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A second technology that has aided in the production of environmentally clean copper is that of bacterial leaching or bioleaching. This is used as an adjunct to the SX/EW process in situations where sulfide copper minerals must be leached. Modern commercial application of bacterial leaching began in the 1950s at Kennecott39;s Bingham mine near Salt Lake City, Utah. It was noticed that blue copper containing solutions were running out of waste piles that contained copper sulfide minerals a condition that should not have happened in the absence of powerful oxidizing agents and acid. On investigation it was found that naturally occurring bacteria were oxidizing iron sulfides and the resulting ferric sulfate was acting as an oxidizer and leachant for copper sulfides. These bacteria were given the name ferrooxidans for their action in oxidizing iron sulfides. A second set of bacteria were also identified and given the name thiooxidans for their action in oxidizing sulfur to yield sul...
The SX/EW process has provided the copper industry with a tool that makes the extraction of copper from its ores significantly more environmentally friendly than by the use of the conventional smelting process. While the SX/EW process was adopted by the industry to take benefit from the sulfuric acid that the smelting process produced steps are being take to divorce the two. The Phelps Dodge Mining Company, for example, at its Morenci, Arizona mine, has completely disassembled its smelter and has converted the mine to a mine for leach operation. Details of this are given in a separate Innovations paper.
R. Brantley Sudderth, Vice President Cognis Corporation, Tucson, Arizona SX reagents Sharon K. Young, President, VersiTech Corporation, Tucson, Arizona SX/EW processing CRU, The Ten Year Outlook for Copper, 1998, CRU International Ltd., London, UK. and Exton, PA, USA. Confidential Report BHA, The Impact of SxEw Production on the Copper Industry, 1994, Brook Hunt Associates, Ltd., Addlestone, Surry, UK. Confidential Report Brierley, J.A., Expanding role of microbiology in metallurgical processes, Mining Engineering 52, No. 11, 2000, pp 49 53. Tilton, J. E. and H. H. Lansberg, Innovation, Productivity Growth and the Survival of the U.S. Copper Industry,1997, Discussion Paper No. 97 41, Resources for the Future, Washington, D.C.
The ore is removed from the ground in either open pit or underground mines. Underground sinking a vertical shaft into the earth to reach the copper ore and driving horizontal tunnels into the ore. Open pit 90% of ore is mined using the open pit method. Ores near the surface can be quarried after removal of the surface layers.
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The ore is enriched using a process called froth flotation. Unwanted material sinks to the bottom and is removed.
This is where the chemical reactions start. The powdered, enriched ore is heated in air between 500°C and 700°C to remove some sulphur and dry the ore, which is still a solid called calcine.
A flux is a substance which is added to the ore to make it melt more easily. The solid calcine is heated to 1200°C and melts. Some impurities are removed forming a matte .
Air is blown into the liquid matte forming blister copper, so called because the gas bubbles trapped in the solid form blisters on the surface.
The copper is purified to 99.99% by electrolysis. The production route described above shows the progression from a rock containing about 0.2% copper to a copper cathode of 99.99% purity.
Leaching offers an alternative to copper mining. First, the ore is treated with dilute sulphuric acid. This trickles slowly down through the ore, over a period of months, dissolving copper to form a weak solution of copper sulphate. The copper is then recovered by electrolysis. This process is known as SX EW . Advantages of these processes are: 1. Much less energy is used than in traditional mining 2. No waste gases are given off 3. Low capital investment 4. Ability to be operated economically on a small scale. It can be used on ore with as little as 0.1% copper for this reason leaching extraction is growing in importance. It is estimated that SX EW will represent 21% of total copper refined production in 2019.
Another important source of copper is recycled scrap, described as secondary copper production. Around half of Europes copper demand is currently met with recycled material, making an important contribution to the circular economy. To read more about copper recycling, click here.
Dissolution of copper from ore in sulfuric acid solvent, collection of solvent for cementation or solvent extraction Remove copper from pregnant Ieachate and remove some impurities Remove copper from pregnantIeachate and produce an electrolyte with sufficient copper content foreiectrowinning Recover copper from the loaded electrolyte
Copper Extraction Process. Copper Extraction Process plant includes Jaw crushers, conveyor belt, vibrating screen, ball mill, jig machine, spiral classifier, mixing tank, shaking table, flotation machine, slurry pump, ceramic filter, dewatering screen, tailings dewatering.