![]() Sulfide ores are generally processed using pyrometallurgy, the extraction and purification of metals by processes involving the application of heat. Positively-charged copper ions (called cations) come out of solution and are plated onto a cathode (negative electrode) as 99.99% pure copper. An electrical current passes through an inert anode (positive electrode) and through the copper solution from the previous step, which acts as an electrolyte. ![]() The last step is called electrowinning, a type of electrolysis. The leftover leach solution is then recycled, by adding additional acid and sending it back to the sprinklers in the heap leaching process.Įlectrowinning is the final step in processing oxide ore into copper cathodes. The two liquids are then allowed to separate based on solubility, with copper remaining in solution in the solvent, and impurities remaining in the leach solution. The copper migrates from the leach solution into the solvent. The pregnant leach solution is mixed vigorously with a solvent. The second step is solvent extraction, in which two immiscible (un-mixing) liquids are stirred and allowed to separate, causing the cooper to move from one liquid to the other. The copper compound can now be seen at concentrations of between 60-70%. The resulting “pregnant” leach solution of sulfuric acid and copper sulfate is collected in a small pool. The leaching reagent (dilute sulfuric acid) is sprayed through sprinklers on top of the heap pile and allowed to trickle down through the heap, where it dissolves the copper from the ore. Following mining, transporting, and crushing to a consistent gravel or golf ball-size, the crushed ore is piled into a heap on top of an impenetrable layer, on a slight slope. Heap leaching is very commonly used for low-grade ore, which would otherwise not be economical to send through a milling process. Heap Leaching is the process of using percolating chemical solutions to leach out metals. Heap Leaching and Solvent Extraction of Oxide Ore. This process uses aqueous (water-based) solutions to extract and purify copper from copper oxide ores at ordinary temperatures, usually in three steps: heap leaching, solvent extraction, and electrowinning. Oxide ores are generally processed using hydrometallurgy. This primary crusher reduces the size of the ore from boulder to golf ball-sized rocks. Most ores are then sent through a primary crusher, which is typically located very close to or sometimes in the pit. The size of the equipment needed to haul the tons and tons of ore is gigantic. The resulting boulders are then ready for hauling specialized haul trucks, conveyors, trains, and shuttle cars can all be used to haul the ore from the blasting site to the processing site. ![]() To remove the ore, boring machinery is used to drill holes into the hard rock, and explosives are inserted into the drill holes to blast and break the rock. Copper mining is usually performed using open-pit mining, in which a series of stepped benches are dug deeper and deeper into the earth over time. The first steps of copper processing are the same for both ores: mining and transporting. When it is economically feasible, a mine may extract both types of copper minerals when it is not possible, mines will only process either the copper oxides or the copper sulfides. Since each mine site is unique in its mineral composition, concentration, and quantities, the most economical and profitable processing of ore must be determined by the mine planners. ![]() Although the processing costs are higher, ultimately more copper can be extracted. On the other hand, while copper sulfide ores are less abundant, they contain higher amounts of copper. Although this requires more ore to be extracted and processed, this process is less expensive, so oxides can still be mined at a profit. Copper oxides are more abundant near the surface, but are considered low-grade ore, with a lower concentration of copper. The most common types of ore, copper oxide and copper sulfide, undergo two different processes, hydrometallurgy and pyrometallurgy, respectively, due to the different chemistries of the ore. Oxide and sulfide ores undergo different processes to be purified into 99.99% pure copper.Ĭopper processing is a complicated process that begins with mining of the ore (less than 1% copper) and ends with sheets of 99.99% pure copper called cathodes, which will ultimately be made into products for everyday use. ![]()
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