Browsing by Author "Aly, Z"

Now showing 1 - 16 of 16
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    Aqueous dissolution and immobilisation potential of geopolymers for radioactive ions
    (Materials Australia, 2007-07-02) Vance, ER; Perera, DS; Aly, Z
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    Aqueous leachability of geopolymers containing cations Ag, Cd, and Co
    (The Italian Ceramic Society, 2008-06-29) Perera, DS; Aly, Z; Davis, J; Kurlapski, I; Vance, ER
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    Aqueous leachability of metakaolin-based geopolymers with molar ratios of Si/Al=1.5-4
    (Materials Australia, 2007-07-04) Aly, Z; Davis, J; Vance, ER; Perera, DS; Durce, D; Hanna, JV
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    Aqueous leachability of metakaolin-based geopolymers with molar ratios of Si/Al=1.5-4
    (Elsevier, 2008-08-31) Aly, Z; Vance, ER; Perera, DS; Hanna, JV; Griffith, CS; Davis, J; Durce, D
    The leachability in water of metakaolin based geopolymers with molar ratios of Na/Al = 1 and Si/Al = 1.5-4.0 has been investigated in order to optimise the composition for the immobilisation of nuclear waste. Formulations with Si/Al of around 2 are the most suitable using the ASTM/PCT leach test method. The variability of the leach results is discussed with reference to the microstructure, compressive strength and the degree of polymerisation of the geopolymers as observed here by solid state nuclear magnetic resonance, XRD and infrared measurements. © 2008, Elsevier Ltd.
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    Feasibility of incorporating cations and anions expected in radioactive waste streams in metakaolin-based geopolymers.
    (Electrical Components International, 2007-03-25) Perera, DS; Vance, ER; Aly, Z; Fuchs, A; Kiyama, S; Davis, J; Smith, SV
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    Geopolymers as candidates for low/intermediate level highly alkaline waste.
    (Materials Research Society, 2006-11-27) Perera, DS; Vance, ER; Kiyama, S; Aly, Z; Yee, P
    Geopolymers should be serious waste form candidates for intermediate level waste (ILW), insofar as they are more durable than Portland cement and can pass the PCT-B test for high-level waste. Thus an alkaline ILW could be considered to be satisfactorily immobilised in a geopolymer formulation. However a simulated Hanford tank waste was found to fail the PCT-B criterion even for a waste loading as low as 5 wt%, very probably due to the formation of a soluble sodium phosphate compound(s). This suggests that it could be worth developing a ìmixedî GP waste form in which the amorphous material can immobilise cations and a zeolitic component to immobilise anions. The PCTñB test is demonstrably subject to significant saturation effects, especially for relatively soluble waste forms.
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    Geopolymers for low-level waste immobilization
    (American Ceramic Society, 2006-10-15) Vance, ER; Blackford, MG; Hanna, JV; Aly, Z; Perera, DS
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    Hot isostatically pressed (HIPed) fluorite glass‐ceramic wasteforms for fluoride molten salt wastes
    (John Wiley & Sons, Inc., 2020-06-07) Gregg, DJ; Vance, ER; Dayal, P; Farzana, R; Aly, Z; Holmes, R; Triani, G
    Molten pyroprocessing salts can be used to dissolve used nuclear fuel from a reactor allowing recovery of the actinides. Previously, ANSTO have demonstrated hot isostatically pressed (HIPed) sodalite glass‐ceramic wasteforms for eutectic (Li,K)Cl salts containing fission products, but this system cannot be used for the analogous molten alkali fluoride salts (eg, FLiNaK), which have utility in the application of the next generation of nuclear reactors. In this work, a novel glass‐ceramic composite wasteform has been prepared by HIPing, as a candidate for the immobilization of fission product‐bearing FLiNaK salts. The wasteform has been tailored to immobilize the high fluoride content of the waste within fluorite, whereas the waste alkali elements are incorporated in a durable sodium aluminoborosilicate glass, with total waste loadings of ~17‐21 wt% achieved. It was also demonstrated that the speciation of Mo‐ and Sb‐simulated fission products was altered by adding Ti metal due to a controlled redox environment. The resulting candidate wasteform has been studied by X‐ray diffraction and scanning electron microscopy, including the HIP canister‐wasteform interaction zone, and its performance assessed via leaching studies using the PCT and ASTM C1220 leaching protocols. Dr Vance very much enjoyed the challenge of wasteform design for problematic nuclear wastes, for which fission product‐bearing FLiNaK salts are a clear example. His ability to hone in on a wasteform solution with viable waste loadings that meet performance requirements was testament to his nearly 40 years experience in nuclear waste immobilization. The samples discussed in this work represent the last wasteform materials that he prepared. © 1999-2020 John Wiley & Sons, Inc.
