Lithium was used to decrease the melting temperature of glass and to improve the melting behavior of aluminium chloride when using the Hall-Hйroult process.[31][31] These two uses dominated the market until the middle of the 1990's. After the end of the nuclear arms race the demand for lithium decreased and the sale of Department of Energy stockpiles on the open market further reduced prices.[30] Then, in the mid 1990's several companies started to extract lithium from brine; this method proved to be less expensive than underground or even open pit mining. Most of the mines closed or shifted their focus to other materials as only the ore from zoned pegmatites could be mined for a competitive price. For example, the US mines near Kings Mountain, North Carolina closed before the turn of the century. The use in lithium ion batteries increased the demand for lithium and became the dominant use in 2007.[30] New companies have expanded brine extraction efforts to meet the rising demand.[32]
4. Occurrence
According to theory, the stable isotopes 6Li and 7Li were created in the Big Bang, but the amounts are unclear. Lithium is a fusion fuel in main sequence stars. Because of the method by which elements are built up by fusion in stars, there is a general trend in the cosmos that the lighter elements are more common. However, lithium (element number 3) is tied with krypton as the 32nd/33rd most abundant element in the cosmos (see Cosmochemical Periodic Table of the Elements in the Solar System), being less common than any element between carbon (element 6) and scandium (element 21). It is not until atomic number 36 (krypton) and beyond that chemical elements are found to be universally less common in the cosmos than lithium. The reasons have to do with the failure of any good mechanisms to synthesize lithium in the fusion reactions between nuclides in supernovae. Due to the absence of any quasi-stable nuclide with five nucleons, nuclei of lithium-5 produced from helium and a proton has no time to fuse with a second proton or neutron to form a six nucleon isotope which might decay to lithium-6, even under extreme conditions of bombardment. Also, the product of helium-helium fusion (berylium-8) is immediately unstable toward disintegration to helium again, and is thus not available for formation of lithium. Some lithium-7 is formed in the pp III branch of the proton-proton chain in main sequence and red giant stars, but it is normally consumed by lithium burning as fast as it is formed. This leaves new formation of the stable isotopes lithium 6 and 7 to rare cosmic ray spallation on carbon or other elements in cosmic dust. Meanwhile, existing Li-6 and Li-7 is destroyed in many nuclear reactions in supernovae and by lithium burning in main sequence stars, resulting in net removal of lithium from the cosmos. In turn the destruction of lithium isotopes is due to their very low energy of binding per nucleon with regard to all other nuclides save deuterium (also destroyed in stars) and helium-3.[5] This low energy of binding encourages breakup of lithium in favor of more tightly-bound nuclides under thermonuclear reaction conditions.
Lithium is widely distributed on Earth but does not naturally occur in elemental form due to its high reactivity.[8] Estimates for crustal content range from 20 to 70 ppm by weight.[12] In keeping with its name, lithium forms a minor part of igneous rocks, with the largest concentrations in granites. Granitic pegmatites also provide the greatest abundance of lithium-containing minerals, with spodumene and petalite being the most commercially viable sources.[12] A newer source for lithium is hectorite clay, the only active development of which is through the Western Lithium Corporation in the United States.[34]
According to the Handbook of Lithium and Natural Calcium, "Lithium is a comparatively rare element, although it is found in many rocks and some brines, but always in very low concentrations. There are a fairly large number of both lithium mineral and brine deposits but only comparatively a few of them are of actual or potential commercial value. Many are very small, others are too low in grade."[35] At 20 mg lithium per kg of Earth's crust [36], lithium is the 25th most abundant element. Nickel and lead have the about the same abundance.
The largest reserve base of lithium is in the Salar de Uyuni area of Bolivia, which has 5.4 million tons. According to the US Geological Survey, the production and reserves of lithium in metric tons are as follows[37]:
Contrary to the USGS data in the table, other estimates put Chile's reserve base at 7,520,000 metric tons of lithium, and Argentina's at 6,000,000 metric tons.[38] Seawater contains an estimated 230 billion tons of lithium, though at a low concentration of 0.1 to 0.2 ppm.
Figure. 2. Lithium is about as common as chlorine in the Earth's upper continental crust, on a per-atom basis.
5. Production
Since the end of World War II lithium metal production has greatly increased. The metal is separated from other elements in igneous minerals such as those above. Lithium salts are extracted from the water of mineral springs, brine pools and brine deposits.
