How does activated carbon remove dissolved gold from cyanide solution?

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A worker in safety gear walks beside a conveyor belt carrying ore at the Tanami gold mine in the arid, expansive landscape of the Tanami Desert. — gold processing The Tanami gold mine, Northern Territory, Australia.

In the process of gold processing, activated carbon is used to recover gold from a cyanide solution by a process known as adsorption.1

When granular activated carbon is added to the gold-bearing ore slurry, the dissolved gold ions are attracted to and adhere to the surface of the carbon particles. This technique is highly efficient because it allows for the removal of gold directly from the slurry, eliminating the need for expensive solids-liquids separation equipment.1

Once the gold has been adsorbed, the carbon is easily separated from the barren ore by passing the slurry through a screen. The gold is subsequently removed from the carbon through a process called elution, where a strong solution of sodium cyanide and sodium hydroxide is used to leach the gold back into a liquid state for final recovery via electrowinning or the Merrill-Crowe process.1