Degussa Aktiengesellschaft

Annette Ziegler

Juergen Loroesch

Helmut Knorre

Manfred Diehl

Norbert Steiner

Karl-Heinz Koenig

Eckhart Krone

Jochen Ullmann

Steven Gos

Mathias Stoll

A process is disclosed for the leaching of gold and silver from ores and ore concentrates through intimate contact of the ore or ore concentrate with an aqueous leach solution containing cyanide. The leach solution has a pH of 8 to 13. The leaching process takes place in the presence of an oxygen-releasing peroxo compound. The separation of the formed cyano complexes of gold and silver takes place in a known manner. During leaching, at least one peroxoborate compound is present, in an effective quantity, as the peroxo compound. The peroxoborate is preferably a sodium or calcium peroxoborate. Compared to previously known leaching techniques in the presence of hydrogen peroxide or calcium peroxide, the leaching process according to the present invention provides a higher and/or faster precious metal yield and/or minimizes the consumption of cyanide and/or oxidizing agent.

Process for leaching of precious metals

A process for leaching gold and silver from ores and ore concentrates is disclosed using a cyanide leaching solution and hydrogen peroxide and maintaining an oxygen concentration of 2 to 20 Mg of O.sub.2 /liter. In the invention, leaching takes place in the presence of decomposition catalysts and preferably the formed cyano-complexes are separated during leaching from the leach solution. Decomposition catalysts are manganese compounds, present as 0.01 to 1 mg computed as Mn/liter of barren solution, or 1 to 50 mg computed as Mn per kg of ore slurry, or they are inorganic or organic polymers or carbon. Activated charcoal is preferred and simultaneously adsorbing cyano-complexes of precious metals. The process offers lowered consumption of H.sub.2 O.sub.2 and possibly cyanide and maximum gold yield in a shortened leaching time.

Process for leaching precious metals with hydrogen-peroxide and a

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Offenbach, Germany

Annette Ziegler