The metal is produced electrolytically from a mixture of fused lithium and potassium chloride. In 1998 it was about US$ 43 per pound ($95 per kg).[40]
Deposits of lithium are found in South America throughout the Andes mountain chain. Chile is the leading lithium metal producer, followed by Argentina. Both countries recover the lithium from brine pools. In the United States lithium is recovered from brine pools in Nevada.[41] Nearly half the world's known reserves are located in Bolivia, a nation sitting along the central eastern slope of the Andes. In 2009 Bolivia is negotiating with Japanese, French, and even Korean firms to begin extraction.[42] According to the US Geological Survey, Bolivia's Uyuni Desert has 5.4 million tons of lithium, which can be used to make batteries for hybrid and electric vehicles.[42][43]
China may emerge as a significant producer of brine-source lithium carbonate around 2010. There is potential production of up to 55,000 tons per year if projects in Qinghai province and Tibet proceed.[44]
The total amount of lithium recoverable from global reserves has been estimated at 35 million tonnes, which includes 15 million tons of the known global lithium reserve base.[45]
In 1976 a National Research Council Panel estimated lithium resources at 10.6 million tons for the Western World.[46] With the inclusion of Russian and Chinese resources as well as new discoveries in Australia, Serbia, Argentina and the United States, the total had nearly tripled by 2008.[47][48]
Figure. 3. Lithium mine, Salar del Hombre Muerto, Argentina. The brine in this salar is rich in lithium, and the mine concentrates the brine by pumping it into solar evaporation ponds. 2009 image from NASA's EO-1 satellite.
Figure. 4. Salar de Uyuni, Bolivia.
6. Applications
Because of its specific heat capacity, the highest of all solids, lithium is often used in heat transfer applications.
In the latter years of the 20th century lithium became important as an anode material. Used in lithium-ion batteries because of its high electrochemical potential, a typical cell can generate approximately 3 volts, compared with 1.5 volts for lead/acid or zinc cells. Because of its low atomic mass, it also has a high charge- and power-to-weight ratio.
Lithium is also used in the pharmaceutical and fine-chemical industry in the manufacture of organolithium reagents, which are used both as strong bases and as reagents for the formation of carbon carbon bonds. Organolithiums are also used in polymer synthesis as catalysts/initiators[49] in anionic polymerisation of unfunctionalised olefins.[50][51][52]
6.1 Medical use
Lithium salts were used during the 19th century to treat gout. Lithium salts such as lithium carbonate (Li2CO3), lithium citrate, and lithium orotate are mood stabilizers. They are used in the treatment of bipolar disorder since, unlike most other mood altering drugs, they counteract both mania and depression. Lithium can also be used to augment antidepressants. Because of Lithium's nephrogenic diabetes insipidus effects, it can be used to help treat the syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH). It was also sometimes prescribed as a preventive treatment for migraine disease and cluster headaches.[53]
The active principle in these salts is the lithium ion Li+. Although this ion has a smaller diameter than either Na+ or K+, in a watery environment like the cytoplasmic fluid, Li+ binds to the hydrogen atoms of water, making it effectively larger than either Na+ or K+ ions. How Li+ works in the central nervous system is still a matter of debate. Li+ elevates brain levels of tryptophan, 5-HT (serotonin), and 5-HIAA (a serotonin metabolite). Serotonin is related to mood stability. Li+ also reduces catecholamine activity in the brain (associated with brain activation and mania), by enhancing reuptake and reducing release. Therapeutically useful amounts of lithium (~ 0.6 to 1.2 mmol/l) are only slightly lower than toxic amounts (>1.5 mmol/l), so the blood levels of lithium must be carefully monitored during treatment to avoid toxicity.
Common side effects of lithium treatment include muscle tremors, twitching, ataxia[54] and hypothyroidism. Long term use is linked to hyperparathyroidism[55], hypercalcemia (bone loss), hypertension, kidney damage, nephrogenic diabetes insipidus (polyuria and polydipsia), seizures[56] and weight gain.[57] Some of the side-effects are a result of the increased elimination of potassium.
There appears to be an increased risk of Ebstein (cardiac) Anomaly in infants born to women taking lithium during the first trimester of pregnancy.
According to a study in 2009 at Oita University in Japan and published in the British Journal of Psychiatry, communities whose water contained larger amounts of lithium had significantly lower suicide rates[58][59][60][61] but did not address whether lithium in drinking water causes the negative side effects associated with higher doses of the element.[62]
6.2 Other uses
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