Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Patent
1987-04-07
1988-10-18
Stoll, Robert L.
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
75101R, 75101BE, 75103, 75108, 75115, 423 24, 423 27, 423 33, 423 34, 423 36, 423 41, 423 43, 423 45, 210702, 210711, 210729, 204109, C22B 1104
Patent
active
047785195
ABSTRACT:
A method is provided for recovering gold and silver from precious metal bearing materials including ores, leaching residues, flue dust, electronic scrap, jewelry scrap, etc. In the method, the gold and silver are extracted from the precious metal bearing materials with a thiourea solution to form a thiourea leach, and the thiourea leach is contacted with carbon to adsorb the gold and silver and provide loaded carbon. The method is characterized by the step of contacting an alkaline solution of thiousulfate ion with the loaded carbon thereby desorbing the precious metals form the carbon. In one modification of the method, an additional step includes adding a salt to the aqueous thiousulfate solution. When needed, the method includes the step of protecting the thiousulfate ion from oxidizing agents. This is done by adding a reducing agent such as sodium sulfite to the thiousulfate solution. When copper is present, the method includes the addtional step of removing copper from the carbon prior to exposing the carbon to the thiourea solution containing the precious metals.
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Stoll Robert L.
Towsend Marvin S.
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