The mining
and processing steps involved to obtain a final copper product are very energy
demanding and complex. Copper is being refined
from ores in the ground, which are usually extracted either from open pit or
underground mines. Majority of copper mines operating around the world are
extractive two types of ores: either Oxide or Sulfide Ores. In order to
separate copper from specific type of ores different processing techniques are
required.

Processing Sulfide Ores

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The process of obtaining copper from Sulfide Ores starts from
extraction of raw materials, which usually contain only from 0.25 to 0.5% of
copper, and transportation to mine processing plant, where the copper-bearing
minerals are separated from the rest of the rock by crushing and grinding. After
physical separation process, copper is being furtherly refined by froth
floatation device which produces copper concentrate containing 30% of final
product.  Next stage is called smelting,
which gives all cycle a name – pyro-processing: processing by fire, involves
hard manual labour and results in high energy consumption as all smelting plant
is operated at very high temperatures and produces large energy waste which is
not being recovered. Final stage which separates copper to 99.99% is electrolytic
refining: electricity is being passed through solutions containing copper
compounds and as a result pure copper forms on the negative electrode.

Figure 1 Processing of Sulfide Ores (Copper Development Association)

Leaching Oxide Ores with Sulfuric Acid

Opposite
to other types of ores, Oxide ores contain from 0.1 to 1.0% and being processed
purely chemically.  Ore is being
extracted from mine, transported to processing facility where it is being
dumped to pads full of acid, which leach out copper ions creating lakes of blue
copper sulfate. Next step is to collect copper
sulfate solution is to the pregnant leach pond and pump it to solvent
extraction plant where solvent extraction phase of treatment occurs in two
stages: first stage is when organic solvent is used to recover copper ions
contained in the pregnant leach solution, exchanging them with hydrogen ions in
the acid. Next stage is a solution from which copper is being refined
and recovered into a solvent, which is then being electrolytically refined to a
process called solvent extraction and electrowinning (SX-EW). Finally, the electrowinning plant uses electrolysis to collect
copper onto steel cathodes with inert lead anodes being used.

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