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Method of extracting copper and gold by bacterial leaching.

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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 bacteria?. 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- ions?, are added to the copper ore. The bacteria in the acidic leaching solution then convert the insoluble sulphide minerals into a solution containing Cu2+, Fe2+, Fe3+ and SO42- ions. The acidic solution provides the optimum pH for the bacteria to work at. Following the bacterial action, the solution is drained off of the impermeable rock or pumped out of the ground through the remaining holes and the remaining solution prepared for concentration and extraction of the Cu2+ ions. Extraction and stripping then occur, here the copper ions are selectively removed from the leaching solution by the "ligand exchange solvent extraction? ...read more.


and the gold atoms dissolve in the cyanide and the oxygen then causes the formation of sodium cyanoaurite and sodium hydroxide? which are solids and then separated from them through absorption by carbon. 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 particles? can be different, for example sulpholobus acidocalderius was used during research by King's College Advantages and disadvantages of using bacterial leaching over traditional methods There are many advantages of using bacterial leaching which are associated with both gold and copper, for instance tailings from traditional methods and very low grade ore can be used which increases the mining company's profit and decreases the detrimental effects of mining on environmental appearance. Environmental advantages also include that the bacteria used can be recycled for reuse, decreasing expenditure. In some cases the use of bacterial leaching means that excavation need not occur because the bacteria can be pumped into holes in the ground, left to oxidise the ores and then pumped out through other holes. ...read more.


Additionally, even with no gold recovered, other metals that are recovered such as copper, nickel, cobalt and zinc produce an economically competitive mine?. Bacterial leaching is also effective over a wide range of temperatures and pHs?, meaning that it can be used throughout the world, this also applies to the financial ease of production. There are no specific disadvantages of using bioleaching to extract gold. I suggest that the reason that bioleaching is the primary extraction method of gold and only a secondary method for copper is that copper mining companies are reluctant to take into account the long production time and gold mining companies are attracted by the significantly increased recovery. Developmental stages of new mining processes prior to commercial use In order for a new mining process to become commercial, funding must be found for essential research to ensure that the process is economical for the company?. Pilot plants must be tested in locations where the mine is likely to be placed and a thorough environmental impact assessment carried out to ensure that the processes do not cause undue environmental damage?. Finally governmental permission must be obtained before commercial activity can take place?. ...read more.

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