Many of us are fairly familiar with the uses of copper, from wiring to providing us with corrosion resistant tubing for plumbing, but do we know how this precious metal comes into our lives?
Copper starts its lifecycle as various ores, being mostly mined throughout South American countries such as Peru, Argentina, and most importantly, Chile. These ores typically have between .5 and 2% copper, which is extracted by various methods depending on ore type and cost.
Sulfide ores (Cu2S, CuFeS2,and CuS), usually employ smelting in order to extract the ore. The ore is first crushed into a fine powder, leaving remaining metals at roughly 27% iron, 33% sulfur, and 30% copper. The ore is then mixed with reagents that make the copper hydrophobic, after which it is introduced to water. The copper simply separates from the mixture and rises to the top with the help of jet streams of water.
At this point, the remaining solution is introduced to a furnace kept between 500-700 degrees Celsius, which burns any sulfides left behind. The mixture is still not pure, so fluxes are added to this copper, before the furnace is fired again, to 1200 degrees Celsius. The fluxes combine with unwanted compounds, allowing for easy extraction.
Next, liquid matte is oxidized in order to remove iron and burn off any remaining sulfide as sulfur dioxide. This produces 97-99 percent pure blister copper, as the copper is given blister holes by the escaping Sulfur Dioxide gas.
The last stage of copper production is to anodize the copper and treat it with electrolysis, where a pure copper sheet is also submerged to act as a cathode in a tank of copper sulfide and sulfuric acid, where copper ions migrate to the cathode and produce 99.9-99.99 pure copper.
The pure sheets of copper are then melted again, at which point they are deoxidized in order to prevent any defects within the casting process. The molten copper is then placed into molds to achieve the circular casts, at which point it is allowed to cool before having a hole drilled out in the center, creating the tube.
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