Browsing by Author "Wilson, A"

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    Application of chelating weak base resin Dowex M4195 to the recovery of uranium from mixed sulfate/chloride media
    (Elsevier, 2017-06-01) Ogden, MD; Moon, EM; Wilson, A; Pepper, SE
    The use of untreated seawater or bore water in uranium mineral processing circuits may represent a cheaper and more sustainable water resource for Australia’s mining operations. Using present technologies, the increased salinity from these water sources results in decreased uranium extraction and increased extraction of impurities. There is incentive to overcome these challenges, either through new technologies, or repurposing existing technologies. The ion exchange behaviour of U from sulfate media on the weakly basic chelating resin Dowex M4195 (bis-picolylamine functionality) and the effect of competing chloride and impurity metal ions (Th, Fe, Al, Cu, Ni) has been studied. Experiments to determine acid, and sulfate media behaviour, and extraction thermodynamics including the effect of increasing chloride concentration upon extraction behaviour were carried out. Dowex M4195 was found to have pK1 and pK2 values at 4.13 ± 0.04 and 2.1 ± 0.1 determined at 1.0 M NaCl. Dowex M4195 shows affinity for U(VI) over Fe3+ and Al3+ in sulfuric acid media with a U(VI) pH50 a full pH unit below that of Fe3+ at 0.17 and 1.82 respectively. With increasing chloride concentrations U and Th extraction is suppressed but Fe extraction increases. At the highest chloride concentrations explored Fe is preferentially extracted over U, and Th is not extracted at all. As chloride concentration increases the extraction of U passes through a minimum (40%) before increasing to around 60% for 4.0 M chloride at pH 1.80. Al3+ is not extracted by M4195 under any conditions explored. Dowex M4195 does show high selectivity for Cu and Ni over everything else. ©2017 Elsevier B.V
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    Impact of chloride on uranium(VI) speciation in acidic sulfate ion exchange systems: towards seawater-tolerant mineral processing circuits
    (Elsevier, 2017-07-25) Moon, EM; Ogden, MD; Griffith, CS; Wilson, A; Mata, JP
    Using X-ray absorption spectroscopy, we have identified the mechanism by which chloride impacts the extraction of U(VI) by a weak base anion exchange resin from acidic sulfate solutions. The amount of chloride present affects U(VI) speciation both in the feed solutions and adsorbed by the resin, and we find three distinct U(VI) species taken up by the resin across the salinity gradient, directly corresponding to changes in levels of U(VI) extraction. These findings are integral to the effective design of mineral processing circuits incorporating seawater—a cheaper and more sustainable water source than fresh water. © 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V.