Browsing by Author "Veliscek-Carolan, J"
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- Item131I discharges to the marine environment and uptake by algae in Sydney, Australia(South Pacific Radioactivity Association, 2008-11-25) Veliscek-Carolan, J; Hughes, CE; Hoffmann, EL; Loosz, TThe use of radiopharmaceuticals in nuclear medicine results in radioactive material being discharged to the sewer as human waste. Treated sewage effluent is in turn discharged to the marine environment through coastal and deepwater outfalls. 131l is the dominant medical isotope discharged to the environment as treatment doses can be large (up to 8 GBq) and excretion from patients is rapid. Also, 131l has a half life (8.04 days), which is significantly greater than the effluent residence time in the sewerage system (< 1 day), and a low Kd resulting in a low removal during treatment. 131l levels from <1 to 150 Bq/L have been measured in effluent from Sydney sewage treatment plants. Following discharge of effluent to ocean outfalls, 131l levels in the seawater are likely to be low as a result of dispersion and dilution of the effluent. However, 131I is easily detected in macroalgae growing near coastal outfalls as the algae bio-accumulate iodine. In fact, 131I levels between 1 and 375 Bq/kg have been observed in various macroalgae species near the outfall from Cronulla sewage treatment plant in Sydney, since November 1995. This paper presents data on 131l levels in effluent and uptake by algae growing near shoreline outfalls in the Sydney region. Radiation doses to marine biota from 131l discharged to coastal waters are calculated to be very small and below the ERICA screening level of l0 uGy/hr. Human dose assessment is also discussed.
- ItemCeramic conversion and densification of zirconium phosphonate sorbent materials(Elsevier, 2018-04-01) Veliscek-Carolan, J; Thorogood, GJ; Gregg, DJ; Tansu, M; Hanley, TLThe simple conversion of zirconium phosphonate sorbent materials, with known affinity for lanthanide elements, to durable ceramic waste forms via thermal treatment has been demonstrated. The use of zirconium phosphonate enables both removal of targeted elements from spent nuclear fuel and immobilisation into leach resistant solid products to be achieved using a single material. Thermal conversion was performed on the zirconium phosphonate both before and after loading with europium, which acted as a surrogate for the chemically similar minor actinides. Without europium loaded, the zirconium phosphonate sorbent formed predominantly KZr2(PO4)3 upon heating, independent of the processing conditions used. A maximum relative density of 87% was achieved with cold isostatic pressing (200 MPa) and sintering at 1200 °C for 12 h. When the zirconium phosphonate sorbent was loaded with europium, the phase composition formed upon thermal treatment was more complex. Specifically, mixtures of ZrP2O7, Eu0.33Zr2(PO4)3, EuPO4 and Zr2O(PO4)2 were formed, with phase compositions depending on the temperatures and pressures used. The simplest phase composition for the europium loaded material was achieved via uniaxial pressing (120 MPa) and sintering at 1300 °C for 1 h, although the ceramic pellet produced under these conditions had a relative density of only 53%. The loaded europium deported primarily to a EuPO4 phase, which is known to be highly stable and leach resistant. As such, these zirconium phosphonate materials have potential utility for treatment of nuclear wastes. © 2019 Elsevier B.V.
- ItemDose assessment for marine biota and humans from discharge of 131I to the marine environment and uptake by algae in Sydney, Australia.(South Pacific Environmental Radioactivity Association, 2008-11-24) Veliscek-Carolan, J; Hughes, CE; Hoffmann, ELIodine-131 reaches the marine environment through its excretion to the sewer by nuclear medicine patients followed by discharge through coastal and deepwater outfalls. (131)I has been detected in macroalgae, which bio-accumulate iodine, growing near the coastal outfall of Cronulla sewage treatment plant (STP) since 1995. During this study, (131)I levels in liquid effluent and sludge from three Sydney STPs as well as in macroalgae (Ulva sp. and Ecklonia radiata) growing near their shoreline outfalls were measured. Concentration factors of 176 for Ulva sp. and 526 for E. radiata were derived. Radiation dose rates to marine biota from (131)I discharged to coastal waters calculated using the ERICA dose assessment tool were below the ERICA screening level of 10muGy/hr. Radiation dose rates to humans from immersion in seawater or consumption of Ulva sp. containing (131)I were three and two orders of magnitude below the IAEA screening level of 10muSv/year, respectively.
