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Purification of molybdenum trioxide calcine by selective leaching of copper with HCl–NH4Cl

Nam, Y.I., Seo, S.Y., Kang, Y-C, Kim, M.J., Senanayake, G. and Tran, T. (2011) Purification of molybdenum trioxide calcine by selective leaching of copper with HCl–NH4Cl. Hydrometallurgy, 109 (1-2). pp. 9-17.

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The leaching of Mo, Cu and Fe from MoO(3) calcines (59-61% Mo) containing 1-2% Cu, 1-2% Fe and other impurities produced from roasting molybdenite (MoS(2)) concentrate was examined using water and a series of chloride lixiviants, including NH(4)Cl (0.6 M), HCl (0.115-1.40 M) and a mixture of HCl (0.70 M) + NH(4)Cl (0.1-0.93 M) at a solid/leachant (w/v) ratio of 1:1 and within the temperature range 25-70 degrees C. Stabcal modelling showed that there are many compounds formed from Cu, Fe and Mo co-exist in the solution. Optimisation studies show that HCl solutions of concentrations >= 0.35 M are capable of dissolving >80% of Cu within 1 h. The addition of NH(4)Cl (0.30-0.93 M) to 0.7 MHCl reduces the dissolution of Mo to <0.5%, due to the formation of a precipitate containing mainly NH(3)(MoO(3))(3), as confirmed by X-ray diffraction. A mixture of 0.7 M HCl and 0.6 M NH(4)Cl at ambient temperatures removes Cu to <0.5% within 2 h, as required for the production of Fe-Mo alloys at Kwangyang Ferro Alloys Co. (Korea). Although not required, Fe was removed to <0.6% whereas most other metal impurities were removed to <0.1%. Pilot plant trials over 7 campaigns, each treating 2.0-2.2 tonnes of MoO(3) calcine containing 2.1% Cu using 1.44 M NH(4)Cl and 0.97 M HCl at an ambient temperature yielded final products containing 0.22% Cu as required. Mass balance calculations (closure to 96-99%) of the pilot plant trials confirm that the Mo loss during leaching is around 0.5%.

Item Type: Journal Article
Murdoch Affiliation(s): School of Engineering and Energy
Publisher: Elsevier BV
Copyright: 2011 Elsevier B.V. All rights reserved.
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