Degussa Aktiengesellschaft

Karl-Heinz Koenig

Peter K Kleinschmit

Karlheinz Drauz

Peter Panster

Manfred Diehl

Hermann Lotter

Norbert Steiner

Juergen Loroesch

Michael Schuster

Annette Ziegler

Eckhart Krone

Jochen Ullmann

Elske Schopenhauer-Gehrmann

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

Heavy metals can be precipitated from waste water or aqueous reaction solutions containing inorganic and/or organic complexing agents with substituted thiorureas of the general formula R.sub.1 R.sub.2 N-CS-NH-COR.sub.3. N,N-dialkyl-N'-benzoyl thioureas are used with preference, whereby methyl, ethyl, n-propyl or isobutyl groups are used as alkyl substituents.

Substituted thioureas for the separation of complexly bound heavy-metal

Organopolysiloxane products containing acyl thiourea groups and from the units: ##STR1## are disclosed. R.sup.1 stands for an optionally substituted phenyl group or an alky group and R.sup.2 and R.sup.3 for

Organopolysiloxanes containing acyl thiourea groups, methods of their

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Frankfurt-am-Main, Germany

Karl-Heinz Koenig