Cyanide

A cyanide is any chemical compound that contains the group C≡N, with the carbon atom triple bonded to the nitrogen atom. Inorganic cyanides contain the highly toxic cyanide ion CN- and are the salts of the acid hydrogen cyanide (HCN). Organic cyanides contain the cyano group (CN) single-bonded to another carbon atom are also known as nitriles. Two cyanide ions can bond to each other via their carbon atoms, forming the gas cyanogen (NC-CN).

Mining

Cyanide salts are used in silver and gold mining, called the cyanide process. The high grade ore is finely ground and mixed the cyanide solution (concentration of about two kilogram NaCN per tonne (1000 kilograms)) or low grade ores are stacked into heaps and sprayed with cyanide solution (concentration of about one kilogram NaCN per tonne (1000 kilograms)). The precious metal cations bind to the cyanide anions and form a soluble cyanide. The pregnant liquor is separated from the left-over dirt which is discarded to a tailing pond or spent (the recoverable gold having been removed) heap. The metal is recovered from the pregnant solution with zincdust that replace the gold in solution or by adsorption onto activated carbon. This process can result in environmental and health problems. Cyanide is highly reactive; it decomposes rapidly in sunlight. It can mobilize some heavy metals like mercury (if mercury is present). Gold can also be associated with arsenopyrite, which is similar to iron pyrite (fool's gold), with iron replaced by arsenic.

Related Topics:
Silver - Gold - Cyanide process - Cation - Anion - Zinc

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