[pure-silver] Re: "Green" Developer
- From: "Steven Kershaw" <stevendidit@xxxxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 29 Nov 2009 12:34:56 -0800
Silver recovery is actually a pretty simple process. Silver in solution is
more reactive than iron and recovery cartridges are no more than exchange
columns. It takes a large enough container full of very fine steel wool and
a sufficient time period for the silver in solution to chelate out. The
silver becomes a solid the iron or steel in essence "rusts out" the
remaining sludge is a silver coating on the wire that can be smelted out.
Take a 5 gal. plastic pail with a tight sealing lid, put an inflow port on
the side down at the bottom and an outflow in the top an inch or so below
the lid. Using gravity, place another bucket with a outflow at the bottom
connected to the inflow at the bottom of the first bucket. Very important is
it will need a flow constricting device such a as valve to slow the flow of
liquid to barely a trickle. The device KOADAK sold was a piece of PVC about
two and a half inches long that the hose fit snugly over and had a hole
running through it that was about a 1/16 of an inch in diameter (pipe about
an inch in diameter with a 1/16" opening). Place it at least the height of
the bucket above the bucket with the steel wool in it. Fill the "system"
with water until it flows out your outflow tube. (You can do this without
the restrictor in place) Now just poor your silver laden fixers or
bleach/fix, BLIX if you're running transparency or Ilfochrome into the upper
bucket. It will slowly trickle through the steel wool container and remove
99.+ % of the silver. Commercially we had two cartridges in series of steel
wool to make sure no silver was remaining in solution but that was just to
make the EPA happy. How long will it last will depend on your use but our
commercial lab running 60 to 70 rolls of 35mm film a day through it would
exhaust a cartridge in about 6 to 9 MONTHS! So for the home darkroom that
could mean a lifetime! You can buy silver test paper (much like pH testing
paper) or use the "plating method" described earlier by another poster.
Take a cup of solution from your outflow and place a penny in it check it
the next day if it shows signs of plating you're probably due for a change.
So start over and drain the solution still in the bucket into a new
container of steel wool, it will quickly de-sliver the solution and you are
of an running again. I can draft a drawing if someone is truly interested
in building a system. As for other solutions none were deemed harmful
enough or used in sufficient quantity to pose a risk such that the EPA was
establishing any controls. This was based on two things. First is the
concern for heavy metals that are "known to be a risk hazard" and secondly
chemicals that were "inorganic carcinogens" that would not naturally
breakdown quickly. Most photo related chemicals with the exception of
silver laden solutions did not meet threshold levels so were not being
monitored or regulated.
One thing I would ask you to bear in mind is that my experience is now some
three to four years past as I closed my lab in 2005. If anything the
significant reduction in the amount of film being processed has dropped off
so dramatically that few if any "systems would be at risk for reaching
threshold levels that would require action. Of far greater concern these
days are the micro-organisms that thrive in water systems that are resistant
to typical treatment and purification processes. Portland Oregon just this
week announced that ALL Westside city water should not be consumed without
boiling for ten minutes because E. coli had been detected above the
acceptable threshold level. (suspected causes... an animal had died and
been washed into the system or fecal contamination, both very difficult
events to transpire considering the "closed Loop" nature of today's water
systems.
Good luck!
Steven
The beautiful north Oregon coast.
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your
account (the same e-mail address and password you set-up when you subscribed,)
and unsubscribe from there.
Other related posts:
