Gold and Silver
Cyanidation is still the most widely used method to leach gold, using sodium or calcium cyanide as lixiviant.
An anionic gold-cyanide complex is formed that is extractable by basic resins.
Other metals present in the ore, such as silver and base metals ( copper, nickel, cobalt, zinc, iron, etc. ) are also leached in cyanide media.
Selective ion exchange resins are designed to preferentially adsorb the mono-valent gold-cyanide species.
Ion exchange resins are stripped at low temperatures and do not require energy-intensive thermal regeneration.
Ion exchange resins show high adsorption efficiencies, even in the presence of naturally occurring carbonaceous matter.
Complexes can be stripped from the columns with sodium cyanide and salts of metal cyanide compexes.