Pyrometallurgy – roasting, smelting. Electrometallurgy. 4) Final purification and
refining of the pure metal. 5) Possible mixing with other metals to form alloys.
Isolation of the Elements From their Natural state Sources of
:
Which metals can be found in nature in elemental form? (How do you know?)
What can you expect for most metals?
CHEM112 LRSVDS Metallurgy
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Modern Materials: Metals and Alloys Most metals are found in minerals. 1) Some are found in Elemental Form Ag, Au, Pt, Ru, Rh, Os, Ir (noble metals) 2) Aluminosilicates and Silicates Metal + Al, Si, O e.g. Beryl = Be3Al2Si6O18 Hard to extract the metals 3) Nonsilicate Minerals Oxides – Al2O3, TiO2, Fe2O3 Sulfides – PbS, ZnS, CuFeS2 Carbonates – CaCO3 4) Salts Active Metals – Group I, II Not found in nature as pure metals, always combined with other elements (e.g. salts in the ocean, minerals); WHY? CHEM112 LRSVDS Metallurgy
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Steps in Metallurgy Metallurgy is the science and technology of extracting metals from minerals. 1)! Mining getting the ore out of the ground 2)! Concentrating the ore: prepare for further treatment Floatation Hindered settling Magnetic separation 3)
Further purification and reduction to obtain the metal in its elementary state (zero oxidation state): Hydrometallurgy – leaching Pyrometallurgy – roasting, smelting Electrometallurgy
4)! Final purification and refining of the pure metal 5)! Possible mixing with other metals to form alloys CHEM112 LRSVDS Metallurgy
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Hydrometallurgy Metal is extracted from ore using aqueous reactions Leaching: Dissolution agent: acid, base, salt. Example: Dissolve Au by forming a complex ion with CNKf [Au(CN)2] ! = 2 x 1038
Gold metal is then obtained by reduction: 2Au(CN)2!(aq) + Zn(s) ! CHEM112 LRSVDS Metallurgy
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Hydrometallurgy of Aluminum •! Aluminum: •! Bauxite: Al2O3.xH2O Bauxite contains impurities:
Bayer Process •! Bayer process: bauxite (~ 50 % Al2O3) is concentrated to produce aluminum oxide. •! Selective precipitation of Metal salts: –! Dissolve bauxite in strong base (NaOH) at high T, P Al2O3 dissolves ! [Al(H2O)2(OH)4]hydrated metal complex –! Filter out insoluble solids Fe2O3, SiO2 do not dissolve –! Next lower the pH, Al(OH)3(s) precipitates. WHY? CHEM112 LRSVDS Metallurgy
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Hydrometallurgy of Copper •!One important use of copper metal:
•!Are impurities important in this application?
ore (CuFeS2) is processed with acid; 2CuFeS2(s) + 2H+(aq) + SO42-(aq) + 4O2(g) ! 2Cu2+(aq) + 2SO42-(aq) + Fe2O3(s) + 3S(s) + H2O \ / 2CuSO4(aq) "
Electrolyzed to Cu CHEM112 LRSVDS Metallurgy
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•!
Pyrometallurgy:
•!
Several steps are employed: Calcination:
PbCO3(s) ! PbO(s) + CO2(g) Roasting:
1.! Burns off organic matter. 2.! Converts carbonates and sulfides to oxides: 2 ZnS(s)+ 3O2(g) !2ZnO(s) + SO2(g) 3. Less active metals are often reduced HgS(s) + O2(g) ! Hg(l) + SO2(g) CHEM112 LRSVDS Metallurgy
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The Pyrometallurgy of Iron Sources of iron:
Iron Ore (Taconite) : Add limestone and coke:
Smelting:
The blast furnace CHEM112 LRSVDS Metallurgy
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Pyrometallurgy of Fe Coke: 1) fuel to heat the furnace (with O2) 2) produces gases that reduce iron 2C(s) + O2(g) ! 2CO(g) + heat heat + C(s) + H2O(g) ! CO(g) + H2(g) Fe3O4(s) + 4CO(g) ! 3Fe(l) + 4CO2(g) Fe3O4(s) + 4H2(g) ! 3Fe(l) + 4H2O(g)
CHEM112 LRSVDS Metallurgy
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Pyrometallurgy of Fe Why is limestone (CaCO3) added? •! At high T: CaCO3 ! CaO + CO2 CaO + SiO2 ! CaSiO3(l) Metal + Nonmetal ! slag oxide oxide basic acidic Purpose of Limestone (CaCO3) !! removes SiO2 (and other) impurities !! Produces slag that floats on Fe(l); protects it from oxidation by O2 CHEM112 LRSVDS Metallurgy
Uses of Slag:
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