- ItemEffective Am(III)/Eu(III) separations using 2,6-bis(1,2,4-triazin-3-yl)pyridine (BTP) functionalised titania particles and hierarchically porous beads(Royal Society of Chemistry, 2015-06-12) Veliscek-Carolan, J; Jolliffe, KA; Hanley, TLHybrid materials which selectively extract Am(III) over Eu(III) from 0.01 M nitric acid solutions with fast kinetics and separation factors up to 160 have been synthesised. The materials consist of titania functionalised with a modified organic 2,6-bis(1,2,4-triazin-3-yl)pyridine (BTP) derivative. Both particles and hierarchically porous beads have been prepared and provide advantages over conventional solvent extraction separations. © 2015 The Royal Society of Chemistry
- ItemEffects of precursor solution aging and other parameters on synthesis of ordered mesoporous titania powders(American Chemical Society, 2015-03-11) Veliscek-Carolan, J; Knott, RB; Hanley, TLEvaporation-induced self-assembly (EISA) of ordered mesoporous titania powders using block copolymer templates Brij 58 and F127 has been studied as a function of the precursor solution composition and age as well as the evaporation conditions. Small-angle X-ray scattering was used to monitor the degree of order in the mesoporous structure of materials synthesized under these varying conditions. Also, for the first time, the time-dependent formation of Ti structures in precursor solutions and the effect of those structures on the creation of mesostructural order have been demonstrated. The interactions of the Ti precursor with Brij 58 and F127 were investigated and showed that the different templates caused formation of Ti oligomers of unique sizes and structures. Precursor solution composition and evaporation conditions were also shown to affect the order and stability of the mesoporous titania produced. Overall, this systematic study has provided fundamental insights into the synthesis conditions that maximize the degree of order and thermal stability of the final materials. These “optimal” conditions are highly dependent on the choice of template. As a result of this improved understanding, the synthesis of ordered mesoporous titania powders using the block copolymer F127 as a template has been achieved without the use of stabilizing agents for the first time. © 2015 American Chemical Society
- ItemThe impact of structural variation in simple lanthanide binding peptides(Royal Society of Chemistry, 2016-08-03) Veliscek-Carolan, J; Hanley, TL; Jolliffe, KAA series of di-, tri- and tetra-peptides were synthesised using L- and D-glutamic acid in order to determine the effects of peptide length and stereochemistry on lanthanide binding affinity. Binding studies with Eu were performed at neutral pH, which is relevant to biological applications, and also under industrially relevant acidic conditions. Increasing peptide length resulted in higher binding affinity but the effect of stereochemistry was dependent on the peptide length. Modelling and experimental characterisation of the peptide[thin space (1/6-em)]:[thin space (1/6-em)]Eu complexes formed suggested that multiple modes of binding were present, with the Eu cation coordinated by the terminal and side chain carboxylic acids of the peptides as well as by backbone carbonyl groups. The peptide with the strongest binding affinity was the tetra-peptide with alternating L- and D-glutamic acid residues, which was able to bind Eu at pH values as low as 4. This peptide was appended with a long-chain alkene and used to covalently functionalise titania nanoparticles. The resulting peptide functionalised titania demonstrated selective sorption of lanthanides over Ca, Ni, Sr and Cs ions. Overall, a deeper understanding of how peptide structure affects lanthanide binding affinity has been gained and the potential of these peptides as selective ligands for separations at acidic pH has been demonstrated. © 2016 The Royal Society of Chemistry
