Copper nanoparticles (Cu‐NPs) have a wide range of applications as heterogeneous catalysts. In this study, a novel green biosynthesis route for producing Cu‐NPs using the metal‐reducing bacterium, Shewanella oneidensis is demonstrated. Thin section transmission electron microscopy shows that the Cu‐NPs are predominantly intracellular and present in a typical size range of 20–40 nm. Serial block‐face scanning electron microscopy demonstrates the Cu‐NPs are well‐dispersed across the 3D structure of the cells. X‐ray absorption near‐edge spectroscopy and extended X‐ray absorption fine‐structure spectroscopy analysis show the nanoparticles are Cu(0), however, atomic resolution images and electron energy loss spectroscopy suggest partial oxidation of the surface layer to Cu2O upon exposure to air. The catalytic activity of the Cu‐NPs is demonstrated in an archetypal “click chemistry” reaction, generating good yields during azide‐alkyne cycloadditions, most likely catalyzed by the Cu(I) surface layer of the nanoparticles. Furthermore, cytochrome deletion mutants suggest a novel metal reduction system is involved in enzymatic Cu(II) reduction and Cu‐NP synthesis, which is not dependent on the Mtr pathway commonly used to reduce other high oxidation state metals in this bacterium. This work demonstrates a novel, simple, green biosynthesis method for producing efficient copper nanoparticle catalysts.

General ConsiderationsCaution: 254 Es (t 1/2 = 275.7 days, 70.9 TBq g −1 ) and 249 Cf (t 1/2 = 351 years, 150 GBq g −1 ) are highly radioactive, and decay to α-, β-and γ-emitting isotopes. These isotopes and their decay daughters present substantial health risks, and were manipulated only in facilities specifically designed for the safe handling of long-lived radioactive materials. All measurements were taken in controlled facilities and/or using multiple containment procedures.

Mud Hills clinoptilolite has been used in an effluent treatment plant (SIXEP) at the Sellafield nuclear reprocessing site. This material has been used to remove 134/137Cs and 90Sr successfully from effluents for 3 decades. Samples of the zeolite have been tested in column experiments to determine their ability to remove radioactive Cs+ and Sr2+ ions under increasing concentrations of competing ions, Ca2+, Mg2+, Na+ and K+. These ions caused increased elution of Cs+ and Sr2+. Ca2+, Mg2+ and K+ were more effective competitors than Na+. For Na+, it was found that if concentration was reduced, then column performance recovered rapidly.Electronic supplementary materialThe online version of this article (10.1007/s10967-018-6329-8) contains supplementary material, which is available to authorized users.

The behaviour of U(VI) in hyperalkaline fluid/calcite systems was studied over a range of U(VI) concentrations (5.27×10-5μM to 42.0μM) and in two high pH systems, young and old synthetic cement leachate in batch sorption experiments. These systems were selected to be representative of young- (pH 13.3) and old-stage (pH 10.5) leachate evolution within a cementitious geological disposal facility. Batch sorption experiments, modelling, extended X-ray absorption fine structure spectroscopy, electron microscopy, small angle X-ray scattering and luminescence spectroscopy were used to define the speciation of U(VI) across the systems of study. At the lowest concentrations (5.27×10-5μM 232U(VI)) significant U removal was observed for both old and young cement leachates, and this was successfully modelled using a first order kinetic adsorption modelling approach. At higher concentrations (>4.20μM) in the young cement leachate, U(VI) showed no interaction with the calcite surface over an 18month period. Small angle X-ray scattering techniques indicated that at high U concentrations (42.0μM) and after 18months, the U(VI) was present in a colloidal form which had little interaction with the calcite surface and consisted of both primary and aggregated particles with a radius of 7.6±1.1 and 217±24Å, respectively. In the old cement leachate, luminescence spectroscopy identified two surface binding sites for U(VI) on calcite: in the system with 0.21μM U(VI), a liebigite-like Ca2UO2(CO3)3 surface complex was identified; at higher U(VI) concentrations (0.42μM), a second binding site of undetermined coordination was identified. At elevated U(VI) concentrations (>2.10μM) in old cement leachate, both geochemical data and luminescence spectroscopy suggested that surface mediated precipitation was controlling U(VI) behaviour. A focused ion beam mill was used to create a section across the U(VI) precipitate-calcite interface. Transmission electron microscope images of the section revealed that the calcite surface was coated with a nano crystalline, U containing phase. Selected area electron diffraction images of the U precipitate which was formed at a U(VI) concentration of 4.20μM were consistent with the formation of calcium uranate. XAS spectroscopy at higher concentrations (≥21.0μM) suggested the formation of a second U(VI) phase, possibly a uranyl oxyhydroxide phase. These results indicated that in the young cement leachate, U(VI) did not react with the calcite surface unless U(VI) concentrations were very low (5.27×10-5μM). At higher concentrations, speciation calculations suggested that U(VI) was significantly oversaturated and experimental observations confirmed it existed in a colloidal form that interacted with the mineral surface only weakly. In the old cement leachate systems at low concentrations batch sorption and luminescence data suggested that U(VI) removal was being driven by a surface complexation mechanism. However, at higher concentrations, spectroscopic methods suggest a combination of both surface complexation and ...