**3. Rare earth elements – physicochemical properties**

104 Ion Exchange Technologies

µg/g (Goering, et al. 1991).

REEs are used in fairly large quantities.

**Figure 2.** The generic scheme of REE cycle (Du & Graedel, 2011)

As for their distribution in the environment and in living organisms it should be stressed that they are found, as mentioned above, in the earth crust in a relatively wide range (Hedrick, 1993; Hedrick, 1995). Moreover, they are found in the North Atlantic Ocean waters in very low concentrations. The predominant species are carbonates, such as La2(CO3)3 with the concentration 0.002-0.005 ppb in the case of La(III), Ce(III) and Nd(III) and from 4 to 20 times less in the case of other lanthanides. The studies of the pathways of La(III), Ce(III), Th(IV) and Sm(III) from the soil to plants and farm animals show that sorption and soil abundance decrease in the following order: Ce(III) > La(III) > Th(IV) > Sm(III) (Linsalata, et al. 1986). The levels of lanthanides in healthy human tissues have been reported as follows: liver 0.005 µg/g of ash, kidney 0.002 µg/g, lung 0.004 µg/g, bones 0.2-1.0

In the paper by Du & Graedel (2011) the first quantitative life cycles (for the year 2007) for ten rare earth elements: La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III) were presented. In the charts it was shown that after extraction from ores using different separation processes the mixed rare earth element concentrates are produced. Thereafter, they are separated from each other into individual rare earth element compounds (i.e., oxides, chlorides, fluorides). The compounds are converted into pure metals or alloys and further transformed into intermediate products. Purification of metals is by electrolysis or vacuum reduction. Production of alloys is either by direct co-reduction of the rare earth element compounds or by melting and casting of metals. The intermediate products are manufactured into final goods. When the products containing rare earth elements are discarded at the end-of-life (EOL), the quantity of rare earth element material in use is lost unless recycling occurs. The idea of generic scheme for the REE cycle is presented in Fig.2. Losses of rare earth elements occur at five points in the cycles: mining, separation, fabrication, manufacturing, and waste management. The authors also emphasize that recycling of rare earth elements is challenging and it appears possible for metallurgical applications, automobile catalysts, magnets in wind turbines and automobiles, in which Lanthanides are characterized by great similarity with respect to chemical properties. This similarity is considered by approximate electron structure of exterior coating and ionic radii. Generally, the electron configuration of scandium, yttrium and lanthanum can be written as *(n-1)d1ns2*. The elements occurring after lanthanum do not develop the subcoating *5d* (except gadolinium and lutetium, which possess the electrons *5d1*) but the subcoating *4f*. Considering lanthanides as *f*-electron elements, the configuration *4f1-145d0-16s2* can be ascribed to them. According to some authors also lanthanum can be considered as *f*-electron element (Charewicz, 1990).

The electrons reaching the subcoating *4f* do not affect significantly chemical properties of the elements with the increasing atomic number. All lanthanides have the same oxidation number +3. Passing into the three positive ions, the lanthanide atom loses *6s* electrons and one *5d* electron (if it possesses) or *4f* electron (in the case *5d* electron does not occur). Cerium, praseodymium and terbium as well as neodymium and dysprosium can also have the oxidation number +4 but samarium, europium and ytterbium the oxidation state +2. Also cerium, neodymium and thulium form low stability compounds with the oxidation number +2.

Passing from scandium to yttrium the atomic radius increases from 164.1 pm to 180.1 pm. Also the radius of the ions of the above mentioned elements increases with the oxidation number +3 (from 88.5 pm to 104 pm). In the case of lanthanides the situation is different. The number of electron coatings does not change with the increasing atomic number.

The effect of electrons reaching the *4f* subcoating on the atom size is small. An important factor is the increasing atomic number as well as increased attraction of valency electrons by the nuclei with its charge increase. This leads to the decrease of atomic and ionic radii. This phenomenon is called *lanthanide contraction.* The atomic radius decreases from 187.7 pm (for La) to 173.4 pm (for Lu) in the lanthanide series. Europium whose atomic radius is 204.2 pm and ytterbium of the radius 194.0 pm are the exceptions (Cotton, 2006).

