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Fundamentals of Rare Earth Mineral Flotation—
Understanding Silicates to Increase Metallurgical Performance
Abdul Wasiu Mamudu, Vimeipha Vilayphone, Trenin Bayless, Courtney Young
Metallurgical &Mineral Processing Engineering, Montana Technological University
ABSTRACT: Flotation is commonly used to process rare earth minerals (REMs). However, the metallurgical
performance of REM flotation is inconsistent because the REMs are solid solutions possessing rare earth
elements (REEs) that vary in type and concentration. Researchers at Montana Tech have investigated pure
synthetic REMs and shown that the flotation of rare earth oxides (REOs), carbonates (RECs) and phosphates
(REPs) depends on the REE cation size as well as the associated anion. These phenomena are attributed to
coordination number (CN) as well as lanthanide contraction (LC). New research shows this phenomenon also
applies to silicates but greatly depends on the silicate type. Results explain the reasons for poor metallurgical
performance which can be overcome through the use of collector blends.
INTRODUCTION
Rare Earth Minerals (REMs)
Rare earth elements (REEs), despite their name, are quite
abundant in the earth’s crust. The phrase “rare earth” was
first used in 1788 to describe a peculiar black rock found
in Ytterby, Sweden. Although these elements are not scarce,
they are commonly present in low quantities and frequently
intermixed, posing challenges in their extraction and purifi-
cation. (Anon 2024 Gschneidner et al., 2023). REEs con-
sist of a group of 17 metallic elements, which encompass
scandium, yttrium, and the 15 lanthanides. They exhibit
distinctive fluorescent, conductive, and magnetic charac-
teristics, rendering them highly beneficial for a wide range
of applications, such as advanced technological equipment,
renewable energy systems, and manufacturing processes.
China has held the title of the world’s top producer of
REEs, even though these elements can be found in viable
concentrations elsewhere.
The production and extraction of rare earth minerals
(REMs) can result in the generation of substantial quantities
of other elements including rare metals such as niobium,
tantalum, cobalt, indium, zirconium, gallium, and lithium
which also play roles in many energy and technology appli-
cations. The sustainable supply of these critical elements,
including REEs, has issues due to their concentration in a
limited number of nations, despite their widespread avail-
ability (Williams 2018 Anderson 2015 Tse 2011).
REEs are commonly classified into three categories
based on their physical and chemical properties: light
(LREEs), middle (MREEs), and heavy (HREEs). LREEs
typically consists of Scandium (Sc), Lanthanum (La),
Cerium (Ce), Praseodymium (Pr), and Neodymium
(Nd). MREEs include Samarium (Sm), Europium (Eu),
Gadolinium (Gd), Terbium (Tb), and Dysprosium (Dy).
HREEs comprise Holmium (Ho), Erbium (Er), Thulium
(Tm), Ytterbium (Yb), Lutetium (Lu), and Yttrium (Y).
Pm is virtually non-existent due to the radioactive nature
of its isotopes which have half-lives too short to accumu-
late significantly in nature. In general, REE properties are
so similar that the possess few distinctions which creates
Fundamentals of Rare Earth Mineral Flotation—
Understanding Silicates to Increase Metallurgical Performance
Abdul Wasiu Mamudu, Vimeipha Vilayphone, Trenin Bayless, Courtney Young
Metallurgical &Mineral Processing Engineering, Montana Technological University
ABSTRACT: Flotation is commonly used to process rare earth minerals (REMs). However, the metallurgical
performance of REM flotation is inconsistent because the REMs are solid solutions possessing rare earth
elements (REEs) that vary in type and concentration. Researchers at Montana Tech have investigated pure
synthetic REMs and shown that the flotation of rare earth oxides (REOs), carbonates (RECs) and phosphates
(REPs) depends on the REE cation size as well as the associated anion. These phenomena are attributed to
coordination number (CN) as well as lanthanide contraction (LC). New research shows this phenomenon also
applies to silicates but greatly depends on the silicate type. Results explain the reasons for poor metallurgical
performance which can be overcome through the use of collector blends.
INTRODUCTION
Rare Earth Minerals (REMs)
Rare earth elements (REEs), despite their name, are quite
abundant in the earth’s crust. The phrase “rare earth” was
first used in 1788 to describe a peculiar black rock found
in Ytterby, Sweden. Although these elements are not scarce,
they are commonly present in low quantities and frequently
intermixed, posing challenges in their extraction and purifi-
cation. (Anon 2024 Gschneidner et al., 2023). REEs con-
sist of a group of 17 metallic elements, which encompass
scandium, yttrium, and the 15 lanthanides. They exhibit
distinctive fluorescent, conductive, and magnetic charac-
teristics, rendering them highly beneficial for a wide range
of applications, such as advanced technological equipment,
renewable energy systems, and manufacturing processes.
China has held the title of the world’s top producer of
REEs, even though these elements can be found in viable
concentrations elsewhere.
The production and extraction of rare earth minerals
(REMs) can result in the generation of substantial quantities
of other elements including rare metals such as niobium,
tantalum, cobalt, indium, zirconium, gallium, and lithium
which also play roles in many energy and technology appli-
cations. The sustainable supply of these critical elements,
including REEs, has issues due to their concentration in a
limited number of nations, despite their widespread avail-
ability (Williams 2018 Anderson 2015 Tse 2011).
REEs are commonly classified into three categories
based on their physical and chemical properties: light
(LREEs), middle (MREEs), and heavy (HREEs). LREEs
typically consists of Scandium (Sc), Lanthanum (La),
Cerium (Ce), Praseodymium (Pr), and Neodymium
(Nd). MREEs include Samarium (Sm), Europium (Eu),
Gadolinium (Gd), Terbium (Tb), and Dysprosium (Dy).
HREEs comprise Holmium (Ho), Erbium (Er), Thulium
(Tm), Ytterbium (Yb), Lutetium (Lu), and Yttrium (Y).
Pm is virtually non-existent due to the radioactive nature
of its isotopes which have half-lives too short to accumu-
late significantly in nature. In general, REE properties are
so similar that the possess few distinctions which creates