Froth flotation is a method used to recover base metals like copper, zinc and molybdenum, from sulfide ores. The slurry from the grinding mills is mixed with chemical frothers and collectors in large tanks. Air is injected into the bottom of the tank to create bubbles. The bubbles are the key to separating the mineral from waste rock sand (tailings). The mineral sticks to the bubbles and rises to the top of the tank, while the tailings fall to the bottom.
The froth is collected and a sent through a series of thickeners to remove the water. The material collected at the end of the froth flotation process is called mineral concentrate.
Copper Flotation Slideshow
Smelting is type of metallurgy that is used to produce pure metal from mineral concentrate. This includes production of copper, lead and zinc, as well as precious metals like silver, and iron ore. Smelting involves melting the mineral concentrate in a furnace, along with a mixture of flux and oxygen. Flux refers to a mixture of inert minerals that controls the chemistry of the slag, the unwanted portion of smelted minerals. The portion that contains the desirable metal is called the matte. The matte is seperated from the slag and purified further. The final product of smelting is called blister. Blister copper is about 90% pure copper metal. The blister copper is made into anodes for a final refining process called electrorefining.
Copper Smelting Slideshow
Electrorefining is a method similar to electrowinning, that is used to further purify metals from the froth flotation and smelting process. Some products, like electronics, require metals to be very pure to function properly. For example, electric wires must be made from very pure copper to properly conduct electricity. The blister copper produced from smelting is only 90% pure, and contains impurities that reduce its conductivity. In electrorefining, the solution is sulphuric acid, the cathode is made of pure copper or steel, and the anode is made of impure blister copper. During electrolysis, the copper ions from the anode dissolve into the acid and transfer to the cathode. The product is 99.99% pure copper, a quality suitable for further manufacturing.
Purifying Copper Video