Abstract: A process for removing cyanide anions from waste waters using halogen-free ferric salts is disclosed. The process is particularly effective when treatment of cyanide waste waters is done by adding ferric sulfate while adjusting pH of the waste waters with a halogen-free acid, such as sulfuric acid, to a pH ranging from about 3.0 to 5.0.The ferric ferricyanides formed are agglomerated and flocculated using synthetic polymers along with whatever other dispersed or suspended solids may be present in the waste waters, and this dense sludge is separated in a clarifier. Cyanide removal is at least 80%, relative to initial cyanide concentrations, and preferably 90% removal or higher.Cyanide wastes from coke oven off gas scrubbing waters are particularly waste waters amenable to this treatment.