| Metallurgy: Modern Extraction of Copper Continued | |||||||||||||||||||
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A hot furnace containing Chalcopyrite (CuFeS2), copper mixed with iron and sulfur, is filled with hot air that blows over the ore. This begins separating the copper from other particles in the ores, mainly sulfur and iron. The iron reacts with oxygen to form iron oxide as does the sulfur in creating sulfur dioxide. 2CuFeS2 + 3O2 = 2FeO + 2SO2 + 2CuS. These are let out of the furnace though openings and removed from the system. Silicate is added to the liquid copper and remaining iron to form iron silicate (FeO + SiO2 = FeO + SiO2), or slag, which is the waste from the reaction. This let out through a tube placed at a certain height that corresponds to how high it floats above the copper, which is based on how much of the reaction the furnace can handle at once. Since the slag is lighter than the copper floats above it and the liquid copper sits below. The result is a molten hot liquid called matte, which is further refined by blowing air through it (Cu2S + O2 = 2Cu + SO2), burning impurities out. The now 98% pure copper, called blister copper, undergoes one final procedure before being entirely pure, electrolysis. The slab of blister copper is suspended in a solution of copper sulfate and sulfuric acid. Equations for Extracting Copper from it's Ores |
Here, the blister copper slab acts as the positive anode and a negatively charged cathode is placed on the other side of the container. An electrical current is passed through the solution, separating the copper from the anode. The copper is now attracted to the cathode where it can be collected and the copper can used for one of it's many purposes. Click HERE to see a visual of this process. However, not all forms of copper come in the form of chalcopyrite, much of the copper that is extracted comes from copper oxide (CuO) ores. To separate the copper from the ore, a process known as leaching is used. Leaching is successful because the sulfuric acid that is sprayed over the rock dissolves the copper, but not the rock from which it came. A solution of copper sulfate is formed (CuO + H2SO4 = CuSO4 + H2O), from the copper that is dissolved and the sulfuric acid, which can be purified by electrolysis, where the Copper Sulfate is broken up leaving only the copper. |
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