Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1980-03-27
1981-11-10
Williams, Howard S.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
204275, 204237, C25B 1508, C25C 120
Patent
active
042996767
ABSTRACT:
A process is provided for recovering silver and plastics material from photographic film. For exposed film, film is shredded or chopped, subjected to bleach treatment, washed, and subjected to fixing treatment, the fixing solution being circulated in closed circuit through an electrolytic silver recovery plant in which silver is deposited on one or more cathodes. For unexposed film, the bleach and washing steps can be omitted. For high silver recovery, the main fixing treatment is followed by a tailings treatment in fix solution, the tailings solution being circulated through a separate silver recovery unit of lower capacity and lower power. To maintain the fixing solution pH, a first wash in plain water is followed, before fixing, by a second wash in water treated with an alkaline chemical to raise its pH. Apparatus for performing the process may include bleach, wash and fixing towers through which material falls from chamber to chamber under control of sliding plate valves; or, a carousel can rotate baskets of film material stepwise from station to station, the carousel being carried by a ram for lowering and raising the baskets so that they can be immersed in treatment tanks at the stations and then drain; or a raised treatment vessel can be connected to solution tanks at a lower level by a pipe manifold, with pumps and valves arranged so that the solutions can be successively pumped up into the treatment vessel and allowed to drain back into respective tanks.
REFERENCES:
patent: 3510413 (1970-05-01), Lindau
Bentley James S.
Skinner John H.
Photographic Silver Recovery Limited
Williams Howard S.
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