Denis Bykov, Delft University of Technology, Delft Reactor Institute, for explaining the radioactivity of the element promethium (Pm). Yongxiang Yang, Delft University of Technology, Department of Materials Science and Engineering, for providing me with some literature on the recycling of rare earth elements.
Introduction
The discovery of the rare earth metals began at the end of the 18th century. By the end of the 19th century, all but two rare earth metals had been discovered.
Atomic Structure
Radioactivity
Name
A sawtooth pattern can be seen in the REE sequence itself (Fig. 1.3), which is due to the Oddo-Harkins rule, which states that elements with an even atomic number have a higher abundance than elements with an odd atomic number. number (Oddo1913; Harkins1917).
Geochemical Behavior
This is due to the large ionic radius of the REE (with the exception of scandium). As a result, yttrium and the lanthanides tend to be concentrated in late magmatic fluids and late crystallizing mineral phases (McLennan 2012).
The Deposit at Ytterby
In 1947, promethium, the last of the rare earth elements, was discovered (Murphy 2006), and this closed a period of almost 150 years of painstaking, careful chemical research to isolate and identify these fascinating elements (Szabadvary 1988). In: Gschneider Jr KA, Eyring L (eds) Handbook of the Physics and Chemistry of the Rare Earths, Volume 11.
Major Ore Minerals
- Monazite
- Bastnaesite
- Xenotime
- Eudialyte
Summary This chapter provides an overview of the major and minor ore minerals in the rare earths and of the related major ore deposits. Since most of the rare earths are mined in China, the impression may arise that ore deposits of these metals occur in few other places on Earth.
Minor REE Minerals
Allanite is a disilicate (sorosilicate) mineral from the epidote group with the general formula (Ca, Ce)(Al, Fe2+)(Si2O7)(SiO4)O(OH). This appears to be mostly La2O3+ Ce2O3, although Nd2O3 is also reported from LREE in concentrations up to about 3 wt.
REE-Containing Rocks
Ore Deposits of the Rare Earths
Mountain Pass
Geological exploration in the area started as early as 1861, but the most important discovery, the rich REE deposit, was made much later. During prospecting for uranium in 1949, a highly radioactive outcrop was found in a vein, close to the shaft of the Sulphide Queen lead and gold mine.
Bayan Obo, Inner Mongolia, China
Most researchers agree that the ores themselves formed by hydrothermal alteration (Yang et al.2009; Yang and Le Bas2004;. The origin of the hydrothermal fluid is either a mantle-derived carbonatitic magma (Zhang et al.2002) or related to (carbonatitic) magma generation as a result of subduction (Drew et al found an age window of 450–555 Ma for the formation of the deposit, which is roughly Early Cambrian to Late Ordovician.
Mount Weld, South-West Australia
At Mount Weld, most of the REE and Y are incorporated into secondary monazite, cervite, and plumbogumite-group minerals.
Il í maussaq Alkaline Complex, South Greenland
The Motzfeldt Center within the Igaliko Complex can be found about 60 km northeast of the Ilímaussaq Complex. The inferred roof zone is the most extreme in diversity of rock types and enrichment of the elements mentioned above (Finch et al.2001; Tukiainen2014).
Pilanesberg, South Africa
The rock units of the Motzfeld deposit are highly variable in texture and mineralogy, and contain very high concentrations of Th, U, Nb, Ta, Zr and REE and volatile components such as F and H2O.
Steenkampskraal, South Africa
The current mine operator is Steenkampskraal Monazite Mine (Pty) Ltd. SMM), which is 75% owned by Rare Earth Extraction Company ("Rareco"). The monastic district of Steenkampskraal is located in the southern part of the Namaqua-Natal metamorphic province.
Hoidas Lake, Canada
Apatite and allanite contain most of the REE, with only small amounts of monazite and bastnaesite present. There are several hypotheses regarding the origin of the mineralizations, which have been summarized by Halpin (2010).
Thor Lake
The Hoidas Lake REE deposit is a branching and rejoining vein system in granitic tonalika intrusive rocks.
Strange Lake and Misery Lake
The average composition of the ore from Strange Lake is shown in table 2.10 (Quest Rare Minerals2014).
Nolans Bore Deposit, Australia
Norra K ä rr, Sweden
Lovozero and Khibina Massifs,
This is one of several carbonatite complexes in southern Malawi associated with the Shire Valley section of the East African Rift System. The Songwe Hill Rare Earth Element (REE) project, which will be operated by Mkango Resources Ltd., is within 100% ownership of the Phalombe License, which covers part of the Cretaceous Chilwa Alkaline Province of South Malawi (Mkango Resources Ltd2014) .
