Date: Tue, 9 Nov 1999 10:28:05 EST
Subject: Re: Photographic silver recovery
You sill have to forward this response:
There are two opportunities to recover silver from photoprocessing. The first
would be from the processing solutions, specifically the fix and washwater.
The second is from the developed film itself. Recovering silver from the fix
can be accomplished by using an electrodepositon unit where the silver is
plated out of solution onto the cathode. These units are about 95% efficient.
Chemical recovery cartridges or "steel wool buckets" can also be used in
conjunction with an electrodepositon unit or as stand-alone units. These
units are not good in low flow or batch recovery situations as they tend to
channel and loose efficiency. These units are about 99% efficient.
For washwater the use of an ion exchange unit is good for automatic film
processors or for tray developing, it would be better to use an
electrodepositon unit. Using silver recovery on the washwater needs to be
closely examined as there is not a significant amount (3-5 ppm) amount of
silver in the washwater as compared to 3,000-5,000 ppm in the fix.
Recovering silver from the exposed film is more time consuming and requires
the use of a special process. There are two approaches, one is more toxic
than the other as it involves burning the film and recovering the silver with
cyanide. The other technique is less toxic as it uses an enzyme to remove the
emulsion from the film based and the silver is recovered from the removed
emulsion. I am not aware of any "kits" that would allow you to recover silver
from the exposed film at home.
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