ADSORPTION PROCESSES WITH ACTIVATED CARBON

A variety of extraction techniques are employed to liberate gold from crushed raw ore. These processes make the gold available for release into the cyanide solution. 

CARBON-IN-COLUMN 

CIC is most commonly used to recover gold from heap leaching operations, processes in which a Sodium Cyanide solution percolates through a “heap” of crushed and agglomerated ore, causing the gold to leach into the solution. The gold-bearing solution is then pumped to a series of adsorption columns containing activated Carbon. Heap leaching followed by CIC circuits is a preferred method for gold recovery from low grade surface deposits and waste rock because of its low capital and operating costs. 

CARBON-IN-PULP

In CIP operations, mined ore is milled and mixed with water and thickeners, creating a slurry of ore and water called pulp. The pulp is then pumped to air-agitated leaching vessels, where the gold is leached out of the ore using a sodium cyanide solution. The pulp is transferred to a series of adsorber tanks containing Activated Carbon, which mixes with the leached pulp and flows countercurrent to the pulp in a series of tanks. The gold-bearing activated carbon is separated from the pulp by a mesh screen that blocks the carbon from passing through, while the smaller pulp particles are filtered away. 

CARBON-IN-LEACH 

CIL operations are very similar to CIP, but activated carbon is instead added directly to the vessels in which cyanidation is taking place. CIL is an especially beneficial technique when ore contains high levels of carbonaceous material. Naturally present carbon competes with the activated carbon in adsorbing gold in a process called “preg robbing,” which causes gold losses. Therefore, in CIL, the cyanidation process is carried out simultaneously with adsorption on activated carbon, which is in direct contact with pulp in the cyanide solution. The CIL process minimizes the time that cyanidated gold can be in contact with competing carbon native to the ore.