FLOATABILITY OF SYNTHETIC LIGHT AND HEAVY RARE EARTH ELEMENT
CARBONATES AND SELECTIVITY TOWARDS CALCITE
Martin Rudolph, Robert Kratzsch
Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz-Institute Freiberg for Resource Technology,
Halsbrücker Straße 34, 09599 Freiberg, Germany, phone: +49 351 260 4410, mail: m.rudolph@hzdr.de
ABSTRACT
The fourteen lanthanoid elements, also commonly referred to as rare earth elements (REE) or rare earth
metals (REM) and often including lanthanum as well as both Yttrium and Scandium, can be referred to as
the vitamins of the periodic systems table. They are used for green and high tech applications such as
powerful magnets, batteries, glasses and triband dyes. Commonly they can be found and mined as
carbonate minerals, e.g. bastnäsite, synchisite and ankylite or as phosphate minerals, e.g. monazite and
xenotim. Usually they all occur as mixed REM carbonates with different proportions of light and heavy
rare earth elements. The light rare earth elements LREE (lanthanum through samarium) are less scarce and
thus economically becoming less critical (EU list of critical elements from 2014). The heavy rare earths
HREE (europium through lutetium plus yttrium) are indeed rare, scarce and thus considered critical
elements. The ratio of LREE and HREE depends very much on the deposits. When beneficiating rare earth
carbonate minerals flotation is often an important unit process operation especially to reduce content of
silicates, calcite and barite. As flotation reagents in principle simple carboxylic acid type collectors are
used in combination with silicate and calcite depressants. It has been reported (Nature (2013), 12, 315) that
the surface wettability of REE oxides very much is influenced by high ionic radius of the REE cations. The
ionic radius is indeed one of the distinguishable properties of the REE amongst one another. Therefore the
question is how different synthetic unmixed individual LREE and HREE carbonates behave in terms of
floatability.
Results are presented for the REE carbonates of yttrium, lanthanum, cer, neodymium, dysprosium and
ytterbium with sodium oleate at different pH values. Lignin sulfonate is investigated as the selective
depressant for calcite and barium carbonate and not the REE carbonates.
KEYWORDS
Light Rare Earth Elements, Heavy Rare Earth Elements, Microflotation, Lignin Sulfonate