The contraction phenomenon is characteristic of lanthanide ions with different oxidation numbers and it is the most evident for the ions Ln3+. The ionic radius decreases more quickly from lanthanum to gadolinium reaching the value from 115 pm to 107.8 pm and more slowly from gadolinium to lutetium reaching the values: 106.3 pm for terbium, 105.2 pm for dysprosium, 104.1 pm for holmium, 103 pm for erbium, 102 pm for thulium, 100.8 pm for ytterbium and 100.1 pm for lutetium. In the case of gadolinium there occurs the so called *gadolinium break.* 

### **4. Rare earth occurrence and the market**

Consumption of rare earth elements in individual countries all over the world is the measure of their technological level and modernity. This is evidenced by concurrence of intensive development of production of many new materials and possession of rare earth elements separation and purification technology. This is also reflected in the total number of papers registered in Chemical Abstracts of American Chemical Society (CA) which gradually increases (Fig.3). In 2007 the total number of papers in CA was around 1 million and the percentage of papers related with rare earths was about 3%.

**Figure 3.** The number of papers related to rare earths in Chemical Abstracts of American Chemical Society (Adachi, et al. 2010).

As follows from Fig.3 there has been the high leap of increase of the number of Chinese papers and a sharp decline in the Japanese one since 2001 probably due to greater research funding and reforming of research organization systems in China such as the foundation of the State Key Laboratory of Rare Earth Materials and Application and the State Key Laboratory of Rare Earth Resource Utilization. According to Adachi et al. (2010) in 2008 in such fields of research as: separation, complexes, electrolysis, oxides, spectroscopy, RKKY interaction, Kondo effect, organometallics, magnet China, magnetism, crystal fields, superconductors, battery, hydrides, phosphors, capacitors, polishing agents, environment, recycling, catalysis and catalysts China is the leader in 16 of them (even in such sections as separation of rare earths, complexes, electrolysis, oxides and spectroscopy) and the growth is faster than in other countries (Fig.4a-d).

In recent few years China has contributed about 97% of the supply on the world market of rare earth elements, whereas according to the United States Geological Survey in 2009 the total resources were about 99 million tons of rare earth. In that China had about 37%, CIS (Commonwealth of Independence States-the former Soviet Union) had about 19% and USA about 13% (Fig.5).

This is reflected in a new supply risk index for chemical elements or element groups which are of economic value published by British Geological Survey (2011) (Table 1). The risk list highlights a group of elements where global production is concentrated in a few countries and which are at risk of supply disruption. On it rare earths (risk index 8.0, fifth position), antimony, platinum group metals, mercury, tungsten and niobium are included. The list also shows the current importance of China in production of many metals and minerals.

Society (Adachi, et al. 2010).

**0**

**2000**

**4000**

**Number of papers**

**6000**

**8000**

**10000**

about 13% (Fig.5).

is faster than in other countries (Fig.4a-d).

elements separation and purification technology. This is also reflected in the total number of papers registered in Chemical Abstracts of American Chemical Society (CA) which gradually increases (Fig.3). In 2007 the total number of papers in CA was around 1 million

> **Japan China France Germany Russia USA Others**

**Figure 3.** The number of papers related to rare earths in Chemical Abstracts of American Chemical

**1990 1994 1998 2002 2006 Year**

As follows from Fig.3 there has been the high leap of increase of the number of Chinese papers and a sharp decline in the Japanese one since 2001 probably due to greater research funding and reforming of research organization systems in China such as the foundation of the State Key Laboratory of Rare Earth Materials and Application and the State Key Laboratory of Rare Earth Resource Utilization. According to Adachi et al. (2010) in 2008 in such fields of research as: separation, complexes, electrolysis, oxides, spectroscopy, RKKY interaction, Kondo effect, organometallics, magnet China, magnetism, crystal fields, superconductors, battery, hydrides, phosphors, capacitors, polishing agents, environment, recycling, catalysis and catalysts China is the leader in 16 of them (even in such sections as separation of rare earths, complexes, electrolysis, oxides and spectroscopy) and the growth

In recent few years China has contributed about 97% of the supply on the world market of rare earth elements, whereas according to the United States Geological Survey in 2009 the total resources were about 99 million tons of rare earth. In that China had about 37%, CIS (Commonwealth of Independence States-the former Soviet Union) had about 19% and USA

This is reflected in a new supply risk index for chemical elements or element groups which are of economic value published by British Geological Survey (2011) (Table 1). The risk list highlights a group of elements where global production is concentrated in a few countries and which are at risk of supply disruption. On it rare earths (risk index 8.0, fifth position), antimony, platinum group metals, mercury, tungsten and niobium are included. The list also shows the current importance of China in production of many metals and minerals.

and the percentage of papers related with rare earths was about 3%.

Investigation of Sorption and Separation of Lanthanides on the Ion Exchangers of Various Types 107

**Figure 4.** The number of papers related to (a) separation, (b) complexes, (c) electrolysis and (d) oxides of REEs published by Japan, USA and China (Adachi, et al. 2010).

