The Method of Extracting Copper and Gold by Bacterial Leaching

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The Method of Extracting Copper and Gold by Bacterial Leaching

The methods of extracting gold and copper have significant differences and therefore require separate attention. Prior to leaching occurring, either a tailings pile must be built up upon a base of impermeable rock or a series of holes drilled into the ore, to provide access for the bacteriaα.

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At process one the bacteria thiobacillus ferro-oxidans and thiobacillus thio-oxidans, naturally occurring bacteria that obtain the energy that they need to survive by oxidising Fe2+ and S2- ionsα, are added to the copper ore. The bacteria in the acidic leaching solution then convert the insoluble sulphide minerals into a
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An electro-winning process is then carried out, whereby a current is run through the solution containing the Cu2+ ions, and pure copper atoms collect on the cathodeε.

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The extraction process for gold is different, initially froth floatation occurs to separate the tailings from the tailings and bioleaching is then carried out on the slurry of concentrate. Also the bacteria used to break down the mineral matrix surrounding the gold particlesη can be different, for example sulpholobus acidocalderius was used during research by King's College, London, researchersη. Following this cyanidation is carried out, during this process aerated sodium cyanide is blended with mixture A(see figure 2 below) and the gold atoms dissolve in the cyanide and the oxygen then causes the formation of sodium cyanoaurite and sodium hydroxideθ which are solids and then separated from them through absorption by carbon.

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Cyanidation

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Neutralisation

The extraction process for gold is different, initially froth floatation occurs to separate the tailings from the tailings and bioleaching is then carried out on the slurry of concentrate. Also the bacteria used to break down the mineral matrix surrounding the

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