- ItemNanoporous zirconium phosphonate materials with enhanced chemical and thermal stability for sorbent applications(American Chemical Society, 2020-04-01) Veliscek-Carolan, J; Rawal, A; Oldfield, DT; Thorogood, GJ; Bedford, NMNanoporous zirconium phosphonate (ZrP) materials are considered to be promising candidates for practical applications such as catalysis and separation, in particular because of their excellent stability, resulting from the strength of the P–O–Zr bond. However, the functionality of ZrP materials is dependent on the availability of free phosphonate groups uncoordinated by zirconium, the presence of which can decrease the stability. The mechanisms by which nanoporous ZrP materials degrade and lose functionality during thermal and chemical treatment are not well understood. Herein, we address this knowledge gap using nanoporous zirconium aminotris(methylenephosphonic acid) (Zr-ATMP) sorbent materials. Thermal treatment up to 150 °C caused collapse of the nanoporous structure of some Zr-ATMP materials without a significant effect on the chemical structure. On the other hand, contact with 5 M nitric acid changed the chemical structure of the Zr-ATMP materials by catalyzing the formation of P–O–Zr bonds and elemental leaching. Enhancement of the thermal and chemical stability of the Zr-ATMP materials was achieved by decreasing the pH of the synthesis and, interestingly, changing the counterion of the hydroxide used to control the pH also impacted the structure and stability of the resulting materials. The most stable Zr-ATMP material was produced at pH 3 using LiOH, but this material demonstrated lower selectivity than other Zr-ATMP materials, which decreases its practicality for separation applications. The Zr-ATMP material synthesized at pH 3 with NaOH showed an optimal balance between the stability and sorption performance. The enhanced chemical and thermal stability of this material drastically improves its applicability for use in harsh environments, such as in the treatment of radioactive wastes. © 2020 American Chemical Society
- ItemNew materials for selective separations at the back end of the nuclear fuel cycle(University of Sydney, 2016) Veliscek-Carolan, JStorage and recycling of nuclear waste are important issues that will increase in importance if nuclear power becomes more widely adopted worldwide. Recycling of used nuclear fuel is of benefit both in terms of increasing the nuclear lifetime (ie the number of years nuclear power will be a viable option for power generation) and decreasing the hazards (radiotoxicity, volume and longevity) of nuclear waste. Currently, most reprocessing of used nuclear fuel is performed using liquid-liquid extraction. However, use of solid sorbent materials has many advantages such the lack of organic solvent wastes. This research involves development of materials that are able to selectively remove specific target elements from solutions of used nuclear fuel. Once loaded with radionuclides, these materials may be utilised as transmutation matrices or wasteforms. Therefore, radiolytically and hydrolytically stable materials able to withstand the conditions of nuclear separations, such as titania and zirconia, have been targeted. Further, ordered porosity has been introduced into these titania and zirconia framework materials to improve their sorption capacity and kinetics. In order to impart selectivity to these materials, organic ligands are incorporated. Functional groups, including phosphonates, amines and peptides, have been chosen or designed based on their selectivity for elements relevant to the nuclear fuel cycle. Elements of interest include uranium, which constitutes >96% of used nuclear fuel and can be recycled; minor actinides, which contribute significantly to the radiotoxicity of nuclear waste and can also be recycled in fast neutron reactors; and lanthanides, which are targets for separation from the minor actinides as their high neutron absorption cross sections prevent transmutation of the minor actinides. Novel hybrid materials have been synthesized and their sorption characteristics, including selectivity, capacity and kinetics, evaluated. © 2016 The Author.
