Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1990-11-30
1991-11-12
Andrews, Melvyn J.
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75427, 75713, C22B 320
Patent
active
050644661
ABSTRACT:
A non-toxic process for the recovery of silver from silver containing photographic emulsion coated paper or film substrates is provided. The process includes the use of a stripping formulation comprised of an alkaline bleach solution which is capable of holding stripped animal protein, silver and silver halide in solution during separation of the substrate materials. The solution containing the silver, silver halide and animal protein is treated with a strong or highly ionized acid which results in controlled precipitation of hydrolyzed animal protein, silver and silver halide. Waste fluids are neutralized with an alkali metal hydroxide, the precipitate is dried to a sludge, carbon content of the sludge is control burned and the residue is smelted with appropriate fluxes in order to achieve silver ingot.
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patent: 3660079 (1972-05-01), Govani
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patent: 4445935 (1984-05-01), Posey et al.
patent: 4612057 (1986-09-01), Buser et al.
patent: 4765835 (1988-08-01), Schoenhard
Andrews Melvyn J.
Croskell Henry
Falk Robert Hardy
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