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    Immobilisation of cations and anions in geopolymers
    (Materials Science and Technology (MS&T), 2007-09-16) Vance, ER; Perera, DS; Aly, Z; Walls, P; Zhang, YJ; Cassidy, DJ; Griffith, CS
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    Immobilization of iodine via copper iodide
    (Elsevier, 2018-07) Vance, ER; Grant, C; Karatchevtseva, I; Aly, Z; Stopic, A; Harrison, JJ; Thorogood, GJ; Wong, HKY; Gregg, DJ
    CuI is a candidate wasteform for the immobilization of the fission product 129I. CuI can be made simply by the addition of CuCl to an I− bearing solution such that exchange of Cl− with I− takes place. The CuI material can then be consolidated into a wasteform by sintering at approximately 550 °C in argon or by hot isostatically pressing at 550 °C with 100 MPa of pressure. A waste loading of greater than 60 wt.% is achievable with good water leach resistance, in keeping with the low solubility product of CuI. However, like the well known wasteform candidate AgI, CuI decomposes in water containing metallic Fe. To compensate this deficiency, the sintered CuI wasteform can be further protected by surrounding it by Sn powder and HIPing at the low temperature of 200 °C. © 2018 Elsevier B.V
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    Pyrochlore glass-ceramics for the immobilization of molybdenum-99 production wastes: demonstrating scalability and flexibility to waste stream variance
    (Elsevier, 2021-11) Farzana, R; Zhang, YJ; Dayal, P; Aly, Z; Holmes, R; Triani, G; Vance, ER; Gregg, DJ
    Pyrochlore glass ceramics have been fabricated via in-situ crystallization under reducing conditions by both sintering and hot isostatic pressing (HIPing) as candidate wasteforms for the acidic waste biproduct of Mo-99 radiopharmaceutical production. The tailored wasteform demonstrates flexibility in the wasteform design to receive the required waste variability, it also suitably passes high-level waste performance requirement, and successfully scales to 1 kg scale with 45 wt.% waste loading. U-rich pyrochlore as the major phase was confirmed by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, with residual glass and minor secondary phases. The presence of both U4+ and U5+ valences in the wasteforms was revealed by diffuse reflectance spectroscopy. Addition of glass content had little influence on the pyrochlore composition but facilitated minor perovskite formation. The up-scaled dense, HIPed sample showed elemental releases of < 2 g/L for all elements in durability experiments. © 2021 Elsevier Ltd
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    Removal of aluminium from aqueous solutions using PAN-based adsorbents: characterisation, kinetics, equilibrium and thermodynamic studies
    (Springer, 2014-12-04) Aly, Z; Graulet, A; Scales, N; Hanley, TL
    Economic adsorbents in bead form were fabricated and utilised for the adsorption of Al(3+) from aqueous solutions. Polyacrylonitrile (PAN) beads, PAN powder and the thermally treated PAN beads (250 °C/48 h/Ar and 600 °C/48 h/Ar-H2) were characterised using different techniques including Fourier transform infrared spectroscopy, X-ray diffraction, specific surface analysis (Brunauer-Emmett-Teller), thermogravimetric analysis as well as scanning electron microscopy. Effects of pH, contact time, kinetics and adsorption isotherms at different temperatures were investigated in batch mode experiments. Aluminium kinetic data best fit the Lagergren pseudo-second-order adsorption model indicating a one-step, surface-only, adsorption process with chemisorption being the rate limiting step. Equilibrium adsorption data followed a Langmuir adsorption model with fairly low monolayer adsorption capacities suitable for freshwater clean-up only. Various constants including thermodynamic constants were evaluated from the experimental results obtained at 20, 40 and 60 °C. Positive values of ΔH° indicated that the adsorption of Al(3+) onto all three adsorbents was endothermic with less energy input required for PAN powder compared to PAN beads and low-temperature thermally treated PAN. Negative ΔG° values indicated that the aluminium adsorption process was spontaneous for all adsorbents examined. © 2020 Springer Nature
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    The role of titanate ceramics in immobilisation of wastes arising from partitioning and weapons disposition
