Toxic Hazards of Cyanide in Gold Recovery

Metal recovery and processing can pose some significant toxicological hazards. One such potential hazard is from cyanide (CN ), which is used to extract gold (chemical symbol Au) from low-grade ores. In such ores, the gold is present in the elemental form, but it is so finely divided and dispersed that it cannot be separated mechanically from the ore. To extract the gold, the ore is leached with a solution of sodium cyanide in the presence of atmospheric air, for which the reaction is as follows  

The gold is then chemically precipitated from the dissolved Au(CN)2 in the leachate solution. 

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