Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Patent
1983-07-15
1984-03-20
Meros, Edward J.
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
75109, 75 83, C22B 1100
Patent
active
044378890
ABSTRACT:
Silver is recovered from photographic wastes, whether liquid (used developing solution) or a solid (used film) in a completely nonelectrolytic system using a series of physical-chemical reactions. With liquid wastes this is done by first heating them above ambient temperature to a temperature between 45.degree. C. and 65.degree. C. and then mixing them with aqueous nitric acid at a concentration of 65% and having a specific density of 1.40 g/ml. The quantity of nitric acid used forms a liquid: acid ratio with the liquid being treated of between 1:10 and 1:6. The mixture is then allowed to macerate for between 0.7 and 1.5 hours while it is continuously filtered. The filtration residue is then subjected to a second heating to about 600.degree.-700.degree. C. until it turns gray, then it is fused in a closed furnace. The fused product is then dumped directly into water to solidify and produce pure silver. For solid wastes the digestion with nitric acid takes place before calcining the solid materials. This produces a carbonaceous residue which is pulverized and diluted with the nitric acid as with liquid wastes.
REFERENCES:
patent: 2131072 (1937-04-01), Reid et al.
patent: 2944886 (1960-07-01), Fisher et al.
patent: 3929466 (1975-12-01), Maynahan et al.
Mellor J. W., Inorganic and Theoretical Chemistry, Jul. 1935, vol. 3, p. 324.
Dubno Herbert
Meros Edward J.
Ross Karl F.
Stoll Robert L.
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