    (Japan Atomic Energy Research Institute (JAERI), 2002-03-01) Hart, KP; Zhang, YJ; Begg, BD; Aly, Z; Brownscombe, AJ; Day, RA; Stewart, MWA; Lumpkin, GR; Vance, ER; Jotsons, A
    The development of ceramics for the immobilisation of radioactive wastes has been on-going at ANSTO since 1980 and has involved collaboration with JAERI, the USDOE, LLNL and other international laboratories. This work has examined various processing routes, radiation damage effects and long-term aqueous durability for a range of titanate ceramics. Within these studies, information on the long-term behaviour of ceramics chosen to immobilities excess Pu and actinide-rich wastes arising from partitioning strategies have been obtained. Overall, the long-term durability, limitations on criticality under processing and disposal conditions and existence of viable natural analogues endorse the use of titanate ceramics for immobilisation of actinide-rich wastes. © 2002 Japan Atomic Energy Research Institute
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    Silver iodide sodalite – wasteform / HIP canister interactions and aqueous durability
    (Elsevier, 2019-04-15) Maddrell, ER; Vance, ER; Grant, C; Aly, Z; Stopic, A; Palmer, T; Harrison, JJ; Gregg, DJ
    The use of silver zeolite for the capture of radioiodine from the vapour phase, followed by thermal conversion now appears to be the most direct route by which a sodalite wasteform can be formed. In addition, consolidation by hot-isostatic pressing (HIP) in sealed canisters has many significant advantages over conventional methods such as sintering or melting these candidate wasteforms. The choice of HIP canister material is important as reaction at the wasteform/HIP canister interface results in an interaction zone that can potentially produce detrimental phases, wasteform porosity and canister thinning. This paper builds on a previous study that demonstrated that iodine could be captured from the vapour phase using silver exchanged zeolite and converted to sodalite by HIPing in Fe HIP canisters. The Cu or Ni metal HIP canisters used in this work result in an ∼100–200 μm thick local interaction zone with a variety of chemistries. Durability studies were conducted using a variety of reducing conditions and clearly demonstrated the redox sensitivity of silver sodalite. While the silver sodalite wasteform produced is, like the popular AgI-based wasteforms, highly leach resistant to leaching by deionised water it was unstable under highly reducing conditions, which are likely to occur in most geological disposal facilities. Post leaching characterisation revealed the redeposition of AgI and the formation of an aluminosilicate alteration layer under some leaching conditions. Appropriate precautions are required should a silver sodalite wasteform for iodine immobilisation be exposed to reducing groundwater conditions. Crown Copyright © 2019 Published by Elsevier B.V.
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    Uranium extraction from aqueous solution using dried and pyrolyzed tea and coffee wastes
    (Springer Netherlands, 2013-02-01) Aly, Z; Luca, V
    The adsorption of U(VI) onto dried and pyrolyzed tea and coffee wastes was investigated. The adsorption properties of the materials were characterized by measuring uranium uptake as a function of solution pH, kinetics and adsorption isotherms. pH profile of uranium adsorption where UO2 2+ is expected to be the predominant species was measured between pH 0 and 4. Both Langmuir and Freundlich adsorption models were used to describe adsorption equilibria, and corresponding constants evaluated. Using the Langmuir model, the maximum adsorption capacity of uranium by dried tea and coffee wastes was 59.5 and 34.8 mg/g, respectively at 291 K. Adsorption thermodynamic constants, ΔH° ΔS° and ΔG° were also calculated from adsorption data obtained at three different temperatures. Adsorption thermodynamics of uranyl ions on dried tea and coffee systems indicated spontaneous and endothermic processes. Additionally, a Lagergren pseudo-second-order kinetic model was used to fit the kinetic experimental data for both adsorbents and the constants evaluated. Dried tea and coffee wastes proved to be effective adsorbents with high capacities and significant advantage of a very low cost.© 2012, Akadémiai Kiadó, Budapest, Hungary.