**2005 2006 2007 2008 Year**

**Figure 5.** The global reserves of REEs (2009) (US Geological Survey, USGS).

**2005 2006 2007 2008 Year**


**Table 1.** The risk index for chemical element group which are of economic value.

It should be mentioned that the rare earth elements resources were discovered by the Chinese scientists in Bayan Obo (Inner Mongolia) in 1927. The rare earth elements production started in 1957. At present, among 21 of Chinese Provinces and Autonomous Regions possessing rare earth elements resources (Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangxi, Jilin, Liaoning, Nei Mongol, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Yunnan, and Zhejiang) the most important are *Fujian, Guangdong, Jiangxi, Sichuan and Nei Mongol Autonomous Region*.

Among North American companies with combined resources of \$ 52.7 billion the following should be mentioned: *Molycorp Inc.*, *Avalon Rare Metals Ltd., Quest Rare Minerals Ltd.* and *Rare Element Resources Ltd.* 

From the mid-1960s to the 1980s, Molycorp's Mountain Pass mine was the world's dominant source of rare earth oxides. In 2002 they ceased production and in 2008 resumed it based on rare earth oxides from stockpiled concentrates derived from the rare earth ore that was previously mined at Mountain Pass. Since that they have been testing the innovative new processes on a commercial scale. Three facilities e.g. Molycorp Mountain Pass (Califorina), Molycorp Sillamae (Estonia) and Molycorp Tolleson (Arizona) produced 5,000 tons in 2011 and currently have been predicted to reach 8,000-10,000 tons in 2012. *Avalon Rare Metals Ltd.*  from Canada it is a mineral developmentcompany with a primary focus on the rare metals and minerals at (Thor Lake, Ontario) which has one of the highest concentrations of heavy rare earth oxides (HREOs) in the world with 26.1% of their 4.298 million tons of total rare earth oxides (TREO) composed of more expensive HREOs. Moreover, *Quest Rare Minerals Ltd.,* Canadian based the exploration company focused on the identification and discovery of new world class rare earth deposit opportunities. Their 'Strange Lake' project in Northern Quebec is believed to hold at least 2.1 million tons of TREOs in their important new rare earth elements mineralized zone named the B Zone, of which 39% is estimated to be HREOs. They expect to start production in mid-2015 to 2016, with the output initially expected to be 12,000 tons of REO/yr. On the other hand, *Rare Element Resources Ltd.* the core project 'Bear Lodge' is believed to be one of the richest LREO deposits in the USA. And with the company expecting to begin production in 2015, with an anticipated output of 11,400 tons of REO/yr, it could be well-positioned to meet growth in demand for LREOs.

The advanced stage projects of rare earth elements production in 2012 and 2013 are also proposed by Lynas Corporation Ltd. (Mt. Weld, West Australia) based on the richest known deposit of rare earth elements in the world, and a state-of-the-art Rare Earths processing plant, the Lynas Advanced Materials Plant (LAMP), currently under construction near Kuantan (Pahang, Malaysia). At the spearhead there are also Silmet (Estonian Republic) which is one of the biggest rare metal and rare earth metal producers in Europe.

In Poland rare earth elements resources do not occur (Charewicz 1990; Paulo, 1993; Paulo 1999). Since 1987 the apatite concentrates from the deposits of Chibiński Massif on Kola Peninsula have been imported to Poland as phosphorous raw material. Apatite deposits contain about 1% of REO. Therefore, the secondary resources of rare earth elements are in the form of phosphogypsum dump in the area of the former Chemical Plant 'Wizów' near Bolesławiec. In 1948 the firm was set up as a producer of sulphric acid. In 1969 -1979 it started to produce phosphoric acid and then phosphoric salts. Up to the 80s the plant was only producer of tripolyphosphate. In its area there is localized a dump of phosphogypsum including mainly calcium sulphate(VI) originating from the extraction of phosphoric acid (obtained from the apatite raw material) and on the average 0.5% of rare earth element oxides. At present over 5 million tons of the waste are found in the dump.

108 Ion Exchange Technologies

*Rare Element Resources Ltd.* 

Europe.

