Abstract

BISAKA, K.; THOBADI, I.C.  and  PAWLIK, C.. Extraction of rare earths from iron-rich rare earth deposits. J. S. Afr. Inst. Min. Metall. [online]. 2017, vol.117, n.8, pp.731-739. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/2017/v117n8a2.

Rare earth metals are classified as critical metals by the United Nations, as they have found wide application in the fabrication of magnets, particularly those used in green energy technologies which mitigate global warming. Processing of ores containing rare earth elements is complex, and differs according to the nature of each ore. In the conventional process, run of mine (ROM) ores are processed in a physical separation plant to produce a concentrate from which rare earth elements are extracted via a hydrometallurgical route. To extract rare earth elements economically, multiple sequential physical and chemical separation steps are used to produce a mixture of rare earth salts, followed by purification and production of metals and alloys. Large iron-rich rare-earth-bearing deposits exist in China, Southern Africa, Canada, and Australia. Although these deposits carry significant reserves of rare earth elements, a number of them are not exploited as no economically viable process exists to do so. The mineralogy of the difficult deposits is complex, with rare earth minerals of particle size less than 20 μm disseminated in a matrix of iron oxide such as haematite, magnetite, or goethite. A process comprising fine milling for liberation of rare earth minerals, and physical upgrading of the resulting materials, would be technically challenging, inefficient, and not economically viable. Globally, research efforts are directed towards the development of novel methods and new reagents to overcome these difficulties. PyEarth^TMis a novel process currently under development at Mintek, that is aimed at achieving efficient extraction of rare earths from the mineralogically complex iron-rich, rare-earth-bearing ores. The process incorporates a preliminary smelting step to reduce the iron to the metallic state and concentrate the rare earths into the slag phase, followed by leaching of the slag and recovery of the rare earths from the leach liquor. Tests at the laboratory scale on samples from deposits originating from Southern Africa have proved that the extraction of rare earths from iron-rich, rare-earth-bearing ores using this process is technically feasible, robust, and viable.

Keywords : PyEarth^TM; iron-rich rare-earth-bearing ore; direct smelting; rare-earth-rich slag; hydrochloric leaching; rare earth.

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