Copper

 

Copper

Chemical formula	Cu
Atomic Number	29
OTP appearance	reddish solid
Molar Mass(g/mol)	63.54
Density(g/cc)	9
Melting Point(°C)	1085
Boiling Point(°C)	2562
Coefficient of Thermal Expansion(×10-6 °C-1)	17
NFPA 704	1 1 0

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.

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 If the latter, the cathode is slowly withdrawn from the bath, leaving a pure copper plate behind.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.

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

• Gorgievski, M1; Bozić, D; Stanković, V; Bogdanović, G. (2009) "Copper electrowinning from acid mine drainage: a case study from the closed mine 'Cerovo'"
  Journal of Hazardous Materials 170(2-3); pp716-721. 
  DOI:10.1016/j.jhazmat.2009.04.135
  link courtesy United States National Institutes of Health.
• Roberts, H. S.; Hastings Smyth, F. (1921) "THE SYSTEM COPPER: CUPRIC OXIDE: OXYGEN"
  Journal of the American Chemical Society 43(5); pp1061–1079. 
  DOI:10.1021/ja01438a009
  link courtesy Google Books.