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The treatment of copper-gold ores by ammonium thiosulfate leaching

University of British Columbia

The application of ammonium thiosulfate for the treatment of copper-gold ores has been investigated. Leaching studies were conducted with copper minerals, copper minerals with gold addition to solution and copper-gold samples of different copper and gold grades. The behaviour of thiosulfate, tetrathionate and sulfate in solution was studied using ion chromatography. The copper sulfide minerals chalcopyrite and enargite seem to be unreactive toward an ammonium thiosulfate leach. Covellite and chalcocite leach to a slight extent in this leaching system. The copper extractions of the sulfide minerals seem to be independent of the availability of complexing agents. The copper oxide minerals cuprite and malachite showed high copper extractions in the presence of sufficient lixiviant. Experiments showed that both gold extraction and thiosulfate stability are influenced by a combination of aeration and cupric ions in solution. High initial gold extractions were achieved in an aerated solution in the presence of cupric ions. However, these conditions simultaneously catalyzed thiosulfate degradation, resulting in gold precipitation. Therefore, it is important to establish a balance between providing sufficient air and cupric ions for fast gold dissolution, and to minimize the amount of air in the presence of cupric ions to prevent excessive thiosulfate degradation. A promising potential alternative to these conditions is a 24 hour leach without forced aeration.

Thesis/Dissertation

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2009-05-28

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http://hdl.handle.net/2429/8356

Materials Engineering

University of British Columbia

UBCV

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