Metallurgy - Minerals Ore: deposit that contains enough...

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Minerals • Ore: deposit that contains enough metal that we can extract economically. • Most metals are found in minerals. • Names of minerals are usually based on the location of their discovery. • Other minerals are named after their colors: malachite comes from the Greek malache (the name of the tree with very green leaves). • Most important ores are oxide, sulfide and carbonates.
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OCCURRENCE OF METALS 1) Elemental Form e.g. Ag, Au, Pt – noble metals. 2) Aluminosilicates and Silicates Metal + Al, Si, O e.g. Beryl = Be 3 Al 2 Si 6 O 18 Hard to extract metals. 3) Nonsilicate Minerals Oxides – Al 2 O 3 , TiO 2 , Fe 2 O 3 Sulfides – PbS, ZnS, CuFeS 2 Carbonates – CaCO 3
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METALLURGY Metallurgy is the process of obtaining a metal from its ores. Ore is a natural deposit containing the metal. Gangue is the undesirable material in the ore, e.g. sand, clay.
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Metallurgy • Metallurgy is the science and technology of extracting metals from minerals. • There are five important steps: – Mining (getting the ore out of the ground); – Concentrating (preparing it for further treatment); – Reduction (to obtain the free metal in the zero oxidation state); – Refining (to obtain the pure metal); and – Mixing with other metals (to form an alloy).
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Steps in Metallurgy 1) Preliminary treatment to concentrate ore: Floatation. 2) Further purification and reduction to obtain the metal in its elementary state: Hydrometallurgy – leaching. Pyrometallurgy – roasting, smelting. Electrometallurgy. 3) Final purification and refining of the metal.
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ROASTING Roasting – heating in air: a) Burns off organic matter. b) Converts carbonates and sulfides to oxides: 2ZnS(s) + 3O 2 (g) 2ZnO(s) + SO 2 (g) PbCO 3 (s) PbO(s) + CO 2 (g) c) Less active metals are often reduced HgS(s) + O 2 (g) Hg(l) + SO 2 (g)
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• Pyrometallurgy: using high temperatures to obtain the free metal. • Several steps are employed: – Calcination is heating of ore to cause decomposition and elimination of a volatile product: PbCO 3 ( s ) PbO( s ) + CO 2 ( g ) – Roasting is heating which causes chemical reactions between the ore and the furnace atmosphere: Pyrometallurgy
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Metallurgy - Minerals Ore: deposit that contains enough...

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