Currently, the most common source of copper ore is the mineral chalcopyrite (CuFeS2), which accounts for about 50% of copper production. The focus of this article is on the process of copper extraction from chalcopyrite ore into pure metal.
For economic and environmental reasons, many of the byproducts of extraction are reclaimed. Sulfur dioxide gas, for example, is captured and turned into sulfuric acid — which is then used in the extraction process.
Most copper ores contain only a small percentage of copper metal bound up within valuable ore minerals, with the remainder of the ore being unwanted rock or gangue minerals, typically silicate minerals or oxide minerals for which there is often no value. The average grade of copper ores in the 21st century is below 0.6% Cu, with a proportion of ore minerals being less than 2% of the total volume of the ore rock. A key objective in the metallurgical treatment of any ore is the separation of ore minerals from gangue minerals within the rock.
Biomining is a new approach to the extraction of desired minerals from ores being explored by the mining industry in the past few years. Microorganisms are used to leach out the minerals, rather than the traditional methods of extreme heat or toxic chemicals, which have a deleterious effect on the environment.
Using a bacterium such as Thiobacillus ferrooxidans to leach copper from mine tailings has improved recovery rates and reduced operating costs. Moreover, it permits extraction from low grade ores - an important consideration in the face of the depletion of high grade ores.
The potential applications of biotechnology to mining and processing are countless. Some examples of past projects in biotechnology include a biologically assisted in situ mining program, biodegradation methods, passive bioremediation of acid rock drainage, and bioleaching of ores and concentrates. This research often results in technology implementation for greater efficiency and productivity or novel solutions to complex problems. Additional capabilities include the bioleaching of metals from sulfide materials, phosphate ore bioprocessing, and the bioconcentration of metals from solutions. One project recently under investigation is the use of biological methods for the reduction of sulfur in coal-cleaning applications. From in situ mining to mineral processing and treatment technology, biotechnology provides innovative and cost-effective industry solutions.
Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)
For more information (background, pictures, experiments and references): Copper Extraction Techniques