- ItemSelective sorption of actinides by titania nanoparticles covalently functionalized with simple organic ligands(American Chemical Society, 2012-11-01) Veliscek-Carolan, J; Jolliffe, KA; Hanley, TLAlthough current and proposed reprocessing of used nuclear fuel is performed predominantly by solvent extraction processes, solid phase sorbent materials have many advantages including the ability to avoid production of large volumes of organic waste. Therefore, three titania nanoparticle based sorbent materials have been developed, functionalized with organic ligands designed to impart selectivity for elements relevant to important separations at the back end of the nuclear fuel cycle. A novel, simplified method of covalent functionalization to the titania surface has been utilized, and the resulting materials have been shown to be hydrolytically stable at pH 2. The sorption behavior of these organofunctionalized titania materials was investigated over a wide pH range with a selection of elements including fission products and actinides. Titania nanoparticles functionalized with an amine or phosphate moiety were able to demonstrate exclusive extraction of uranium under optimized conditions. Titania nanoparticles functionalized with a picolinamide moiety exhibited superior minor actinide sorption properties, in terms of both efficiency and selectivity, to solvent extraction processes using similar organic moieties. As such, organo-functionalized titania materials as solid phase sorbents show promise as a future alternative to solvent extraction processes for nuclear separations. © 2013, American Chemical Society.
- ItemSeparation of actinides from spent nuclear fuel: a review.(Elsevier B.V., 2016-11-15) Veliscek-Carolan, JThis review summarises the methods currently available to extract radioactive actinide elements from solutions of spent nuclear fuel. This separation of actinides reduces the hazards associated with spent nuclear fuel, such as its radiotoxicity, volume and the amount of time required for its’ radioactivity to return to naturally occurring levels. Separation of actinides from environmental water systems is also briefly discussed. The actinide elements typically found in spent nuclear fuel include uranium, plutonium and the minor actinides (americium, neptunium and curium). Separation methods for uranium and plutonium are reasonably well established. On the other hand separation of the minor actinides from lanthanide fission products also present in spent nuclear fuel is an ongoing challenge and an area of active research. Several separation methods for selective removal of these actinides from spent nuclear fuel will be described. These separation methods include solvent extraction, which is the most commonly used method for radiochemical separations, as well as the less developed but promising use of adsorption and ion-exchange materials. This review summarises the methods currently available to extract radioactive actinide elements from solutions of spent nuclear fuel. This separation of actinides reduces the hazards associated with spent nuclear fuel, such as its radiotoxicity, volume and the amount of time required for its’ radioactivity to return to naturally occurring levels. Separation of actinides from environmental water systems is also briefly discussed. The actinide elements typically found in spent nuclear fuel include uranium, plutonium and the minor actinides (americium, neptunium and curium). Separation methods for uranium and plutonium are reasonably well established. On the other hand separation of the minor actinides from lanthanide fission products also present in spent nuclear fuel is an ongoing challenge and an area of active research. Several separation methods for selective removal of these actinides from spent nuclear fuel will be described. These separation methods include solvent extraction, which is the most commonly used method for radiochemical separations, as well as the less developed but promising use of adsorption and ion-exchange materials. © 2016 Elsevier B.V.
- ItemZirconium organophosphonates as high capacity, selective lanthanide sorbents(Elsevier, 2014-05-29) Veliscek-Carolan, J; Hanley, TL; Luca, VNovel and versatile zirconium organophosphonate coordination networks have been developed as sorbent platforms via simple, low-temperature hydrothermal reactions of zirconium propoxide with amino tris(methylene phosphonic acid) (ATMP). The resulting materials exhibited hierarchical porosity and possessed exceptional selectively for lanthanide elements over mono- and divalent metal ions during competitive sorption experiments in 0.1 M HNO3, as well as modest intra-lanthanide selectivity. As such, the present materials have potential as solid phase extractants for lanthanide separations in applications including mining, radioactive waste treatment and environmental remediation. Lanthanide sorption was shown to occur via uncoordinated Psingle bondO groups in the ATMP molecule. The structure, porosity and sorption properties of the coordination network platform could be tuned through varying the molar ratio of phosphorus to zirconium. Interestingly, the sample with the lowest surface area (<2 m2/g) demonstrated the highest sorption capacity. Optimal compositions demonstrated europium sorption with fast kinetics and very high capacities of up to 0.63 g/mg min and 60 mg/g respectively. As such, these highly stable zirconium organophosphonates, prepared from inexpensive precursor chemicals using one-pot methods, perform comparably to costly commercially available polymer resins. © 2014, Elsevier B.V.