Rare earth elements (REEs) refer to a group of 17 elements on the periodic table that have very similar electronic structures as well as physical and chemical properties. These 17 elements include 15 lanthanide series elements along with scandium and yttrium.
Scandium and yttrium are included because they depict very similar chemical and physical properties along with affinities with lanthanides. They are usually found in the same ore body as lanthanides.
Although REEs are plentiful in the earth's crust, they are termed rare earth elements because of the difficult nature of their extraction and purification process. Additionally, their low concentrations make their economically exploitable ore deposits very rare.
REEs are mined similar to other ores, such as steps involving mining rocks, separating ores from tailings (waste rock) and refining ores to extract the metal.
Though an additional step of separating REEs from each other is required, which is a cost-intensive, time-consuming, and difficult process.
REEs are essential to many high-tech industrial as well as devices and applications that we use in our daily lives. Electronics, clean energy, aerospace, automotive, and defence are among the key industrial application areas for REEs.
Luminescent and catalytic properties of REEs make them highly suitable for green products and high technology applications.
As per data from the US Geological Survey, China is the world's largest producer of REEs. China accounted for almost 58% of the global production in 2020.
Some of the other key producers of REEs are the United States, Myanmar, Australia and Madagascar, accounting for ~39% of the worldwide output.
· Magnetic properties: REEs like neodymium (Nd), dysprosium (Dy), and samarium (Sm) are used in producing magnets for electric motors and turbines, aircraft and missile guidance systems, computer hard drives, etc.
They have large capacities for storing a large amount of magnetic energy compared to other magnetic elements. They are naturally magnetic; however, they lose their magnetic nature even at room temperature.
To overcome this issue, transition metals, such as iron or cobalt, are added to produce REEs alloys, thus retaining their magnetism at higher temperatures and increasing their magnetic strength.
· Luminescent properties: Some REEs like europium (Eu), yttrium (Y), erbium (Er), and neodymium (Nd) produce light when stimulated by electromagnetic radiation.
This property of REEs makes them highly sought-after for the manufacturing of LEDs and compact fluorescent light bulbs. Erbium-doped fibre amplifiers are used in high-capacity fibre-optic lines deployed for internet data transfer and long-distance telephone calls worldwide.
· Electrical properties: A mix of cerium (Ce), lanthanum (La), neodymium (Nd), and praseodymium (Pr) is termed mischmetal and is used to make the anode of nickel–metal hydride (NiMH) batteries used in hybrid cars and portable construction tools.
This mischmetal is cheaper than a normal anode as individual metals are not required to be separated from each other. It also enhances the battery's life span and keeps a higher energy density.
· Catalytic properties: Because of their electron structure and comparative abundance, cerium and lanthanum are commonly used as catalysts (accelerators) in many chemical reactions and processes.
For example, gasoline-powered cars use cerium in their catalytic converters. Lanthanum is used for crude oil refining by assisting fluid catalytic cracking in extracting useful hydrocarbons from crude oil.
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Frequently Asked Questions
Normally adjacent elements in the periodic table have very different chemical properties. The reason for this is the difference in the arrangement of electrons in the outermost shells (the shell is termed the valence shell while these electrons are termed valence electrons) is different even for the adjacent periodic table’s elements.
However, in case of REEs, the arrangement of valence electrons is very similar to each other and hence they have almost identical chemical and physical properties. It is responsible for their similar reactivity; therefore, one rare earth element ore holds many rare earth elements.
Doping intentionally adds a small quantity of a certain chemical (termed an impurity) to change the property of the doped sample. It is done to enhance the intrinsic property of the base sample.
For example, high-capacity fibre-optic lines use Erbium-doped fibre amplifiers, which intensify the signal and make these optic lines suitable for internet data transfer and long-distance telephone calls worldwide.
As per Geoscience Australia, Australia accounted for 8% of the global rare earth production in 2020.
The Australian government has already included rare earths in the critical metals group. The government has introduced various programs to offer grants and funding support, in addition to significant infrastructure and resource support to related space players.
South Australia, which has significant deposits of rare earths in ionic clay, has become one of the key centres of rare earth mineral exploration.
Lynas Rare Earths (ASX:LYC), one of the world’s largest producers of REEs, has two major operations. The Lynas Mt Weld mine in Western Australia is among the world's most premium rare earths deposits. The company’s processing plant in Malaysia, also, the world’s largest single REEs processing plant, delivers high-quality separated REE materials to Asia, Europe, and the United States.
The mining of REEs is similar to the mining of other metals. However, an additional process of solvent extraction is required due to their affinity. This process is difficult and cost intensive.
This process requires dissolving different concentrations of REEs into two immiscible liquids. After this, several acids, having affinities for different REEs are mixed, and then the produced mixtures are allowed to settle.
With each separation, the concentration of a specific metal increases. This process, when repeated over hundreds or thousands of cycles, can deliver a desirable purity of over 99.9%.