Browsing by Author "Soldenhoff, KH"

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    Beneficial effect of iron oxide/hydroxide minerals on sulfuric acid baking and leaching of monazite
    (Elsevier B. V., 2022-05) Demol, J; Ho, E; Soldenhoff, KH; Karatchevtseva, I; Senanayake, G
    The sulfuric acid bake/leach process is an established industrial process for the extraction of rare earths from hard-rock monazite ores/concentrates. The chemical reactions in the monazite acid bake can be strongly influenced by the gangue mineralogy of the ore/concentrate. In this work, the beneficial effect of three iron oxide/hydroxide minerals, namely hematite, goethite and magnetite, added to high grade monazite concentrate in the acid bake (temperature range of 200–800°) and leach process was investigated to understand the role of iron gangue. Baked solids and leach residues were characterised by elemental analyses, XRD, SEM-EDS and FT-IR. It was found that the addition of iron minerals to the monazite acid bake had a significant impact on bake chemistry, acting to significantly increase the leaching of both the rare earth elements and thorium, compared to monazite alone, mainly for temperatures above 300 °C. The increased dissolution of rare earth elements and thorium was attributed to the formation of an amorphous and insoluble iron sulfate-polyphosphate type phase in preference to insoluble rare earth and thorium containing polyphosphates identified during acid baking of monazite alone. After baking at 650 °C, the iron sulfate-polyphosphate type phase was altered to a more soluble form, leading to an increase in dissolution of iron, phosphorus and thorium. Acid baking at 800 °C led to the formation of FePO4, Fe2O3, CePO4 (monazite) and in some cases CeO2, causing a decrease in leaching of rare earths and thorium, and either an increase or a decrease in leaching of iron and phosphorus depending on the formation of FePO4 versus Fe2O3. Crown Copyright © 2022 Published by Elsevier B. V.
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    Corrigendum to “Application of chelating weak base resin Dowex M4195 to the recovery of uranium from mixed sulfate/chloride media” [Chem. Eng. J., 317 (2017) 80–89]
    (Elsevier, 2017-09-15) Ogden, MD; Moon, EM; Wilson. A; Griffith, CS; Mata, JP; Soldenhoff, KH; Pepper, SE
    The authors regret that the historical contributions from collaborators at ANSTO were not sufficiently acknowledged in this paper. The authors would like to add the following contributors, with the affiliations shown above. The acknowledgements should also state the following; “The authors would like to acknowledge the members of the Separations and Nuclear Chemical Engineering Research (SNUCER) group at the University of Sheffield who all assisted with this work in some capacity. Thank you to Prof. Neil Hyatt and Dr. Claire Corkhill in MIDAS, University of Sheffield for use of analytical equipment. Thank you to Dr. Gabriella Kakonyi at the Kroto Research Institute at the University of Sheffield for ICP-MS analysis. Funding was provided by the Department of Chemical and Biological Engineering at The University of Sheffield, as part of their start-up scheme. This work is published with the permission of the Australian Nuclear Science & Technology Organisation, where most of the work was conducted.” The authors would like to apologise for any inconvenience caused. © 2017 Elsevier B.V
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    Hydrodynamic characterisation of hollow fibre modules for liquid-liquid extraction
    (The Institution of Australian Engineers, 1999-09-26) McCulloch, JK; Macnaughton, SJ; Soldenhoff, KH
    Liquid-liquid extraction in hollow fibre contactors has been widely investigated in recent years. These techniques have a number of advantages over conventional solvent extraction, where the phases are dispersed; solvent losses due to entrainment and separation problems are avoided, there are no density constraints on the organic phase, the flow rates of each phase may be varied independently, and the system can be efficiently operated under non-equilibrium conditions. The hollow fibre membranes used in these processes are generally housed in modules of a shell and tube configuration and thorough characterisation of the hollow fibre modules, including hydrodynamic behaviour and the effects of fibre swelling and packing density is required. Swelling occurs in a range of solvents, and will affect the interfacial area and hydrodynamics of the module, which in turn influences the overall mass transfer performance. In this study, modules containing microporous polypropylene hollow fibres (600 mum i.d.) were constructed with fibre packing densities ranging from 18 % to 64 %. The influence of fibre swelling and packing density on hydrodynamic performance was investigated and where possible correlated with published theory. The consequences of the observed behaviour are discussed in terms of mass transfer within the HFCLM process.
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    The potential for uranium recovery at Nolans
    (ALTA Metallurgical Services, 2007-05-24) Soldenhoff, KH; Ho, E; Mackowski, S
    The Nolans deposit, owned by Arafura Resources, Ltd, is located near Aileron in the Northern Territory of Australia. Initial rare earth mineralisation was detected in 1995, which was confirmed by further exploration work carried out from 1999 onwards. The rare earths are predominantly concentrated as rare earth phosphates, hosted by fluorapatite and cheralite. An essential part of the mineral chemistry of apatite (Ca5(PO4)3(F,OH)), is that the calcium phosphate structure does allow some substitution by rare earths and other ions, including uranium ions. Current mineral resources at Nolans, using a 1% REE cut-off grade, are 18.6 million tonnes at 3.1% rare earth oxide, 14.0% P205 and 0.021% U308. This resource can support a 10,000 tla REO operation for at least 20 years. The concentration of uranium in Nolans is higher than is typical of phosphate rock deposits worldwide. This requires appropriate management of the radioactivity during ore processing, but also provides an opportunity for recovery of uranium as a by-product. The recovery must be integrated into the rare earth process, which is the primary focus of the project. Furthermore, the separation of rare earths from the phosphate matrix and the recovery of phosphoric acid or other fertiliser products is also an important consideration. This paper discusses the various process options that are being considered for the development of a process for Nolans that integrates the recovery of phosphate values and uranium as by-products of rare earth processing. © The Authors
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    Solvent extraction of rare earth elements using phosphonic/phosphinic acid mixtures
    (Elsevier B.V., 2015-10-01) Quinn, JE; Soldenhoff, KH; Stevens, GW; Lengkeek, NA
    This work examines the extraction of rare earths (Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Yb, Lu and Y) by 2-ethylhexyl phosphonic acid 2-ethylhexyl mono-ester (EHEHPA), Cyanex 272, Cyanex 572 and mixtures of EHEHPA and Cyanex 272, to determine whether the mixed extractants could be beneficial to industrial rare earth separations. Analysis of the effect of pH and extractant concentration on distribution ratios indicated that addition of the phosphinic acid to EHEHPA resulted in an antagonistic effect. The antagonistic effect was confirmed using the method of continuous variation, and is thought to be due to an association between the phosphinic and phosphonic acids which reduces the free dimer concentrations of each component. Examination of 31P{1H} NMR spectra showed that for the mixed extractant the extracted yttrium complex was predominantly composed of EHEHPA. However, some Cyanex 272 was also found to be associated with yttrium, which suggests the formation of a mixed yttrium–EHEHPA–Cyanex 272 complex. Separation factors for the mixed extractants were similar to those of EHEHPA, while the maximum loading for equimolar extractants was approximately halved. The results suggest potential savings resulting from a reduction in the stripping acid required for the mixed extractant relative to equimolar EHEHPA; however equipment size would likely increase due to lower overall metal loading. © 2015 Elsevier B.V.