Metallurgy of Key Minerals - Thanatia: The Destiny of the Earth's Mineral Resources - page 223

is done with spiral concentrators in order to remove the lighter materials followed
by magnetic separators to remove the rutile and ilmenite ores. Zircon has its own
commercial market and only a very limited percentage is smelted for producing the
metal it contains 20 .
Since zirconium's properties are chemically and physically similar to titanium's
the production of zirconium and its sister metal hafnium may follow the Kroll
process (See also Sec. B.2.70). The Kroll process for zirconium starts with a carbo-
chlorination reaction in which zircon reacts with coke as a reducing agent to produce
zirconium/hafnium tetrachlorides in a fluidised bed process. These chlorides are
subsequently condensed and can be separated from each other by selective solvent
extraction. Molten magnesium and magnesium chloride in an argon atmosphere are
then used to reduce the chloride to its metal. The product is then converted into a
fine metal in a vacuum arc refining process. (IPPC, 2009).
According to Kellogg (1977), without specifying how much of this energy cor-
responds to the processes of concentration or refining, the production of sponge
zirconium requires 1,371.5 GJ/t.
Given that hafnium is also obtained by the Kroll process and energy consumption
for its production is 633 GJ/t (Kellogg, 1977), Botero (2000) took the hafnium
refining stage consumption to be identical to that of zirconium's. The remaining
738.5 GJ/t corresponds to the process of mining and ore concentration.
8.12 Lithium and Magnesium
The alkaline metals such as lithium, sodium and potassium, and the alkaline earth
metals such as calcium, strontium and magnesium all have similar chemical proper-
ties. A limited market interest exists for them as pure metals, with the exception
of magnesium. Their chlorides, oxides or carbonates however play a central role
in many industrial processes. In this section the authors only concentrate on two
metals: lithium and magnesium whose importance in new emerging technologies
deserves special attention.
8.12.1 Lithium
Lithium in the Earth's crust is as abundant as zinc and more common than either
lead or tin but is widely dispersed. This effectively means that whilst scarcity per
se is not a problem, the number of exploitable deposits are relatively few. The ones
that are commercially viable occur in brines, sedimentary rocks and igneous rocks in
pegmatite deposits. The latter are mostly silicates and include spodumene, lepido-
lite and petalite which are combined silicates of aluminium, lithium and potassium.
They can all be used to recover lithium, although this is currently uncompetitive
20 See http : ==www:mineralszone:com=minerals=zirconalliedmineral:html. Accessed Nov.
2011.