Maoniuping, Sichuan, China
Chinese Ion Adsorption Deposits
Dong Pao, Vietnam
Resources in the Deep Sea
Pelagic Muds
Crusts on Seamounts
Exploitation of Deep-Sea Deposits
Ngwenya BT (1994) Hydrothermal rare earth mineralization in Tundulu Complex carbonatites, Malawi: processes at the fluid/rock interface. Geochem: Expl Environ Anal Stoltz NB, Meyer FM (2012) Economic potential of rare earth elements in Khibina apatite.
Introduction
Abstract This chapter discusses the chemical and physical properties of the lanthanides, some of which are somewhat special. It lists the known isotopes by element and explains the radioactivity of promethium, the only rare earth element that has only radioactive isotopes and no stable isotopes.
The Lanthanide Series
Lanthanide Oxides
However, some of the lanthanides can have several valences in one and the same oxide, so formulas are given to express this phenomenon. 3The Oddo—Harkins rule states that elements with an even atomic number (such as carbon) are more common than elements with an odd atomic number (such as nitrogen).
Scandium and Yttrium
The Lanthanide Contraction
Also due to the lanthanide contraction, yttrium has an ionic radius comparable to that of the heavier REE species in the holmium-erbium region. The effect of the lanthanide contraction is noticeable up to platinum (Z5 = 78), after which it is no longer visible due to the so-called Inert Pair Effect (Encyclopedia Britannica 2015).
Radioactivity and Isotopes
- Lanthanum (Element 57)
- Cerium (Element 58)
- Praseodymium (Element 59)
- Neodymium (Element 60)
- Promethium (Element 61)
- Samarium (Element 62)
- Europium (Element 63)
- Gadolinium (Element 64)
- Terbium (Element 65)
- Dysprosium (Element 66)
- Holmium (Element 67)
- Erbium (Element 68)
- Thulium (Element 69)
- Ytterbium (Element 70)
- Lutetium (Element 71)
The half-life of most radioisotopes is even shorter than 4 minutes (Table 3.10). All other radioactive isotopes have half-lives of less than 64 hours and most have half-lives of less than 2 minutes.
Magnetism
Chemical Behavior
- Air and Oxygen
- Nitrogen
- Hydrogen
- Carbon
- Silicon
- Refractory Metals
- Acids and Bases
- Water
Rare earth mononitrides are very stable and comparable in stability to those of titanium or zirconium (Gupta and Krishnamurthy 2005). Rare earths containing thermally unstable ions such as OH-, CO32- or C2O42- are first converted to a basic derivative and finally to an oxide when heated (Gupta and Krishnamurthy 2005).
Luminescence
Finally, divalent europium exhibits luminescence in the blue part of the visible spectrum (Andres and Chauvin2012). Summary This chapter deals with rare earth mineral processing (making the mined ore into a concentrate of the valuable minerals), and rare earth extraction metallurgy (how to get the metals from the concentrate).
Introduction
Mineral Processing and Extraction of Rare Earths
Hard Rock Deposits
Regrinding will depend on the relative amounts of different types of particles and the quality of the ore. Since rare earth ores are hardly magnetic, gravity separation or flotation would be useful separation techniques.
Placer Deposits
The quality of the concentrate is expressed as the grade of the concentrate, which indicates the purity of the concentrate (Gupta and Krishnamurthy2005). In Mount Weld, Australia, the physical concentration of the REE minerals is carried out as follows: the mining material is crushed, ground and whistled to produce a concentrate with a REO content of 40%.
Chemical Treatment to Decompose the Mineral
However, washing out the rare earths from the hydroxide cake with hydrochloric acid is also very effective. The rare earths are then separated and purified through solvent extraction (Gupta and Krishnamurthy 2005).
Separation Processes
- Selective Oxidation
- Selective Reduction
- Fractional Crystallization
- Fractional Precipitation
- Ion Exchange
- Solvent Extraction
Separation of rare earths by solvent extraction is currently the most popular method for obtaining very pure fractions of each rare earth. The use of solvent extraction to separate rare earths has many advantages.
Scandium
Summary This chapter gives an overview of the most important applications of the rare earth elements. The permanent magnets themselves have a large number of different applications, which are listed in this chapter.
