| Lithium is a silvery white metal. It is the lightest metal known to man and belongs to the alkali metals. Being an alkali metal, it is extremely reactive, in particular with oxygen. The name lithium comes from the Greek word “lithos”, meaning stone. Unlike other Group I metals, lithium is believed to have been discovered yin mineral form, while the potassium and sodium were first found in plants. Discovery The discovery of lithium was attributed to the Swede Johan A. Arfvedson, who first identified it in 1817 while analysing the mineral petalite. Although it was first discovered in 1817, it was not until 1855 when Sit Humphrey Davy and William Thomas Brande were able to isolate it through the electrolysis of lithium chloride. The first commercial production of lithium took place in Germany in 1923 when Metallgesellschaft AG used electrolysis to treat a molten mixture of lithium and potassium chlorides. Occurrence Due to its high reactivity lithium is not found in its native state. It’s main sources are igneous rocks and brine. The main igneous rocks used as sources of lithium are: • Spodumene (LiAlSi2O6) – The most abundant and important of the lithium containing ores. Found in North America, Brazil, USSR, Spain, Africa, and Argentina. • Lepidolite (K2Li3Al4Si7O21(OH,F)3) – Found in Canada and Africa. • Petalite (LiAlSi4O10) – Found in Africa and Sweden. • Amblygonite LiAl(F,OH)PO)4 - not a common source of lithium Lithium is also extracted from brine by evaporation. Places where this occurs include Searles Lake (California, USA) and Clayton Valley (Nevada, USA). Extraction Lithium is most commonly extracted from spodumene. Naturally occurring β- spodumene is converted α-spodumene by heating to 1100˚C. α-spodumene which is less dense is crushed and then mixed with sulphuric acid and heated to 250˚C, and extracting it into water producing a lithium sulphate (Li2SO4) solution. It is then treated with soda ash to form lithium carbonate. The carbonate is then reacted with hydrochloric acid (HCl) to convert it to the chloride which can then be processed into lithium metal by electrolysis. Other techniques utilising spodmene to produce lithium carbonate that can be further processed into lithium metal include: • Alkaline fusion of spodumene followed by carbonation to produce lithium carbonate • Acid roasting, calcination and subsequent carbonation to produce lithium carbonate. As mentioned above, brine can be an energy efficient source used to produce lithium carbonate, from which lithium metal can be yielded. This is now the most common origin of lithium metal. |