METHOD OF RECOVERING GOLD AND SILVER FROM MATERIAL CONTAINING NONFERROUS METALS AND IRON Russian patent published in 1998 - IPC

FIELD: hydrometallurgy of precious metals. SUBSTANCE: material is leached in presence of oxygen by potassium cyanide solution, namely by solution prepared by dissolving urea and potash in water. Cyanide solution obtained is returned into the starting material leaching stage until it becomes saturated with respect to gold and silver. Precipitate is filtered off and used in the further complex processing. Gold and silver-saturated solution is treated by potassium ferrate to precipitate hydroxides of gold, silver, nonferrous metals, and iron. Precipitate is separated from potassium hydroxide solution by filtration. Solution is evaporated to form KOH crystals and vapors of water. The latter are condensed and condensate is used for dissolving urea and potash caking product. Precipitate containing hydroxides of gold, silver, nonferrous metals, and iron is leached by ammonia water to dissolve silver, nonferrous metals, and iron, after which gold precipitate is filtered off and submitted to isolation of gold therefrom. Filtrate is further used to isolate silver by cementation with iron. EFFECT: achieved closed, wasteless, environmentally safe technology with no secondary pollution. 1 dwg , 1 tbl