. The sublattice occupied by two-thirds of the iron ions (Fe2 site) is formed by a network of distorted mer-[FeSe3O3] octahedra linked via shared Se2 edges and O vertices forming layers, which connect to other layers by shared Se vertices. As shown by magnetometry, neutron powder diffraction, and Mössbauer spectroscopy measurements, these moments undergo long-range magnetic ordering below TN1 = 118 K, initially adopting a magnetic structure with a propagation vector (1/2 - δ, 0, 1/2) (0 ≤ δ ≤ 0.1) which is incommensurate with the nuclear structure and described in the Pbam1 '( a01/2)000 s magnetic superspace group, until at 92 K ( TINC) there is a first order lock-in transition to a structure in which these Fe2 moments form a magnetic structure with a propagation vector (1/2, 0, 1/2) which may be modeled using a 2 a × b × 2 c expansion of the nuclear cell in space group 36.178 B a b21 m (BNS notation). Below TN2 = 52 K the remaining third of the Fe2+ moments (Fe1 site) which are in a compressed trans-[FeSe4O2] octahedral environment undergo long-range ordering, as is evident from the magnetometry, the Mössbauer spectra, and the appearance of new magnetic Bragg peaks in the neutron diffractograms. The ordering of the second set of moments on the Fe1 sites results in a slight reorientation of the majority moments on the Fe2 sites. The magnetic structure at 1.5 K is described by a 2 a × 2 b × 2 c expansion of the nuclear cell in space group 9.40 I a b (BNS notation).

Doped Sr2FeIrO6-Phase Separation and a Jeff ≠ 0 State for Ir5.

High-resolution synchrotron X-ray and neutron powder diffraction data demonstrate that, in contrast to recent reports, Sr2FeIrO6 adopts an I1̅ symmetry double perovskite structure with an a-b-c- tilting distortion. This distorted structure does not tolerate cation substitution, with low levels of A-site (Ca, Ba, La) or Fe-site (Ga) substitution leading to separation into two phases: a stoichiometric I1̅ phase and a cation-substituted, P21/ n symmetry, a-a-c+ distorted double perovskite phase. Magnetization, neutron diffraction, and 57Fe Mössbauer data show that, in common with Sr2FeIrO6, the cation substituted Sr2- xA xFe1- yGa yIrO6 phases undergo transitions to type-II antiferromagnetically ordered states at TN ∼ 120 K. However, in contrast to stoichiometric Sr2FeIrO6, cation substituted samples exhibit a further magnetic transition at TA ∼ 220 K, which corresponds to the ordering of Jeff ≠ 0 Ir5+ centers in the cation-substituted, P21/ n symmetry, double perovskite phases.