RARE EARTH MINERALS/ELEMENTS

Rare earth minerals or elements are invaluable because of their unusual chemical and physical properties. The rare earth elements (REEs) distinctive properties are due to their atomic structure, especially the configuration of their electrons which is unlike that of other elements.

Rare earth elements (REEs) are a group of 17 metallic elements consisting of the 15 lanthanides (La-Lu on the periodic table) plus scandium (Sc) and Yttrium (Y). The fifteen lanthanides with atomic numbers 57 (lanthanum, La) to 71 (lutetium, Lu), together with yttrium (Y, atomic number 39) and scandium (Sc, atomic number 21), all have similar chemical properties. The lower atomic weight elements lanthanum to samarium (Sm), with atomic numbers 57 to 62 are referred to as the light rare earth elements (LREE), while europium (Eu) to lutetium with atomic numbers 63 to 71 are heavy rare earth elements (HREE). However yttrium, although has a lower atomic weight is grouped with the HREE because of its chemical similarity. Scandium properties are different enough from those of other REE.

The light rare earth (LREE) minerals or elements and their atomic numbers are as follows; Lanthanum (La,57), cerium (Ce,58), praseodymium (Pr,59),neodymium (Nu,60), promethium (Pm,61), samarium (Sm,62) and europium (Eu,63).

The heavy rare earth minerals or elements (HREE) and their atomic numbers are ; Gadolinium (Gd,64), Terbium (Tb,65), Dysprosium (Dy,66), Holmium (Ho,67), Erbium (Er,68), Thulium (Tm,69), Ytterbium (Yb,70), Lutetium (Lu,71), Scandium (Sc,21) and Yttrium (Y,39).

The advantages of rare earth minerals or elements are; they have unmatched magnetic properties, thereby enabling compact and powerful magnets. They enable fiber-optics lasers, camera lenses and night vision systems with no equivalent alternatives. They possess catalytic efficiency especially cerium and lanthanum which improves dramatically fuel combustion and reduce vehicle emissions. Medically gadolinium MRI contrast agents and yttrium cancer therapies have no viable substitutes. They enable miniaturization of many devices such as speakers, headphones, hard drives etc. because of their unique properties. They are very durable and can retain their magnetic properties in extreme heat, cold and radiation.

The disadvantages of rare earth minerals are; they pose a threat to the environment due to the toxic and radioactive waste (thorium, uranium occurs naturally with REEs) associated with mining and processing. They have low potential to be recycled and have high processing cost since they require complex solvent extraction with hundreds of steps. Their radioactive by products poses great environmental concern and can cause severe water and soil contamination.

They find widespread application as magnetic products in wind turbine generators, electric and hybrid vehicle motors, hydrogen fuel cells, consumer electronics such as smartphones speakers, vibration motors, hard disk drives and display phosphors for LED/LCD screens. They are used medically as MRI contrast agents, cancer radio therapy and surgical lasers. They also find vast application in defense and aerospace industries as guided missile actuators, radar and sonar systems, jet engine alloys and night vision goggles. Industrially they are useful in petroleum refining catalyst, glass polishing and UV filtering as well as steel and aluminum strengthening. They are also used as nuclear reactor control rods. They are energy efficient and are used to make energy efficient fluorescent and LED bulbs, fiber optic amplifiers etc.

The future of rare earth minerals or elements depends on the advances and development of the following technologies; magnet free motor designs, recycling technology to extract rare earth elements (REEs) from e-waste thereby reduce environmental pollution. Moreover growing demand for electric vehicles and green technology will drive the future of rare earth minerals research and development.

 

SOURCES:

• The rare earth elements: An introduction by Jack H.L Vondeen.
• Rare earths science, technology, production and use by Jacques Lucas, Pierre Lucas, Thierry Le Mercier, Alain Rollat and William G. Davenport.
• Rare earth elements and their minerals edited by Michael Aide and Takahitto Nakajima.
• The science of rare earth elements: Concepts and applications by Frank R. Spellman.
• The rare earth elements edited by David A. Atwood.