Abstract
Eudialyte ores from Norra Kärr (Sweden) and Kringlerne (Greenland) are considered a potential source of rare-earth elements (REE) for the development of a sustainable REE industry outside China. Magnetic separation is successfully applicated to recover eudialyte as a magnetic fraction. In the case of the Norra Kärr deposit, up to 20% of the REE and up to 40% of the Zr are lost during mineral processing in the non-magnetic fraction. Zr and REE are associated with non-magnetic minerals such as catapleiite, low- or non-magnetic eudialyte species, and both their intergrowths. Besides zirconosilicates such as catapleiite and eudialyte, the non-magnetic fraction has valuable and already-liberated minerals such as alkali feldspars and nepheline, which should not be considered as tailings. In this investigation, a possible way to recover REE bearing zirconosilicates from the non-magnetic fraction using flotation is presented. First, a low-grade eudialyte concentrate (1.8% Zr, 0.94% REE) from ground ore was obtained using magnetic separation. The non-magnetic fraction was then treated using froth flotation, and a Zr-REE bearing product (9% Zr, 1.5% REE) was obtained as froth product. For this purpose, phosphoric acid esters were used as selective collectors for zirconosilicates at a pH between 3.5 and 4.5. The reagent regime could be proposed not only to recover Zr- and REE-bearing minerals, but also simultaneously to remove Fe, Ti, and other colored impurities from the nepheline-feldspar product and to minimize the tailings volume.
Highlights
The development of a modern green and low-carbon industry in developed countries requires a sustainable and fair supply chain of critical raw materials such as cobalt, lithium, vanadium, and rare earth elements (REE) [1,2,3]
For this study, the main aim of the magnetic separation was the preparation of feed materials, which contain lost non-recoverable Zr- and REE-bearing minerals
It was aimed to recover complex rare zirconium minerals such as non-magnetic eudialyte species and catapleiite using froth flotation. These minerals normally get lost during wet, high-magnetic separation stages into the non-magnetic fraction
Summary
The development of a modern green and low-carbon industry in developed countries requires a sustainable and fair supply chain of critical raw materials such as cobalt, lithium, vanadium, and rare earth elements (REE) [1,2,3]. Norra Kärr is a peralkaline nepheline-syenite intrusive complex located in southcentral Sweden and is defined as comprising agpaitic rocks [6] It is a unique deposit of REE and HFSE elements with a high ratio of HREE relative to total REE (TREE) represented by eudialyte group minerals (EGM). The main aim of this research work is to determine a reagent regime to recover Zr- and REE-bearing minerals from the Norra Kärr ore by flotation, which in this case are currently lost into the non-magnetic fraction. With the use of froth flotation, it would be possible to simultaneously remove undesirable colored impurities and their intergrowths such as iron- and titanium-bearing minerals (titanite, micas (muscovite), pyroxenes, aegirine) from the non-magnetic fraction In this case, the tailings product of the froth flotation must be considered as an additional marketable by-product such as nepheline syenite. The identified gangue minerals are feldspars (albite Na(AlSi3O8), Minerals 2022, 12, 19 microcline K(AlSi3O8), plagioclase (Na,Ca)[(Si,Al)AlSi2]O8, pyroxenes (aegirine-augite series (Na,Ca,Fe2+,Mg)(Fe3+,Al,Fe2+,Mg,)Si2O6) and nepheline Na3K(Al4Si4O16) with its alteration and replacement products (analcime Na(AlSi2O6)·H2O, natrolite Na2Al2Si3O10·2H2O, cancrinite Na6Ca2[(CO3)2|Al6Si6O24]·2H2O)
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