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Deadly cyanide need no longer be used in gold mining, say Australian
scientists. After gold ore has been crushed, it is washed in cyanide to lock the
gold up in the form of gold cyanide ions, which are absorbed by porous activated
carbon before the gold is extracted. But physicists at Monash University have
worked out how to use chloride which is much less harmful than cyanide.
Normally, chloride would let go of the metal as soon as it encountered the
carbon, making purification tough, but the Monash team has identified a type of
activated carbon which keeps the gold chloride ion intact. Using chloride would
greatly reduce the threat of environmental damage from spills, such as the
recent disaster on the Danube.