Copper

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Copper
Chemical formula Cu
Atomic Number 29 
OTP appearance reddish solid 
Molar Mass(g/mol) 63.54 
Melting Point(°C) 1085 
Boiling Point(°C) 2562 
Density(g/cc)
Coefficient of Thermal Expansion(×10-6 °C-1) 17
NFPA 704
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Copper is one of the seven metals of antiquity, and a key early workable metal.

Uses

Primary

  • Structural Material
  • Feedstock for Brass and Bronze
  • Essential for electrical wire

Secondary

  • WHO LEM component: IUD

Natural Sources

  • elemental copper occurs in nature, but rarely
  • -hydroxide and -carbonate coexist as the minerals malachite and azurite
  • -sulfide occurs as the mineral chalcopyrite and chalcocite.

Hazards

Production

Smelting

  1. Roast malachite or azurite at or above 290°C driving off carbon dioxide and water, producing copper (II) oxide
    CuCO3 + Cu(OH)2 2 CuO + CO2 + H2O
  2. Carbothermically reduce the copper (II) oxide to copper.
    CuO + C
    {
    red heat}
    Cu + CO // A massive excess of carbon is recommended (3:2 ubm)

Example:

221g of malachite roasts to 79 grams of copper oxide reduces to 63g of copper.

Purification

High purity is achieved by electrowinning: impure copper bars are submerged in a bath of copper sulfate and/or sulfuric acid, and a positive charge is applied at approximately 2-2.5V. The copper transits the salt bath and reforms as pure copper at the cathode. The cathode can be formed from previously purified copper, impure copper or a second metal. If the latter, the cathode is slowly withdrawn from the bath, leaving a pure copper plate behind.

The "anode sludge" deposited on beneath the anode may contain a variety of valuable metals, and should be recovered, analyzed, and either recycled or processed.

Testing

Storage

Disposal

  • Pure copper is safe to dispose of, generally.
  • Copper salts can (usually) be converted to basic copper carbonate, which is the natural mineral form. From there it can be smelted back to copper, or disposed of.
  • Copper salts, even mineralized, should not be disposed of in waterways or watersheds.

See Also

References