Introduction
Scandium
Dilute solutions of scandium sulfate, when applied to corn, peas, and wheat, increase the number of seeds that successfully germinate (Emsley 2001).
Yttrium
The radioactive isotope Sc40 is used as a tracer, for example, in refinery installations for cracking crude oil. Yttrium-iron garnet (YIG) made in large crystals can be used in optical applications and, when deposited as a thin layer, can be used for magnetic recording.
Lanthanum
- Alloy
- Batteries
- Catalyst
- Special Optical Glasses
- Superconductor
- Phosphors
Yttrium is also widely used in phosphors for lamps and appears in compounds such as YVO4: Eu and Y2O3 (Hammond 2015). Technically, it is an extension of the Ni-Cd batteries, with a hydrogen-absorbing negative electrode replacing the cadmium-based electrode.
Cerium
- Polishing Compound
- Fluid Catalytic Cracking
- Catalytic Converter
- Component in Special Glass
- Alloys
- Pigment
- Other
One of the most important alloys in which cerium is an important component is the so-called misch metal (Wikipedia 2015a) (from the German, "Mischmetall" meaning "mixed metal"). The most common use of misch metal is in the lighting devices of lighters and torches, where it is commonly called "flint".
Praeseodymium
Neodymium
A well-known method to increase coercivity in Nd–Fe–B magnets is to replace Nd with heavy rare earth elements (HREEs) such as dysprosium (Dy) and terbium (Tb) (Dhakal et al. 2014; Hirosawa et al. 1986; Hirota et al. 2006). Neodymium is also used as a dopant in yttrium-aluminum garnet (YAG) lasers or Nd:YAG lasers (Geusic et al.1964).
Promethium
Samarium
Europium
Gadolinium
Terbium
Dysprosium
Holmium
Also, holmium is used as a colorant for cubic zirconium (imitation diamond) and glass, producing yellow or red colors (Fig.5.7).
Erbium
Erbium's metallurgical uses are few, as it degrades slowly in air and is attacked by water. However, it is added to alloys with metals such as vanadium, as it lowers their hardness.
Thulium
Ytterbium
Lutetium
Wickersheim KA, Lefever RA (1964) Luminescent behavior of the rare earth metals in yttrium oxide and related compounds. Summary This chapter discusses global production of rare earths, identifies projected shortages and surpluses for certain rare earths (the “balance problem”), and explains how China is the largest producer of rare earths in the world.
Introduction
Global REE Production
However, the commercial importance of rare earth elements does not match the amount used. Now the “balance problem” is the balance between the abundance of rare earth elements in ores and the demand in economic markets (Binnemans et al. 2013).
How China Became the World ’ s Largest REE Producer
In 1987, the Open Laboratory of Rare Earth Chemistry and Physics was established at the Changchun Institute of Applied Chemistry. In 2002, the laboratory was renamed, and in 2007 it became the main State Laboratory of Rare Earth Resource Utilization (Hurst2010).
The REE-Crisis (2009 – 2013)
Massari S, Ruberti M (2013) Rare earth elements as critical raw materials: focus on international markets and future strategies. Accessed November 2014 The Sydney Morning Herald (2015) Molycorp, the only rare earth producer in the US, files for bankruptcy.
Introduction
It identifies specific sources of materials that can be used for recycling, such as permanent magnets, lamp phosphors, CRT and flat panel displays, polishing media, batteries, and bulk waste products such as red mud, a waste product from the Bayer process, and phosphogypsum, a by-product from the production of phosphoric acid. Since rare earth recycling has not yet been done on a large scale, some pros and cons of rare earth recycling are also discussed: why you would or wouldn't do it.
Sources for Recycling
- Permanent Magnets
- Lamp Phosphors
- CRT Screens and Flat-Panel Screens
- Polishing Media
- Nickel-Metal-Hydride Batteries
- Bulk-Waste Products
The concentrations of the solutes in the two phases depend on the relative affinities for the two solvents. The concentration of rare earth elements (REE) in the studied bauxite residue was about 0.1 wt. %.
Recycling, Pros and Cons
Gupta CK, Krishnamurthy N (2005) Extractive metallurgy of rare earths, CRC Press, 484 pp IPC (2015) Future supply of rare earth elements—IPC—association connecting electronic industries.http://www.ipc. org/ContentPage. aspx?pageid=future-supply-of-rare-earth-elements. Tang K, Ciftja A, van der Eijk C, Wilson S, Tranell G (2013) Recycling of rare earth oxides from spent rechargeable batteries using waste metallurgical slag.