It should be mentioned that the rare earth elements resources were discovered by the Chinese scientists in Bayan Obo (Inner Mongolia) in 1927. The rare earth elements production started in 1957. At present, among 21 of Chinese Provinces and Autonomous Regions possessing rare earth elements resources (Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangxi, Jilin, Liaoning, Nei Mongol, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Yunnan, and Zhejiang) the most important

Among North American companies with combined resources of \$ 52.7 billion the following should be mentioned: *Molycorp Inc.*, *Avalon Rare Metals Ltd., Quest Rare Minerals Ltd.* and

From the mid-1960s to the 1980s, Molycorp's Mountain Pass mine was the world's dominant source of rare earth oxides. In 2002 they ceased production and in 2008 resumed it based on rare earth oxides from stockpiled concentrates derived from the rare earth ore that was previously mined at Mountain Pass. Since that they have been testing the innovative new processes on a commercial scale. Three facilities e.g. Molycorp Mountain Pass (Califorina), Molycorp Sillamae (Estonia) and Molycorp Tolleson (Arizona) produced 5,000 tons in 2011 and currently have been predicted to reach 8,000-10,000 tons in 2012. *Avalon Rare Metals Ltd.*  from Canada it is a mineral developmentcompany with a primary focus on the rare metals and minerals at (Thor Lake, Ontario) which has one of the highest concentrations of heavy rare earth oxides (HREOs) in the world with 26.1% of their 4.298 million tons of total rare earth oxides (TREO) composed of more expensive HREOs. Moreover, *Quest Rare Minerals Ltd.,* Canadian based the exploration company focused on the identification and discovery of new world class rare earth deposit opportunities. Their 'Strange Lake' project in Northern Quebec is believed to hold at least 2.1 million tons of TREOs in their important new rare earth elements mineralized zone named the B Zone, of which 39% is estimated to be HREOs. They expect to start production in mid-2015 to 2016, with the output initially expected to be 12,000 tons of REO/yr. On the other hand, *Rare Element Resources Ltd.* the core project 'Bear Lodge' is believed to be one of the richest LREO deposits in the USA. And with the company expecting to begin production in 2015, with an anticipated output of 11,400 tons of

are *Fujian, Guangdong, Jiangxi, Sichuan and Nei Mongol Autonomous Region*.

REO/yr, it could be well-positioned to meet growth in demand for LREOs.

The advanced stage projects of rare earth elements production in 2012 and 2013 are also proposed by Lynas Corporation Ltd. (Mt. Weld, West Australia) based on the richest known deposit of rare earth elements in the world, and a state-of-the-art Rare Earths processing plant, the Lynas Advanced Materials Plant (LAMP), currently under construction near Kuantan (Pahang, Malaysia). At the spearhead there are also Silmet (Estonian Republic) which is one of the biggest rare metal and rare earth metal producers in

In Poland rare earth elements resources do not occur (Charewicz 1990; Paulo, 1993; Paulo 1999). Since 1987 the apatite concentrates from the deposits of Chibiński Massif on Kola Peninsula have been imported to Poland as phosphorous raw material. Apatite deposits contain about 1% of REO. Therefore, the secondary resources of rare earth elements are in Despite the fact the Chinese resources are estimated to be 37% (Fig.5), due to intensive promotion of their exploitation and large expenditure of money on investigations, at present China is a monopolist imposing the prices of these elements. The latest policy of China – decrease of export by 40% and temporary ban of export to Japan is reflected in an immediate rise in raw materials prices (Fig.6).

**Figure 6.** REO prices from 2007 to 2010 (Congressional Research Service report).

High prices mostly affected HREO. The price of terbium oxide used in production of hybrid cars or solar systems increased from \$600 in the end of 2010 to \$ 3200 for a kilogram at the beginning of 2011. As follows from the data of the firm Shanghai Metals Market, despite over 20% decrease in the prices in the end of 2011, temporary stoppage of production by the largest Chinese firms (among others, Inner Mongolia Baotou Steel Rare-Earth, Hi-Tech Co.) is to stabilize the market and prevent from further drop in prices. According to the China authorities the high cost of mining is connected with huge environmental cost of rare earth processing. On one hand, the mining of rare earths causes the erosion of land and water, on the other, the emission after the mining further damages the environment. Additionally, the China government will not approve of any new rare earth separation projects before 2015. To protect rare earth resources, rare earth producers will be required to have a minimum mine output capacity of 300,000 tons/yr of ore for light rare earths and 3,000 tons/yr (REO) for ion adsorption rare earths. The Chinese government will ban monazite mining if the monazite contains radioactive elements. For rare-earth separation, producers will be required to have a separation output capacity of 8,000 tons/yr (REO) of mixed rare earths, 5,000 tons/yr (REO) of bastnaesite, and 3,000 tons/yr (REO) of ion-adsorption rare earths.

Metal smelting producers must have an output capacity of 1,500 tons/yr. Rare earth producers will be required to meet the environmental emission standards; otherwise, they will be shut down (China Ministry of Environmental Protection, 2011; Tse, 2011). Therefore, the countries, which are potential miners of rare earth elements start to search for their deposits and exploitation. For example, based on the released data from USGS (2010) there is an interesting situation concerning rare earth elements sources from Brazil.
