Because gold is an unreactive element, there is a limited number of compounds in nature, it can be free or associated with other mineral phases, such as sulfides.
Among the metallurgical processes exists the recovery of values due to adsorption and desorption of activated carbon.
In most of the times this method consists of the following steps:
The rich solution is pumped from the sinks to the adsorption circuit, generally located at short distance from them.
Within this circuit an antifouling is added, to ensure the continuous flow of the solution, then it is passed to the carbon columns where the values are trapped by the activated carbon.
The injection of the rich solution to the columns is carried out on the bottom countercurrent to avoid the compaction of the coal at the bottom of the column and the exit of the same solution is passed to the next column by the upper part, the batteries of carbon columns can be of different sizes and quantities as required, usually have between four and five and there can be more than one column circuit.
Once the values in the carbon are recovered, the poor solution or barren is pumped back to the previous process; in most cases to the leach pads, adding cyanide and lime to reactivate it.
The carbons loaded with the values are washed with hydrochloric acid, to remove impurities and are pumped into the stripping tank where soda and cyanide are added creating caustic cyanide, which strips the carbon of the values and is stored to move on to the next phase of the process, usually in electrolytic cells.
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