While it is important to maximize the adsorption of gold from the solution, it is equally as important to subsequently desorb the gold from the carbon. Any molecules that remain adsorbed after elution or stripping translate into gold that cannot be recovered. As a result, it is important to select an activated carbon that efficiently adsorbs and desorbs to maximize overall yield and profitability.
Activated carbon is a highly porous organic material comprised of a series of graphitic plates, which are interconnected by carbon-carbon bonds. This creates a highly porous structure and gives an extensive internal surface area, where "adsorption" occurs. Adsorption is a surface reaction that causes
compounds to "stick" to the surface of the carbon. The phenomenon is the result of intermolecular attractions or forces inherent to the carbon surface.
It is this gold-cyanide complex that is attracted to the tremendous surface area available on activated carbon, allowing for a variety of recovery techniques. One handful of activated carbon has a surface area equivalent to that of a football field. The massive surface area of activated carbon makes the material an ideal adsorbent. Gold alone is not soluble, and will not be readily adsorbed by activated carbon until it is cyanidated, forming a gold-cyanide coordination complex called dicyanoaurate.