Refining Of Gold
Refining of gold forms the final stage in gold production, after the mining processes. When gold is mined it is found in veins inside the earth. Gold is also found in placer deposits and is extracted by power shovelling and dredging. Gold is separated from the ore by using several methods.
Refining of gold can be done by three processes which are carbon-in-pulp, cyanidation and floatation. Depending on the purity required these methods can be used independently or in a combination. In the floating method the powdered ore is put into a solution which has an agent to create froth, an agent for collecting the gold and chemicals which will separate the contaminants. The solution is made to froth by the blowing in air bubbles so that the collecting agent along with the gold can stick to the air bubbles. The chemicals in the solution will keep the contaminants from sticking to the bubbles. The froth containing the gold is then removed from the surface.
Refining of gold by cyanidation involves use of chemicals to precipitate the gold from the ore. The powdered ore is immersed in a tank having a cyanide solution. Zinc is then introduced to create a reaction which precipitates the gold. The solution is then filtered to separate the gold from the solution.
Amalgamation is a process similar to cyanidation using different chemicals. In this process refining of gold takes place by the solution of ore being passed over plates that are coated with mercury. An amalgam of mercury and gold is formed which is later heated so that the mercury is let off as gas and gold is left behind.
Carbon-in-pulp method for refining of gold uses carbon for gold precipitation. The powdered ore is mixed with water to make it into a kind of pulp. Then the pulp is put into a cyanide solution, which will dissolve the gold. The carbon is added so that the gold bonds with it and starts to precipitate. After that a hot corrosive solution is used to separate the carbon from the gold.
Another popular method used for refining of impure gold is smelting. Smelting is only used after the ore has been separated from the gold and if the gold needs further purification. In this method the gold is heated along with "flux" which is a chemical substance. The flux has the property of bonding with only the contaminants and a slag is formed which floats on top. This is removed and a pure gold precipitate is left behind.
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