[LukeL]

I think ammonia is the only thing to neutralize cyanide. Ammonia itself is a dangerous gas that can kill in seconds, so the solution can be as bad as the problem.

[thackney]

Multiple methods exists including:
ALKALINE CHLORINATION,
HYDROGEN PEROXIDE,
SO2

http://www.sgs.com/en/Mining/Metallurgy-and-Process-Design/Cyanidation-Technologies/Cyanide-Destruction.aspx